RaspberryPiBlueprints

TableofContents

RaspberryPiBlueprints

Credits

AbouttheAuthor

AbouttheReviewers

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Supportfiles,eBooks,discountoffers,andmore

Whysubscribe?

FreeaccessforPacktaccountholders

Preface

Whatthisbookcovers

Whatyouneedforthisbook

Whothisbookisfor

Conventions

Readerfeedback

Customersupport

Downloadingtheexamplecode

Downloadingthecolorimagesofthisbook

Errata

Piracy

Questions

1.RaspberryPiPirateRadio

Whatyouwillneed

SettingupthePi

ChoosingaLinuxdistribution

WritinganSDcard

Windows

LinuxandMacOS

BootingthePiforthefirsttime

Networkscanning

ConnectingtothePiviaSSH

CommonLinuxcommands

Theinitialsetup

Settingupthepirateradio

TransferringMP3filestothePi

Scriptingamediaplayer

CallingPiFMfromPython

SearchingforMP3files

Gettinginputfromacommandline

Queuingthemediafilestobeplayed

Usingthemediaplayerscript

Summary

2.PortableSpeakerSystem

Whatyouwillneed

Toolsyouwillneed

SettingupLogitechMediaServer

SettingupthePiasaSqueezeboxclient

SettingupWi-FionthePi

Runningsqueezeliteasadaemon

Buildingtheelectronics

Theamplifiercircuit

Runningthespeakersystemonbatterypower

Buildingtheenclosureforthespeakersystem

RunningLogitechMediaServeronthePi

CreatingabackupimageofanSDcard

AutomountingaUSBstoragedevice

InstallingLogitechMediaServer

SettingupthePiasaWi-Fiaccesspoint

Summary

3.MiniRetroArcadeCabinet

Requirements

Settinguptheinputelectronics

Buildingthecabinet

SettingupPiPlay

UsingthebuttonsandjoystickwithPiPlay

Summary

4.GPS-enabledTime-lapseRecorder

Whatyouwillneed

Settingupthehardware

Thecameraboard

ConnectingthecameramoduletothePi

SettinguptheRaspberryPicamera

TheGPSmodule

Settingupthecapturesoftware

Usingthecaptures

Creatingatime-lapsevideo

ExportingGPSdataasCSV

Summary

5.HomeTheaterPC

Whatyouwillneed

SettingupOpenELEC

Thefirstbootandinitialsetup

ConnectingthePitoawirelessnetwork

UploadingmediafilestothePi

Windows

Linux

ShuttingdownthePi

SettinguptheLCD

Settinguptheswitches

Finalassembly

Summary

6.OutdoorWeatherStation

Whatyouwillneed

ReverseengineeringtheMaplinsensors

Understandingthesensors

Wiring

SettingupyourArduino

Settinguptheremainingsensors

DHT11/22

BMP180

Theweatherstationwebapplication

DeployingtheapponthePi

Takingreadingsfromthesensors

Assemblingtheweatherstation

Usingthewebapplication

Summary

7.HomeSecuritySystem

Whatyouwillneed

Thesecuritysystemstructure

Designingyoursecuritysystem

Webapplications

Deployingourapplication

Configuringsensorsandalarms

Interfacingsensors

ThePIRmotionsensors

Magneticdoorsensors

TheRFnetwork

SettinguptheRaspberryPi

SettingupArduino

Troubleshooting

Summary

8.Remote-operatedRoboticArm

Whatyouwillneed

Driveelectronics

Settingupthecamera

Deployingwebapplications

Thearmandchassisconstruction

Calibration

Chassismotors

Arm2andhandservos

Thearm1servos

Troubleshooting

Thevideostreamhasasubstantialdelay

Theservosmakealoudhummingnoise

Controloftherobotislost

Thearmjumpstonewpositions

Summary

9.MagicMirror

Whatyouwillneed

Toolsyouwillneed

Theory

Thewebapplication

Developinganewwidget

ThePythoncode

TheJinjapagetemplate

TheJavaScriptcode

ThePisetup

Rotatingthedisplay

Deployingthewebapplication

SettingupChromium

Enclosureconstruction

Buildingthemirrorwithoutanenclosure

ThePienclosure

Configuration

Widgets

Includedwidgets

Exampleconfigurations

bbc_ticker.conf

clock.conf

Styles

Troubleshooting

Thewebapplicationfailswiththe500InternalServerError

Thedisplaydoesnotwork

Summary

10.BottleXylophone

Whatyouwillneed

Assemblinganotebottle

Electronics

Thewebapplication

Configuration

Tuning

Testing

Troubleshooting

Notesaremissed

Servosdonotmovecorrectly

Summary

Index

RaspberryPiBlueprints

RaspberryPiBlueprintsCopyright©2015PacktPublishing

Allrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.

Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyoftheinformationpresented.However,theinformationcontainedinthisbookissoldwithoutwarranty,eitherexpressorimplied.Neithertheauthor,norPacktPublishing,anditsdealersanddistributorswillbeheldliableforanydamagescausedorallegedtobecauseddirectlyorindirectlybythisbook.

PacktPublishinghasendeavoredtoprovidetrademarkinformationaboutallofthecompaniesandproductsmentionedinthisbookbytheappropriateuseofcapitals.However,PacktPublishingcannotguaranteetheaccuracyofthisinformation.

Firstpublished:March2015

Productionreference:1200315

PublishedbyPacktPublishingLtd.

LiveryPlace

35LiveryStreet

BirminghamB32PB,UK.

ISBN978-1-78439-290-1

www.packtpub.com

CreditsAuthor

DanNixon

Reviewers

SoumenChandraLaha

MaryalaSrinivas

CommissioningEditor

AkramHussain

AcquisitionEditor

MeetaRajani

ContentDevelopmentEditor

ShubhangiDhamgaye

TechnicalEditor

SiddhiRane

CopyEditor

NehaVyas

ProjectCoordinator

HarshalVed

Proofreaders

SimranBhogal

MariaGould

PaulHindle

Indexer

MariammalChettiyar

ProductionCoordinator

ManuJoseph

CoverWork

ManuJoseph

AbouttheAuthorDanNixonlivesinEnglandandisa20-yearoldsoftwareengineeringstudentwhoiscurrentlystudyingatNewcastleUniversityandisinhisthirdyear.Hehaslonghadaninterestinelectronicsandembeddedcomputingprojects.

Previously,Danhasworkedona360-degreecamerasystemfortheRaspberryPiandthisiswherehisinterestintheplatformstarted.

Currently,heisonayear-longworkplacementandisworkingonneutrondataanalysissoftwareattheRutherfordAppletonLaboratoryinOxford,UK.

Iwouldliketothankmymotherandfatherfortheirsupportwhilewritingthisbook.IwouldalsoliketothankthemembersofMakerSpace,Newcastle,forprovidingthefacilitiestoprototypetheprojectsandallowingmetousesomeoftheirprojectsinthisbook.

AbouttheReviewersSoumenChandraLahahasbeenworkingasaseniorembeddeddesignengineeratWineYardTechnologiessince2008.Hestartedhiscareerasaqualitycontrolengineerandgraduallybecameanembeddeddesignengineer.Hehasbeenworkinginthefieldofembeddedsystemsandhasindustryexperienceofmorethan6yearsinvariousdomains,includingautomotive,consumerelectronics,healthcare,andsoon.Hehashands-onexperienceinvariousmicrocontrollersandmicroprocessors,suchas8051,PIC,AVR,PSoC,ARMCortex,ARM7,ARM9,ARM11,andtheTI-DSPmicrocontroller.HehasdevelopmentexposuretoembeddedLinuxandWindowsCEandknowshowtoportreal-timeoperatingsystemsonvariousARMplatforms.

Heisanelectronichobbyistanddesignerandbelievesincontinuouslearning.Hisstrengthslieindeveloping,maintaining,integrating,anddebugginglargesizedCcodeofapplicationsandsystem-levelembeddedsoftwaredesigns.

MaryalaSrinivasisthefounderandmanagingdirectorofWineYardTechnologies,whichwasfoundedin2006.Hehasover10yearsofexperienceinthefieldofadvancedembeddedsystemsdesignanddevelopment.Heisapassionateandenthusiasticentrepreneur.HispassiontobecomeanentrepreneurmadehimrejectagreatjobofferfromDelhiMetroRailCorporation(DMRC),wherehewastoworkforthesignalingdepartmentintheR&DDivision.HeisassociatedwithJuniorChamberInternational,IndiaandHyderabadDirectors/CEO’sForum(HDCF).HereceivedtheIndiraGandhiSadbhavanaAwardin2012foroutstandingservices,achievements,andcontributionstothenationinthefieldofscienceandtechnology.

Manyofhisarticlesarepublishedinnationalandinternationaljournalsandtechnicalmagazines.HehasaddressedseveraltechnicalconferencesandseminarsinthefieldofembeddedsystemsandRTOSdesign.HewasrecognizedasthestarspeakeratEFYDesignEngineers’Conference,heldatNewDelhiinMarch2012.ManyofthefacultymembersfromuniversitiessuchasNITs,JNTU,AU,andOUandotherprivateengineeringcollegesbenefitedimmenselybythetechnologytalenttransformationworkshopsconductedbyhimatWineYardTechnologies.TheWineYardteamledbyhimhasachievedmanymilestones.Morethan100,000studentsandover400professionals,includingtheteachingfacultyfromuniversitiesandmanyworkingengineers,haveimmenselybenefitedfromthetalenttransformationprograms.

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PrefaceTheRaspberryPiisasmallformfactor,singleboard,ARM-basedcomputer.ItiscapableofrunningonmanydesktopapplicationsthatcanberunonastandardLinuxcomputer.WhilethePiisonlyslightlylargerthanacreditcard,itusesverylittlepower.Assuch,ithasbecomeverypopularamongthehackerandmakercommunity,whichusesthePitointegratemorecomputingpowerintheirprojects.

ThePiisveryeasytosetupandinlessthan20minutes,youcanrunitonamodifiedversionofpopular,Linux-basedoperatingsystems.ItwillfunctionjustlikeyouwouldexpectadesktopPCto.Thankstoitssmallformfactor,manypeoplehaveuseditasanalternativetoatraditionalPCforfastaccesstoapplicationsandtheInternet.SincethePidrawsverylittlepower,itcanbeleftrunning.

WherethePireallyexcelsisthatitbringsmorecomputingpowertohardwareandelectronicsprojects.ThisismadepossiblebyawiderangeofinterfacesonthePithataretypicallynotfoundonconventionalcomputers.

ThishasledtoariseinnewprojectsthataremadeusingthePi,whichotherwisewouldhavebeenconsiderablymoredifficultorexpensivetomake.

WhatthisbookcoversChapter1,RaspberryPiPirateRadio,introducesthePiandgivesanoverviewofitssetupandconfigurationprocedureandsomefundamentalLinuxconcepts.ThischapterthendemonstratesthebasicuseoftheGPIOheaderandPythonscripting.

Chapter2,PortableSpeakerSystem,exploreshowtousethePiasaportable,battery-poweredspeakersystemwithaself-containedmediaserverthatcanbeusedwithoutanytiestoapowersupplyorhomenetwork.

Chapter3,MiniRetroArcadeCabinet,demonstrateshowthePicanbeusedtocreateaminiarcadecabinetcompletewithatraditionaljoystickandbuttoncontrolsandhowitcanbeusedtoplayarangeofclassicarcadeandconsolegames.

Chapter4,GPS-enabledTime-lapseRecorder,covershowtousethePiasatimelapserecorderthatcanalsocapturethelocationofeachimageandtriggertheimagecapturebasedonthecurrentpositionofanddistancetraveledbythecamera.

Chapter5,HomeTheaterPC,exploresthewayinwhichthePicanbeusedasahometheaterPCusingthepopularXBMCmediacentersoftwareandacustom,purpose-builtenclosure.

Chapter6,OutdoorWeatherStation,delvesintothetopicofinterfacinghardwaretothePiusingintermediatedevices,inthiscase,Arduino.WealsotakealookatPythonwebapplicationsrunningonthePi.

Chapter7,HomeSecuritySystem,exploreshowtousethePiasahubforawirelessnetworkofsensorsandhowthisdatacanbeusedanddisplayedonawebapplication.

Chapter8,Remote-operatedRoboticArm,focusesonhowtousethePitocontrolandmonitordevicesremotelyintheformofaroboticarmthatcanbecontrolledthroughawebapplication.

Chapter9,MagicMirror,expandsyourknowledgeofwoodworkinganddesigning,whichwillprovetobeimportantskillsforanyfurtherprojectsthatyoudointhefieldofelectronicsandphysicalcomputing.

Chapter10,BottleXylophone,covershowthePi,severalservos,andsomeemptybottlescanbeturnedintoamusicalinstrumentdrivenbyMIDIfiles.

WhatyouneedforthisbookThisbookassumesthatyouarefamiliarwiththebasicsoftheRaspberryPiandLinux.MostofthecodeinthisbookisinPythonwithsomeC++.However,thesourcecodeforeachoftheprojectsisavailablealongsidethebookthatcanbeusedstraightonthePi.

Severaloftheprojectswillalsodealwithsomebasicelectronics,andassuch,somebasictoolswillbeneededforthecompletionofsomeprojects.However,notethatatthestartofeachchapter,theproceduretobuildtheelectronicssideoftheprojectisexplainedstepbystep.

Someprojectswillalsorequireaccesstowoodworkingtoolsinordertoconstructcasesandenclosures.Usually,youwillrequirejustthecommon“gardenshed”tools.However,thereisinformationintherelevantchaptersonwhatyoucandoifnothavingthecorrecttoolscausesanissueintherelevantchapters.

WhothisbookisforThisbookisaimedatthosearejustgettingstartedwiththeRaspberryPi,alreadyhaveafewsmallprojectsundertheirbelt,andarelookingtogetintotheworldofhardwareandphysicalcomputingprojects.

ConventionsInthisbook,youwillfindanumberoftextstylesthatdistinguishbetweendifferentkindsofinformation.Herearesomeexamplesofthesestylesandanexplanationoftheirmeaning.

Codewordsintext,databasetablenames,foldernames,filenames,fileextensions,pathnamesdummyURLsanduserinputareshownasfollows:“Wherepath/to/raspbian_image.imgistheextractedimagefileandsdXisthepathtoyourSDcard.”

Ablockofcodeissetasfollows:

#!/bin/bash

sleep20

cd/home/pi

pythonplayer.py-dmusic--random-f99.9&

Anycommand-lineinputoroutputiswrittenasfollows:

ffmpeg-ifile.mp3-fs16le-ar22.05k-ac2-|sudo./pifm-freq22050

stereo

Newtermsandimportantwordsareshowninbold.Wordsthatyouseeonthescreen,forexample,inmenusordialogboxes,appearinthetextlikethis:“Filescanbeuploadedbyright-clickingonthemandselectingUpload.”

NoteWarningsorimportantnotesappearinaboxlikethis.

TipTipsandtricksappearlikethis.

ReaderfeedbackFeedbackfromourreadersisalwayswelcome.Letusknowwhatyouthinkaboutthisbook—whatyoulikedordisliked.Readerfeedbackisimportantforusasithelpsusdeveloptitlesthatyouwillreallygetthemostoutof.

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ErrataAlthoughwehavetakeneverycaretoensuretheaccuracyofourcontent,mistakesdohappen.Ifyoufindamistakeinoneofourbooks—maybeamistakeinthetextorthecode—wewouldbegratefulifyoucouldreportthistous.Bydoingso,youcansaveotherreadersfromfrustrationandhelpusimprovesubsequentversionsofthisbook.Ifyoufindanyerrata,pleasereportthembyvisitinghttp://www.packtpub.com/submit-errata,selectingyourbook,clickingontheErrataSubmissionFormlink,andenteringthedetailsofyourerrata.Onceyourerrataareverified,yoursubmissionwillbeacceptedandtheerratawillbeuploadedtoourwebsiteoraddedtoanylistofexistingerrataundertheErratasectionofthattitle.

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Chapter1.RaspberryPiPirateRadioInthischapter,wewilltakeaquicklookattheRaspberryPihardwareandsomeofthesoftwarethatwillbeusedbothinthisprojectandthemajorityofothersthroughoutthisbook.

AsthePiwasbasedonhardwarethatwastobeincludedinembeddedorportableelectronics(suchassmartphonesandtablets),ithasafewextrahardwarefeaturesthatarenotfoundonatypicaldesktoporlaptopPC,oneofwhichistheGeneralPurposeInputandOutput(GPIO)header.Thisisasetofpins(26onthemodelAandB,and40onthemodelB+)thatallowsyoutocommunicatewithexternalhardwaresuchasGPSsensors,accelerometers,andmotorsthroughprogramminglanguagessuchasPython,C,andC++.Whenwegetfurtherinthischapter,wewilltakealookatalittletrickthatcanbedonetoturnoneofthesepinsintoanFMradiotransmitter.

WhatyouwillneedYouwillneedthefollowing:

TheRaspberryPiandpowersupplyAnSDcardwithatleast4GBmemory(16GBisrecommendedasitholdsagoodamountofmusic)AthickwireorFMradioantennaMaletomale0.1inchpinjumperwires

SettingupthePiInordertogetthePiupandrunning,thebareminimumyouwillneedisaUSBpowersupply,microUSBcable,anEthernetcabletoconnectthePitoyournetwork,andanSDcardthathasatleast4GBmemory.Although,lateron,someprojectswillneedalargercapacityoftheSDcard.

Whileamonitor,mouse,andkeyboardcanalsobeusedforalotoftheprojectsinthisbook,theyarenotactuallyrequiredassumingthatyouhaveanetworkthatrunsaDHCPserver,whichyoucanconnectwiththePiinordertosetitupoverSSH.

ItisworthmentioningnowthatforaUSB-powereddevice,thePiisquitepower-hungry(drawingaround600-700mA),therefore,whilethePicanbepoweredfromaUSBport,whichisusuallyratedforaround500mA,itisrecommendedthatyouuseamainspoweredadapter.Withoutthis,thePicanbecomeunstablewhenadditionaldevicesareconnectedthatdrawmorepower,forexample,aUSBWi-Fidongleorcameramodule.

ChoosingaLinuxdistributionThereareawiderangeofLinuxdistributionsavailableforthePi,someofwhichareverygeneralpurposewhileothersarebuiltforspecificpurposes(acoupleofwhichwillbeusedinthelaterprojectsofthischapter).Fornow,wewillusethemoststandarddistribution,Raspbian,whichasthenamesuggestsisbasedontheDebiandistribution.

NoteTheRaspberryPidownloadspage(http://www.raspberrypi.org/downloads)hasagoodselectionofgeneralpurposedistributions.

AnotherrelativelynewdistributionthatisworthmentioningisMinibian(http://minibianpi.wordpress.com),adistributionbasedonRaspbian,whichhasthemajorityofitsdefaultsoftwareremoved.Whilethismaynotseemthathelpful,itmeansthatthePibootsinauseableOSinaround25secondsandsavestheSDcardspace.ThistypeofOSismoresuitedtoaprojectthathasfinishedbeingdevelopedandisgoingintoamorenaturalusageenvironment.YouusuallywouldnotexpectaWi-Firoutertotake3minutestoboot,sowhyshouldyourPi-basedInternetradio?

WritinganSDcardWhenyouhavealltherelevanthardware,headovertohttp://www.raspberrypi.org/downloadsanddownloadtheZIParchiveforRaspbianandextractit.

Thenextstepsvarydependingonyouroperatingsystem.

WindowsWindowsdoesnotnativelyincludeatoolusedtowritediskimages,therefore,theWin32DiskImager(http://sourceforge.net/projects/win32diskimager)applicationisusedtowriteimagestoanSDcard.

First,gotothedownloadlinkmentionedintheprecedingparagraph,download,andinstallWin32DiskImager.Aswritingimagestodrivesrequiresadministratorpermissions,youwillneedtorunWin32DiskImagerbyright-clickingonitsentryintheStartmenu,andselectingRunasadministrator:

Next,selectthe.imgfilethatwasextractedfromtheRaspbianZIPfileusingthefoldericonunderImageFileandthedriveletteroftheSDcardfromthedrop-downbox:

NoteEnsurethatthecorrectdriveletterisselected,andtheSDcarddoesnotcontainanydatathathasnotbeenbackedup,asthisoperationwilldestroyallofthedataalreadypresentinthecard.

Finally,clickonWritetowritetheimagetotheSDcard.

LinuxandMacOSUnixandUnix-likeoperatingsystemsalreadyhaveatooltoreadandwriteimagestoexternalstorage—dd.

First,youwillneedtofindthepathforyourSDcard.Theeasiestwaytodothisistousetheudevmanagementtool,udevadm,tomonitortheudevlog,whichlogsactivityfromvariousdevicesonthesystem,includingtheSDcardbeinginsertedandwillallowyoutoseethedevicepaththatwasassignedtoitandthepartitionsalreadyexistingonit.Thiscanbedonebyrunningthefollowingcommand:

udevadmmonitor--udev

Then,inserttheSDcard,atwhichpoint,youshouldseeasetoflogmessagessimilartotheonesshowninthefollowingscreenshot:

Here,theimportantinformationcanbeseenonthelastthreelines,whichtellsusthatin

thiscase,thepathfortheentirecardis/dev/sdb,withtwopartitionsat/dev/sdb1and/dev/sdb2.

WemustnowensurethatnoneofthesepartitionsontheSDcardarecurrentlymounted,assomedesktopmanagers(suchasGNOME,thedefaultdesktopmanageronUbuntu)willtrytoautomaticallymountpartitionswhentheyaredetected.

Todothis,wewillrunthefollowingcommandforeverypartition(thatis,inmycase,/dev/sdb1and/dev/sdb2),wherePATHisthepathtothepartition:

umountPATH

Ifthepartitionwasmounted,youwillnotseeanyoutputfromthecommand;however,ifthepartitionwasnotmounted,youwillgetthefollowingmessage:

OnceyouknowthepathforyourSDcardandhaveensuredthatnoexistingpartitionsaremounted,youcanthenwritetheRaspbianimagetoyourSDcardusingthefollowingcommand,wherePATHisthepathtotheSDcard(/dev/sdbinmycase):

sudoddif=path/to/raspbian_image.imgof=PATH

NoteBecertainthatthepathtotheSDcardiscorrect,andthecarddoesnotcontainanydatathathasnotbeenbackedupasthisoperationwilldestroyallofthedataalreadypresentonthecard.

Wherepath/to/raspbian_image.imgistheextractedimagefileandsdXisthepathtoyourSDcard.Notethatthisstepcantakeupto5-8minutes,sincenooutputisgivenonthescreen,theSDcardreader’sbusy/dataLEDisagoodindicationthattheimageisbeingwritten.

TipSincetheGNUCoreutils(whichincludecommandssuchascp,mv,dd,andsoon)donotprovidemuch(orany)outputtoindicatetheprogress,youmaywanttotakealookattheCoreutilsViewertool(https://github.com/Xfennec/cv),whichshowstheprogressoftheCoreutilscommands.

BootingthePiforthefirsttimeOnceyouhavetheimagewrittentothecard,itistimetobootthePiandperformtheinitialsetup.Themostcommonwaytodothisisbyusingakeyboard,mouse,andmonitor;however,ifyouhaveaccesstoanetworkthatprovidesDHCP(asmosthomenetworksdo),thenthesetupcanbedoneentirelyoverSecureShell(SSH).

First,setupthehardwareandbootthePibyinsertingtheSDcard,connectingthepower,andtheEthernetcable.Withinafewseconds,youwillseethattheACTLEDstartstoflicker.Ifitflashesforveryshortpulsesordoesnotlightatall,thenthisindicatesanissuewitheithertheSDimage,theconnectionbetweenthecardandthePi(acommonissueforthemodelsAandB),orthecarditself.

OncethePihasbooted(indicatedbylessfrequentflashingoftheACTLED),youwillneedtodetermineitsIPaddress.Therearetwomainwaystodothis:byaccessingtheDHCPallocationsviayourrouterorbyscanningthelocalnetwork.

NetworkscanningThecross-platformtool,theNmaputility(http://nmap.org)canbeusedtoscananetwork.

Todoso,youwillneedtofindtheIPaddressofyourPC(inordertofindthesubnetonyourlocalnetworktosearchforthePiin).OnWindows,thiscanbedonebyopeningtheCommandPromptandexecutingthiscommand:

ipconfig

Thisshouldgiveyoutheinformationaboutyournetworkinterfacessimilartothefollowing:

OnUnix,thiscanbedonebyusingthefollowingcommand:

ifconfig

Thiscommandgivesoutputsimilartothefollowing:

ThesearchIPrangethatisgiventoNmapisobtainedbyreplacingthelastnumberofIPv4orInetAddresswith*.Inourcase,itwillbe192.168.0.*.

Nowthatweknowtheaddressrangeinwhichwewillbelooking,wecanopenaterminalandrunthefollowingcommand:

nmap--open192.168.0.*

ReplacingtheIPrangewithyoursearchrangewilltrytomakecontactwitheveryhostinthegivenIPaddressrangeandwillreturnwithalistofeveryhostthatisup,withalistoftheiropenports,andwhatservicestheycorrespondto.Inourcase,wearelookingforanyhoststhathaveanopenSSHport:

StartingNmap5.21(http://nmap.org)at2014-09-2111:58BST

Nmapscanreportfor192.168.0.8

Hostisup(0.0064slatency).

Notshown:999closedports

PORTSTATESERVICE

22/tcpopenssh

Nmapdone:256IPaddresses(5hostsup)scannedin5.84seconds

Here,IhaveonlyshownthereportforthePi.Usually,afterthefirstboot,SSHwillbethe

onlyservicethatisstarted,soitisusuallygivenawayasthedevicethatonlyprovidesSSH.

ConnectingtothePiviaSSHOnUnix,accessingthePiviaSSHisassimpleasexecutingthefollowing:

sshpi@[PiIP]

Here,PiIPistheIPaddressofthePi.Youmaygetawarningsimilartothisthefirsttimeyourunthecommand:

Theauthenticityofhost'192.168.0.8(192.168.0.8)'can'tbeestablished.

ECDSAkeyfingerprintis32:4c:46:1b:dd:7e:8b:52:a0:31:c3:f5:9f:73:d1:c6.

Areyousureyouwanttocontinueconnecting(yes/no)?

ThiscansafelybeignoredbytypingyesandpressingEnter.Youwillthenbeaskedforapassword,andasthisisthefirstboot,thedefaultisraspberry.

OnWindows,PuTTY(http://www.putty.org)canbeusedtoSSHintothePi.Oncedownloaded,runPuTTYandentertheIPaddressofthePiandtheHostNamefield,ensuringthatPortissetto22andSSHisselected.Then,clickonOpen:

Youwillseeawarningmessagesimilartothefollowingabouttheidentityofthehost:

Again,thiscanbeignoredbyclickingonYes.YouwillthenbeaskedforausernameandpasswordinthePuTTYterminalwindow.Sincethisisthefirstboot,thedefaultsarepiandraspberry.

CommonLinuxcommandsAtthispoint,itwouldbegoodtolearnafewLinuxshellcommands,whichyouwillnodoubtcomeacrosswhileworkingwiththePi:

cd:Thechangedirectorycommandsetstheworkingdirectorytoagivendirectory,forexample,cd/home/pils:Thelistcommandliststhecontentsofthecurrentworkingdirectorymkdir:Themakedirectorycommandcreatesanewdirectorywithinthecurrentworkingdirectory,forexample,mkdircodecat:Theconcatenatecommandcanperformoperationsontextfiles,anditcanalsodisplayitscontentsontheconsole,forexample,cat/etc/passwdpwd:Theprintworkingdirectorycommandtellsyouthedirectoryyouarecurrentlyinchmod:Thechangemodecommandchangestheaccesspermissiontoafile,forexample,chmod744file(thisgivesread,write,andexecutepermissionstotheowner,andread-onlypermissiontoeveryoneelse)sudo:Thesuperuserdocommandexecutesthefollowingcommandsasroot,forexample,sudoapt-getupgrademv:Themovecommandmovesthefileordirectoryinthefirstargumenttothesecond,forexample,mvfile.txtmisc_filescp:Thecopycommandcreatesacopyofafileordirectoryinanotherdirectory,forexample,cpfile.txtmisc_files/file2.txtrm:Theremovecommanddeletesafile,forexample,rmfile.txt

Moreinformationcanbeobtainedaboutagivencommandviaitsmanpage,whichcanbeaccessedusingthefollowingcommand,wherecommandisthecommandyouwishtoknow

moreabout:

mancommand

TheinitialsetupOnceyouareabletoSSHinthePi,runtheconfigurationutilityusingthefollowingcommand:

sudoraspi-config

ThisutilityallowsyoutoconfigurethePihardwareandperformusefulconfigurationtaskssuchaschangingpasswordsandresizingtherootpartitionontheSDcard,bothofwhich,wewilldonow.

First,selecttheExpandFilesystemoptionandpressEnter.Theutilitywillmodifythepartitiontableandreportthatithascompleted,andthatthechangesmadewillonlyaffectthefilesystemafterthenextreboot.PressEnteragaintoreturntothemainmenu.

Now,selectChangeUserPasswordandhitEntertwice.Youwillbetakenbacktotheshellandpromptedtoenteranewpassword,whichhastobeenteredtwice.Oncedone,aconfirmationboxwillnotifyyouthatthepasswordwaschangedsuccessfully;pressEntertoreturntothemenu.

Asthisisallthatneedstobedoneinraspi-configfornow,presstheleftarrowkeytwicetoselectFinishandEntertoconfirm.Youwillbeaskedwhetheryouwanttorebootnow;selectYesandpressEnter.OncethePiisrebooted,SSHbackintoitusingyournewpassword.

Onceyouhaveaccessagain,checkwhetheryounowhaveaccesstothefullstoragespaceontheSDcardusing:

df-h

ThecommandshouldreportthesizeofrootfsmuchclosertotheSDcardcapacity:

rootfs16G2.5G13G17%/

AllthatislefttodonowistomakesurethatthesoftwareonthePiisuptodate.Sinceweareusinganimagethatwasjustdownloaded,itisnotlikelythattherewillbealargenumberofupdates;however,itisagoodpracticetokeepaninstallationuptodate.

Runningthefollowingcommandswillfirstupdatethelistofavailablepackagesthenupdateanyinstalledpackageswithnewerversionsthanwhatwasinstalled:

sudoapt-getupdate

sudoapt-getupgrade

Notethatthisprocesscantakeupto10minutesdependingonthenumberofupdates,andusuallytakeslongerthanadesktopPCorlaptopasthisprocessiswritingtoanSDcardratherthanatraditionalharddrive.

SettingupthepirateradioIt’snowtimetodownloadandsetupthePiFMsoftware,whichwillallowyoutousetheGPIOheaderasanFMtransmitter.First,we’llneedtodownloadthesoftwareusingthefollowingcommands:

wgethttp://omattos.com/pifm.tar.gz

tar-xzvfpifm.tar.gz

ThiswillgetthegzippedarchivethatcontainsthePiFMsoftware,thePythonlibrary,andsometestfilesanduncompressthem.

Fornow,asinglemaletomale0.1inchpinjumperwillsufficeasanantenna;thisshouldbeconnectedtoGPIO4(pinnumber7)ontheGPIOheaderandmadetostandasuprightaspossibletoensurethebestrange(refertothefollowingimage):

YouarenowreadytotestthesetupwithanFMradio;firstly,youwillneedtochooseafrequencythatwillnotoverlapwithanylicensedbroadcastsinyourareaandiswithintheFMradiotransmissionrangeinyourarea(usuallybetween88Mhzand108Mhz).Alotof

radiosthatdoautomatictuningalsotendtopreferfrequenciesthatareamultipleof0.1MHz(forexample,99.9,101.3,andsoon).

Onceyouhavechosenyourfrequency,tuneyourradiointoit,andrunthefollowingcommandonthePi,wherefreqisthefrequencyyouwishtobroadcaston:

sudo./pifmleft_right.wavfreq22050stereo

Youshouldnowhearasampleautoclipdemonstratingtheabilitytobroadcaststereoaudio.

TransferringMP3filestothePiForourmediaplayer,wearegoingtoneedaselectionofMP3filesonthePiSDcard.Therearetwomainwaystodothis,eitherbymovingthecardbacktoyourPCandmountingitlikearegularSDcard,orbyusingtheSecureFileTransferProtocol(SFTP).

Inthiscase,sincethePiisalreadyrunning,IhaveoptedtouseSFTP.ThiscanbedoneusingtheFileZilla(https://filezilla-project.org)FTPclient.Onceinstalledandopened,enterthesamedetailsthatyouusedtoconnecttothePioverSSHinthefieldsatthetopofthewindow(using22forPort),andclickonQuickconnect.

YoushouldnowbeabletobrowsethefilesystemsofbothyourcomputerandthePi,asshowninthefollowingscreenshot.Filescanbeuploadedbyright-clickingonthemandselectingUpload.

InordertoplaythemusicyouhavejusttransferredtothePi,youwillneedtoinstalltheffmpegutility,whichisatoolthatiscommonlyusedtotranscodemediafilesandcanbeinstalledusingthefollowingcommand:

sudoapt-getinstallffmpeg

NowthatyouhavesomeofyourownmusiconthePi,youcantryplayingitbypipingthe

outputofffmpegtoPiFM:

ffmpeg-ifile.mp3-fs16le-ar22.05k-ac2-|sudo./pifm-freq22050

stereo

Here,fileistheMP3filetobebroadcastedandfreqisthefrequencytobroadcastiton.Sincewearetellingffmpegtoprovideoutputfortwoaudiochannels(-ac2)andgivingthestereooptiontoPiFM,thisshouldgiveastereoaudiobroadcast.

ScriptingamediaplayerNowthattheFMtransmitterisworking,wecanmakeitdosomethingalittlemoreuseful;inthiscase,wewilluseittobroadcastapersonalizedradiostationwithacollectionofyourownmusic.

Todothis,wewillwriteaPythonscriptthatmanagestosearchforMP3filesandcallsPiFMtobroadcastthem.

CallingPiFMfromPythonInthePiFMdownloadandonthePiFMwebsite,youmayhavenoticedthatthereisaPythonlibrarythatcanbeusedtocontrolPiFM.Although,lookingatthesourcecodeforit,youcanseethatallthelibrarycandoiscallthepifmexecutablewiththeminimumnumberofcommands,andthereforewillnotallowustoplayMP3files.

However,itisasimpleprocesstocreateourownfunctionthatwillallowustopassthefilenameofanMP3,afrequency,andthatwillallowPythontocallffmpegandPiFMinordertobroadcasttheaudiointhefileforus:

defplay_file(filename,frequency):

command='ffmpeg-i"%s"-fs16le-ar22.05k-ac2-|sudo./pifm-%f

22050stereo'%(filename,frequency)

subprocess.call(command,shell=True)

Thiscodeisanextractfromtheplayer.pyfile;allwearedoinghereistakingtheshellcommandsusedtoplayanMP3fileandreplacingthefilenameandbroadcastfrequencywithvaluesthatarepassedtothefunctionasparameters.Then,weareusingthePythonsubprocessmoduletoexecutethecommandasifitwastypedintoashell.

TipDownloadingtheexamplecode

Youcandownloadtheexamplecodefilesfromyouraccountathttp://www.packtpub.comforallthePacktPublishingbooksyouhavepurchased.Ifyoupurchasedthisbookelsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlytoyou.

SearchingforMP3filesForourscripttoplayanyMP3files,itneedstobeabletofindthemfirst.FindinganMP3fileinvolvestakingalookateachfileinastartingdirectorytocheckwhetherafileisanMP3file,andthenrepeatingthisprocessforeverydirectorywithinthestartdirectory.Thankfully,Pythonmakesthisveryeasy:

mp3_files=list()

forroot,dirs,filesinos.walk(directory):

forfilenameinfiles:

iffilename.endswith(".mp3"):

mp3_files.append(os.path.join(root,filename))

Here,directoryisthedirectorywewanttosearchforfilesmediain.Theos.walkfunctionreturnsatuple;thefirstelement(root)isastringthatcontainstheabsolutepathtothesearchdirectory,dirsisalistofdirectorieswithinthesearchdirectoryanditssubdirectories,andfilesisalistofallthefileswithinthesearchdirectoryanditssubdirectories.

TheifstatementisasimplewaytocheckwhetherafileisanMP3filebasedsolelyonitsfileextension.Ifithasthe.mp3extension,itisaddedtothemp3_fileslist,whichisthenpassedtotheplaylistcode.

GettinginputfromacommandlineInordertosetvarioussettingsforourplayerscript,forexample,thedirectoryinwhichyoucansearchforfiles,weneedawaytogetinputfromtheuserviaacommandline,andinthiscase,fromtheargumentspassedtothescriptwhenitisstarted.Todothis,wewillusetheargparsePythonmodule:

parser=argparse.ArgumentParser(description='BroadcastasetofMP3sover

FM')

parser.add_argument(

'-f','--frequency',

default=101.1,

type=float,

help='Frequencyonwhichtobroadcast')

params=parser.parse_args()

TheargparsePythonmoduleallowsyoutodefineasetofargumentsthatcanbepassedtoaPythonprogram,itallowsyoutoparsetheargumentswhenthescriptisrun,anditautomaticallyallowsyoutogenerateahelppage(accessedbypassing-htothescript).

Inthiscase,wewilladdanargumentforthebroadcastfrequency,whichissetusingeither-for--frequency;typeisusedtovalidateinputfromtheuser,defaultiswhatisreadbytheprogramiftheuserdoesnotsetavalue,andhelpiswhatisshownforthisargumentonthehelppage.

QueuingthemediafilestobeplayedOurmediaplayerwillalsoneedawaytomanagewhichfileshouldbeplayednext.Wewillimplementthisintwoways:linearplaybackintheorderthefileswerediscoveredandrandomizedplayback:

file_number=-1

whileTrue:

ifparams.random:

file_number=random.randint(0,len(filenames)-1)

else:

file_number+=1

iffile_number>=len(filenames):

return

play_file(filenames[file_number],params.frequency)

Here,ifthe--randomparameterhasbeenpassedtoourscript,wheneverweareabouttoplayafile,thefiletobeplayedwillbeselectedatrandomusingtherandintfunctionintherandomPythonmodule.Thisnumberisthenusedtogetacertainfilefromthelistoffilenamesthatwerepreviouslydiscovered.

UsingthemediaplayerscriptTheplayer.pyscriptcanbeinvokedusingthefollowingcommand:

pythonplayer.py-dmusic-f99.9--random

ThiswillsearchforallMP3filesunderthemusicdirectoryandbroadcastthemat99.9MHzinarandomorder.Afulllistofcommandswillbeavailabletoyouifyourun:

pythonplayer.py-h

SincetheradioisnotmuchofusewhenyouhavetoSSHintoittostartplayingthemusic,wewilladdacronjobthatwillstarttheplayer.pyscriptwhenthePibootsup.

Todothis,wewilluseashellscripttostartthePythonscript(start_player.sh):

#!/bin/bash

sleep20

cd/home/pi

pythonplayer.py-dmusic--random-f99.9&

Thiswillensurethattheplayerscriptisexecutedinthecorrectfolder,inthiscase,/home/pi,asthisiswhereourPiFMexecutablesandmusicdirectoriesare.

Next,wewilladdanentryinthecrontab,whichiswherecronjobsaredefined.Thiscanbeeditedwiththefollowingcommand:

sudocrontab-e

Thiscommandwillopenthedefaultcommand-linetexteditonthePi,nano,whichwillallowyoutoaddentriestothecrontab.Tostartourmediaplayerscript,wewillneedtoaddthefollowinglinetotheendofthecrontabthatisopened:

@reboot/home/pi/start_player.sh

Inourcase,wewillusethe@rebootcronruleinsteadofspecifyingatimeforthecommandtoberun,andasthenamesuggests,thiswillrunthegivencommandwhentheOSstarts.

PressCtrl+XfollowedbyYandEntertosavethechangestothecrontab,thenusethefollowingcommandtorebootthePi,andifallgoesasplanned,startyourpersonalizedradiostation:

sudoreboot

SummaryInthischapter,wecoveredthebasicsetupofthePihardwareandRaspbianOS.YoulearnedhowtodiscovertheIPaddressofthePiinordertoallowremoteaccesstoitoverSSH;thisprocesswillbeusedinthemajorityoftheprojectslaterinthisbook.

WealsotookaquicklookattheGPIOexpansionheader,andhowitistypicallyusedtointerfacewithexternalhardware.WealsousedthisasacrudeFMtransmitterthroughwhichwewroteasinglePythonscripttobroadcastmusic.

Inthenextchapter,wewillgointofurtherdetailsregardinghowtosetupvarioussoftwarepackagesinordertorunthemonthePi,aswellasyouwilllearnthevariouswaystoconfigurenetworkingwhenwemakeaportablespeakersystemthatrunstheLogitechMediaServer.

Chapter2.PortableSpeakerSystemInthischapter,wewillbuildawireless,battery-poweredspeakersystemthatcanbecontrolledusingawebbrowserorsmartphone.

Toprovidethemusicforthespeakersystem,wewillusetheLogitechMediaServersoftware,whichisapieceofsoftwarethatcanbeusedtostreammusic,videos,andphotosfromonecomputeronanetworktomultipleotherdevices.Italsoallowsustocontroltheplaybackfromanycomputerorsmartphoneonthesamenetwork.

Initially,wewillsetupthePitoconnectittoanexistingserver(theonerunningonalaptopforinstance),whichissuitableforusearoundyourhomeorgarden.Later,wewilllookathowtomakethesystemtrulyportablebyremovingtheneedforanexistingserverandnetwork.

ThesystemwillbeselfcontainedwithinastandardflightcasewiththespeakersexposedwhenthelidisopenedasitispossibletorunLogitechMediaServeronthePiitself.Itisnotnecessarythatyouhaveanycontrolsonthesystemitselfotherthanapowerswitch.

ThisprojectisbasedonasimilarprojectmadebyIainYarnallatMakerSpace,Newcastle.

WhatyouwillneedThisisalistofthepartsthatyouwillneedforthisproject;specificpartshavealinkofwheretheycanbepurchased(itisrecommendedthatyouusethesespecificpartsasothersimilarpartsmayneedanassemblythatdiffersfromtheinstructionsgivenhere),andallotherpartscanbepurchasedfromanelectronicscomponentsstore:

TheRaspberryPiAUSBstoragedevicetostoreamedialibrary(itispossibletouseaharddrive;however,tokeepthewiringsimple,itisadvisablethatyouuseamemorystick)AWi-Fiadapter(uk.rs-online.com/web/p/product/7603621/)Aflightcase(http://www.maplin.co.uk/p/flight-case-triple-pack-with-dividers-n50ju)Alengthof26AWGwireAlengthof32AWGwireA3.5mmstereoaudioconnectorAstripofterminalblocksAfuseholderand1AmpfuseEight20mmM3screws,washers,andnutsTwofull-rangespeakers(http://cpc.farnell.com/visaton/2133/speaker-full-range-5-60w-black/dp/LS02184)Twomonoamplifiermodules(http://cpc.farnell.com/1/1/85173-amplifier-module-18w-m033n-kemo-electronic.html)Avariableswitchmodevoltageregulator(http://imall.iteadstudio.com/im130731002.html)Apowerswitch(http://cpc.farnell.com/arcolectric-switches/c1300abaaa/switch-spst-16a-250vac-black-i/dp/SW05094)Volumecontrol(stereopotentiometer)(http://cpc.farnell.com/_/lp-200-8/speaker-l-pad-stereo/dp/LS00544)Abattery(http://www.hobbyking.com/hobbyking/store/__11945__Turnigy_nano_tech_2200mah_4S_35_70C_Lipo_Pack.html

ToolsyouwillneedThisisalistoftoolsthatyouwillneedforthischapter;theycanallbepurchasedfromeitheranelectronicscomponentsstoreoratool/hardwarestore:

Drillanddrillbitsrangingfrom3mmto10mmAjigsawAtrysquare(optional)AsolderingironandsolderAmultimeterAsmall,flatscrewdriverAsmallPosidrivescrewdriver

SettingupLogitechMediaServerWewillfirststartbydownloadingandinstallingLogitechMediaServer,whichistheserverbackendthatmanagesthemedialibraryandcontrolstheplayersbasedonthecommandsfromdevicesthatcancontroltheserver(knownascontrollers).Examplesofcontrollersincludethewebinterfaceandsmartphoneapplications.

Theplayersaredevicesthatactuallyoutputaudio(alsoknownasSqueezeboxclients),ourPi,forexample.Itispossibletohaveseveralcontrollersandplayersrunningfromthesameserver.

Togetstarted,gotohttp://www.mysqueezebox.com/download,anddownloadthecorrectversionforyourOS.Inmostofthecases,thedownloadisanexecutableorapackagefilethatcanbeinstalledinthesamewayasanyotherpieceofsoftware.

OnceLogitechMediaServerisinstalled,openawebbrowseronthesamePCandnavigatetolocalhost:9000;youshouldseetheLogitechMediaServerwebinterface,asshowninthefollowingscreenshot.Thisallowsyoutobrowsethemedialibraryandstreammediatoplayersconnectedtothatserver.

InordertomakeyourmediaavailableinLogitechMediaServer,youmayneedtochangethesearchpathandperformalibraryrescan;thiscanbedonebyclickingontheSettingslinkinthebottom-rightcorneroftheBasicSettingspage:

Next,selectBrowseonthefolderthathasMusicticked;thiswillopenadirectorytreethatwillallowyoutobrowsethedirectoryyourmusicisstoredin.Onceyoudothis,clickonClose,andunderRescanMediaLibrary,clickonRescan.Thiswilllookintheconfigureddirectoriesformediafilesandaddthemtothelibrary,whichmaytakeafewminutesdependingonthesizeofyourmediacollection;theprogressofthisprocesscanbeviewedintheInformationtab.ClickonApplyinthebottom-rightcornerofthescreentoreturntothelibraryview.

Oncebacktothelibraryview,youmayhavetorefreshthepageinordertodisplayyournewmedia;thiscanbedonebyclickingontheLogitechMediaServertextinthetop-leftcornerofthepage.

SincethisisallLogitechMediaServercanwithoutaplayer,wewillnowsetupthePiasaSqueezeboxclient.

SettingupthePiasaSqueezeboxclientInordertousethePiasaSqueezeboxclient,wewillusetheopensourcesoftware,squeezelite(https://code.google.com/p/squeezelite).

First,weneedtoinstallsomeprerequisitesonthePiwhicharerequiredtorunthesqueezelitesoftware,whichcanbedoneusingthefollowingcommand:

sudoapt-getinstall-ylibflac-devlibfaad2libmad0

Next,wewilldownloadtheprecompiledsqueezelitebinaryfromtheGoogleCodepageusingwget.Wewillgiveitexecutepermissionstoitandmoveitintothebinarydirectory,allowingittobeexecutedlikeanyothercommand-lineapplication:

wgethttp://squeezelite-downloads.googlecode.com/git/squeezelite-armv6hf

sudochmoda+xsqueezelite-armv6hf

sudomvsqueezelite-armv6hf/usr/bin

Nowthattheclientapplicationisinstalled,wewilldoalittlebitoftestingtobesurethatthesetupisworkingproperly.Wewilldothistodeterminetheparametersthatneedtobepassedtotheclienttogetthebestaudioqualityandperformance.

Tostart,executethefollowingcommand:

squeezelite-armv6hf-nPi-a160

Thiscommandwillstartsqueezeliteinanauto-discoverymodeinwhichitwillsearchthenetworkforaLogitechMediaServerinstanceandconnecttothefirstoneitfinds.Ifyouhavemorethanoneinstanceandwanttospecifytheservertoconnectto,thenyoucanusethe-sparameter:

squeezelite-armv6hf-sserver_ip:port-nPi-a160

The-nparameterdefinesthenameoftheclientandsubsequently,whatitwillbecalledinLogitechMediaServer;thisisusefulforidentificationwhenyouareusingmorethanoneclientonthesameserver.The-aparameterisusedtospecifyadditionalALSAparametersthataretobeusedwhileopeningtheoutputaudiodevice;inthiscase,wewillincreasethedefaultbuffersize,whichwillhelpustorectifysomeaudioqualityissuesthatmayoccurwiththePi.

OncesqueezeliteisrunningonthePi,gobacktotheLogitechMediaServerwebinterfaceandselecttheplayerfromthedrop-downlistinthetop-rightcornerofthepage(youmayneedtorefreshthepagetodisplaytheplayer).

YoucanthenbrowseyourmedialibraryandqueuethemusictobeplayedonthePiusingtheaddandplaybuttons,whichcanbeseenwheneachmediaitemishighlighted,asshowninthefollowingscreenshot:

SettingupWi-FionthePiRunninganEthernetcablethroughthePiisalittlebitunrealisticforthisuse.Hence,wewillconnectthePitoawirelessnetwork.SincenotallWi-FiadaptersworkwellwiththePi,itisagoodideatocheckthelistofthesupporteddevices(http://elinux.org/RPi_USB_Wi-Fi_Adapters)beforepurchasingonespecificallyforthisproject.

Firstly,wewillmakesurethatwehavealltheWi-Fitoolsinstalledusingthefollowingcommand:

sudoapt-getinstallwpasupplicantwireless-tools

ThereisagoodchancethatthesepackageswillalreadybeinstalledonRaspbian,butitisasimplesteptocheckbeforehand.

Itislikelythatyoualreadyknowtheservicesetidentifier(SSID)ornameofthewirelessnetworkyouwanttoconnectto,butifnot,orjusttocheckwhetheritisbeingpickedupbytheWi-Fiadapter,usethefollowingcommandtogetalistofalltheWi-Finetworksavailableintherange:

sudoiwlistwlan0scan|grepESSID

Youwillgetoutputsimilartothefollowing:

Nowthatweknowthenameofthenetworkwewanttoconnectto,wecangoaheadandaddanentryinthewpa_supplicantconfigurationfile,whichcontainstheconnectiondetailsforthenetwork.Thiscanbeeditedbythenanotexteditor,usingthefollowingcommand:

sudonano/etc/wpa_supplicant/wpa_supplicant.conf

Attheendofthefile,addthefollowinglinesandreplaceSSIDandPASSWORDwithSSIDandthepasswordforyourwirelessnetwork:

network={

ssid="SSID"

psk="PASSWORD"

key_mgmt=WPA-PSK

}

Oncethelineshavebeenaddedtothefile,savethechanges,exitnano,andrebootthePiusingthefollowingcommand:

sudoreboot

OncethePihasbooted,SSHbackintoitandmakesurethatthePihasaWi-Ficonnection,usingthefollowingcommand:

ifconfig

Iftheconfigurationissuccessful,youwillseeoutputsimilartothis,whichshowsanactiveEthernet(on192.168.0.2)andaWi-Fi(on192.168.0.18)connection:

Afterthis,youshouldbeabletoSSHinthePiviaitsWi-FiIPaddressanddisconnecttheEthernetcable.

RunningsqueezeliteasadaemonSincewewantthePitobereadytostreammusicwithouthavingtodoanythingotherthanapplypowertoit,weneedawaytolaunchsqueezelitewhenthePiboots;thistime,wewilllookatanotherwayofdoingthis,usingadaemon.

Adaemonisaprogramthatrunsinthebackgroundandisnotdirectlyvisibletotheuser;becauseofthis,itisoftenusedforapplicationssuchasservers.

Inourcase,wewillusethestart-stop-daemonutilitytocreateadaemonthatwillstartsqueezeliteonboot.Wewilldothisbywritingashellscriptandplacingitinthe/etc/inti.ddirectory:

#!/bin/bash

###BEGININITINFO

#Provides:squeezelite

#Required-Start:

#Required-Stop:

#Default-Start:2345

#Default-Stop:016

#Short-Description:Squeezeliteclient

#Description:Logitechmediaserverclient

###ENDINITINFO

DAEMON_USER=pi

PIDFILE=/var/run/squeezelite.pid

DAEMON=/usr/bin/squeezelite-armv6hf

DAEMON_OPTS="-nPi-a160"

do_start()

{

start-stop-daemon--start--background--pidfile$PIDFILE--make-pidfile

--user$DAEMON_USER--chuid$DAEMON_USER--startas$DAEMON—$DAEMON_OPTS

}

do_stop()

{

start-stop-daemon--stop--pidfile$PIDFILE--retry10

}

case$1in

start)

do_start

;;

stop)

do_stop

;;

restart)

do_stop

do_start

;;

*)

;;

esac

Makethescriptexecutableandmoveittothe/etc/init/ddirectory:

sudochmoda+xsqueezelite

sudomvsqueezelite/etc/init.d/squeezelite

Finally,usethefollowingcommandtoupdatethelistofdaemons:

sudoupdate-rc.dsqueezelitedefaults

Toensurethatthedaemonisworkingproperly,trytostartsqueezelitebyexecuting:

sudoservicesqueezelitestart

Checkwhethertheprocessisrunning:

psaux|grepsqueeze

Thisshouldgiveyououtputsimilartothefollowing:

Theprecedingoutputshowsthatthesqueezeliteprocessisrunning;thiscanalsobeverifiedifyouattempttostreammusicintheplayer.

BuildingtheelectronicsTheelectronicsforthespeakersystemcanbesplitintotwomainsections—thepowercircuitandtheaudiocircuit.

Thecircuitstructureoftheelectronicsisshowninthefollowingdiagram:

Thespeakersystemblockdiagram

Notethecolorcodingofthewiring.Here,blackshowsthepowerground,grayshowstheaudioground,cyanshowstheunamplifiedaudio,blueshowstheamplifiedaudio,yellowrepresentsthebatteryvoltage,andredshows5V.

Notethecolorcodingofthewiring.Thisisimportantasitisthemostcommonwayinwhichdifferentsignalsandpowersuppliesareidentifiedwithinanelectronicproduct.Thereareafewcommonconventionsthat,whilearenotusedhere,aregoodtoknow;blackisalwaysground,redandyellowusuallyindicateapowersupply(5Vand12V,respectively),andyellowandgreenstripesusuallyrepresentamainsearth.

Forsmallprojects,suchasthis,followingastandardcolorcodeforwiringisnotasimportant.Differentsignalshaveacoloredwireoftheirowntomakeidentificationandtroubleshootingeasier.

NoteUnlessotherwisestated,a26AWGwireshouldbeused.Thewirecoloryouchoosetousedoesnothavetomatchtheonesshownintheprecedingdiagrams;however,itispreferablethatyoufollowittomakeidentificationeasier.

TheamplifiercircuitFirstly,wewillwirethetwomonoamplifiermodulestoastripofterminalblockstomakeastereoamplifiermodule.Thisisdonebyconnectingthecommonconnectionsfromeachamplifiertogetherandkeepingthesignalandoutputconnectionsseparate,asshowninthefollowingdiagram:

Next,takethevolumecontrolandsolderthewiresontoitintheconfiguration,asshowninthefollowingdiagram:

Theaudioinputwiresshouldberelativelyshort(around50mm)andconnectedtoastripofthreeterminalblocks;theoutputshouldhaveenoughwiretoreachtheamplifiermodule(around150-200mm).Thisvolumecontrolisessentiallycomprisedoftwopotentialdividerswiththeirwipersfixedtogethersuchthateachpotentialdividerisalwaysatthesameposition.

Now,wecansolderwirestothe3.5mmaudiojack;sincethisisabitsmalleranditwillonlycarrytheunamplifiedaudiosignal,wecanusea32AWGwireforthis:

Theaudioconnectorcannowbeconnectedtotheterminalblockonthevolumecontrol;atthisstage,theorientationoftheleftandrightchannelsisnotimportant.

Then,connecttheoutputfromthevolumecontroltothefirstthreeconnectionsontheamplifierterminalblocks;again,theorientationisnotimportantatthisstage.

Sincethepowergroundconnectionontheamplifierwillhavetobeconnectedtoboththespeakers,thebatteryandtheDC-DCconvertertopowerthePiwillbebesttoextendthespeakersconnectionstotheirownstripofterminalblocks.Thiswillreducethenumberofconnectsthathavetobemadeinthesameconnection.

Thisissimplyacaseofaddingashortlengthofwire(around50-100mm)tothetwospeakeroutputsandpowergroundfromtheamplifierterminalblocksandconnectingthemtoastripofthreeterminalblocks:

Next,weneedtosolderawire(around300mm)tothetwospeakers.Notethatthespeakerwillhavemarkingsthatshowthecorrectpolarityitistobewiredin:

Now,connecteachspeakertothestripofthreeterminalblockscomingfromtheamplifiermodules.Onceagain,thecorrectspeakerorientationisnotimportantatthisstage.

Thisisallwithrespecttothewiringfortheaudiosectionofthespeakersystem.

RunningthespeakersystemonbatterypowerSincethebatterywewilluseisratedat14.4V,weareabletopowertheamplifierdirectlyfromthebattery.However,thePimustbepoweredwith5V.So,wewillneedapowerconvertertobeabletopowerthePiusingthebattery.

ThepowerconverterwewilluseisaDC-DCswitchmodeconverter,whichwillacceptinputvoltagefromthesetoutputvoltageupto35V.Therefore,wewillcontinuetopowerthePiasthebatteryvoltagedropswhileunderheavierload(forexample,whenplayingathighervolumes)orasthebatterystartstodrain.

Aslithiumpolymerbatteriescanbeverydangerousifusedincorrectly,itisvitalthatafuseisusedinlinewiththepowerswitchtoprotectthebatteryjustincasethere’safaultinthespeakersystem.Aratingofaround0.8to1.5Awillbesuitableforthispurpose.

Wewillstartwithpoweringjusttheamplifiers.Thisisafairlysimpletaskasallitinvolvesisconnectingthebatterypositiveterminaltothepowerconnectorontheamplifierterminalblocksviatheswitchandfuse.Thegroundisconnecteddirectly,asshownintheearlierdiagram.Performthefollowingstepstoconnectthecircuit:

1. Taketheconnectorforyourbattery,andassumingthatithasleadspresolderedontoit,connectthemtoastripoftwoterminalblocks.Iftheydonothaveleadssolderedontothem,thenthisshouldbedonefirstusingashortlengthofwire(around50mm).

2. Soldera100mmlengthofwireontoonepoleofthepowerswitchandconnecttheotherendtothepositiveterminalonthebatteryterminalblock.

3. Soldera50mmlengthofwirefromtheotherswitchpoletoonecontactofthefuse.4. Soldera50mmlengthofwirefromtheotherfusecontactandconnecttheotherend

tothepositivepowerconnectionontheamplifierterminalblocks.5. Connectthegroundsofthebatteryterminalblockandtheamplifierterminalblocks

witha100mmlengthofwire.

Oncethesestepshavebeencompleted,thesetupshouldlooklikewhatisshowninthefollowingimage:

Nowwouldbeagoodtimetogivetheaudioelectronicsatestbyconnectingthebatteryandpoweringontheamplifiers.YoucaneitherusethePipoweredfromaUSBoranyothermediaplayerastheaudiosource.Itisbesttohavethevolumecontrolsettoitslowestsettingandgraduallyincreaseit.

Next,wewanttopowerthePifromthebatteryusingtheDC-DCconverter.Therearetwomainwaysofdoingthis:eitherbyapplyingpowertotheGPIOheaderorbyback-poweringthePiusingapoweredUSBhub.Inthiscase,IwillbepoweringviatheGPIOheader,whichwilllikelybesufficientforwhatwearedoinghere.PoweringusingapoweredUSBhubwillonlybeneededifyouareusinganexternalharddrivetostorethemusiclibrary.

First,weneedtosolderwirestoeachoftheterminalsoftheDC-DCconverterandnotethepolarityoftheconnectionstoensurethatthecolorcodingofthewiringisconsistent.Alengthofaround100mmissufficientforeachconnection.

Next,connectthepositiveandgroundconnectionsonthepowerinputsideoftheconvertertothepositiveandgroundconnectionsontheamplifierterminalblocks,andconnectthetwoleadsfromtheoutputterminalsoftheDC-DCconvertertoastripoftwoterminalblocks.

NowthatwehavetheDC-DCconverterconnected,weneedtosetittothecorrectoutputvoltagebeforeweconnectittothePi.Todothis,setamultimetertothevoltagemodeandplacetheprobesacrossthetwoconnectionsontheterminalblocksconnectedtotheDC-DCconverter’soutput(ifpossible,screwthetipsoftheprobesintotheterminalblockstoavoidhavingtoholdtheminplace).Turnthepoweron,andifneeded,adjusttherangeonthemultimeter.

Usually,Ifindthattheseconverterscomepresettotheoutputjustbelowtheinputvoltage,

whichwouldbefartoohighforthePi,whichisdesignedtooperateat5V.Inordertoadjustthevoltage,useasmall,flat-headscrewdrivertoadjustthesquarebluepotentiometer.Thisisamultipleturnpotentiometer,sodonotbesurprisedifittakesafewrotationsofthepotentiometerforthevoltagetochange.Areasonablevoltagetoaimforis5.1V,asunderload,thevoltageisexpectedtodropslightly.

Oncethevoltageiscorrected,turnthepoweroff,removethemultimeterfromtheoutputoftheDC-DCconverter,removeoneendoftwo0.1inchjumperleads,andconnectthemtotheterminalblockontheoutputoftheDC-DCconverter.Connectthepositiveleadtopin4oftheGPIOheadersonthePiandthegroundleadtopin6.

Bynow,thesetupshouldlooksimilartothefollowing:

Oncethisisdone,applypoweroncemoreandwithinafewseconds,thePishouldstartbootingup.Ifitdoesnot,turnthepoweroffimmediatelytopreventpossibledamagetothePiandbattery,anddouble-checkallofthewiringagainsttheblockdiagramshownearlierinthechapter.

BuildingtheenclosureforthespeakersystemSinceweareusingapremadeflightcaseasthebaseforourspeakersystem’senclosure,allwehavetodoiscutasinglepanelthatwillholdthespeakers,volumecontrol,andpowerswitchonapanelthatisexposed.Wecandothisbyopeningthecase,thushidingthePi,battery,andelectronicsbehindit.

Tomakethispanel,wewillusea3mmmediumdensityfiberboard(MDF);thisisacheapmaterialandisveryeasytoworkwith.

First,wewillneedtocutasquareofMDFthatisjustsmallerthantheopeningintheflightcase.Todothis,firstmeasurethelengthandwidthoftheinsideoftheflightcaseandmarkthisdistanceawayfromtwoedgesofasheetofMDF,asshowninthefollowingimage:

Next,takeatrysquareanddrawalineparalleltoeachedgeinlinewiththemarkingsinordertogiveanoutlineofwherethesquareneedstobecuttogetourpanelasshowninthefollowingfigure.

NoteWhenusingpowertools,propersafetyprecautionsshouldbeundertaken.Eyeprotectionshouldalwaysbewornandmains-poweredtoolsshouldbeprotectedusingaresidualcurrentdevice(RCD).

Oncethisisdone,wecantakeajigsawandcutalongthelinestogetthepanel,whichshouldbeabletosnuglyfitintheopeningoftheflightcase.

Nowthatwehavethebasicpanelfortheenclosure,wewillcutthetwospeakerholes.Sincedifferentspeakersaremountedindifferentways,Iassumethatyouareusingthesamespeakersthatarelistedonthepartslisthere.

Mountingthespeakerswillfirstinvolvecuttingalargeholeintothesheettosetthespeakersinandthendrillingfoursmallerholesthatareusedtoboltthespeakertothepanel.Fortunately,forthespeakers,thelargeholecanbemarkedouteasilybytracingaroundaCD.

Onceyouhavetheoutlineofthespeakerpositionedcorrectly,drilla10mmholeneartheedgeofeachcircle,asshowninthefollowingimage.Thiswillallowustogetinsidethecirclewiththejigsawinordertocutalargeholeinthepanel.

Oncethisisdone,insertthebladeofthejigsawintotheholeandcutaroundtheoutlineofthecircleforeachspeaker.Itisn’tvitalthattheholesarecutneatlyoraccurately,sincethespeakerwillcoverthisedgewheninstalled;however,itisimportantthatthespeakersitsflatwhenitismountedonthecutout.

Next,weneedtodrillthemountingholesthatwillbeusedtoboltthespeakerstotheMDFpanel;inthiscase,wewilldrill4mmholesanduseM3screwsandnutstomountthespeakers.

First,markthepositionsofeachholebyplacingthespeakerintotheholeandmakingamarkontheMDFthroughtheholeinthespeakerfascia(withapencil,forexample).

Next,drilla4mmholeineachmarkedposition.Itwouldbeagoodideatocheckwhethertheholeslineupwiththespeakercorrectlybytrialfittingitwithjustthescrews;however,wewillmountthespeakersproperlylater.

Next,weneedtodrillasingleholelargeenoughfortheshaftofthevolumecontrol.Thebestplacetopositionthisisinbetweenthespeakers,butfarawayenoughtoleaveroomforthefrontplate.Oncethepositionismarkedout,drilltheholeandremoveanyloosepiecesofmaterial.

Theholeforthepowerswitchisprobablythemostdifficultsinceitisasquarehole.Forthis,wewilldrilltwo10mmholesandusethejigsawtomakethetwoendssquareandremovethematerialinbetweenthem.

Thetwoholesshouldbearound15-20mmapart.Thisshouldallowasnugfitoftheswitchoncethefullholehasbeencutoutusingthejigsaw.Inthiscase,sincetheedgeofthecutmaybemorevisible,itisagoodideatotakeasmallamountofmaterialoffineachpassandtokeepcheckingwhethertheswitchfitsneatly.

Nowthatallthemountingholeshavebeencutoutofthepanel,itistimetomounteachcomponentonthepanel.Wewillstartwiththetwospeakers,whichcanbemountedbyinsertingthespeakerintothelargeholeandfasteningitinplaceusinganM3machinescrewineachmountingholewithacorrespondingwasherandnut.Tomakethewiringneater,itisagoodideatohavetheterminalsofeachspeakerfacingthesamedirection.Irecommendhavingthemfacethebackoftheflightcase.

Next,thepowerswitchcanbefitted;thisrequiresyoutodisconnecttheconnectionstotheamplifierterminalblocksfirst.Oncedisconnected,thisissimplyacaseoffeedingthewiringandfuseholderthroughthemountingholeandpushingtheswitchintothehole.Onceinplace,itshouldbekeptsecurelyinplacebyfrictionalone.

Next,thevolumecontrolcanbemountedbypushingthethreadedshaftthroughtheholedrilledforitfromthebackoftheMDFpanel.PlacetheplasticfrontplateovertheshaftonthefrontoftheMDFpanelandfastenitinplaceusingtheincludednuts.Theknobshouldthenbepushedon,ensuringthattheindicatorlinesupwiththeminimumindicatorontheplasticfrontpanel.

Bythistime,thefrontoftheMDFpanelshouldlooksimilartothefollowingimage:

AllthatislefttodonowismounttheDC-DCconverterandamplifierstothebackofthepanel,reconnect,andtidyupthewiring.

Sincetheamplifiermoduleshavemountingholes,Iusedthesetothreadsomelargecabletiesthroughandfastenedthemtothetwospeakers.ThisallowsasecuremountingoftheamplifiersthatdoesnotneedadditionalholestobedrilledintheMDFpanel.

TheDC-DCconvertercanbemountedanywhereontheMDFpanelusinganysuitableadhesive.Iwouldrecommendhotglueasitallowsfairlyeasyremovalwithoutriskingdamagetotheconverter,butyoucanalsousedouble-sidedtape.

Thenextstepistoreconnectallthewiringthatiscurrentlydisconnected.Whiledoingso,itisagoodideatotrimanywiresthatareexcessivelylongsothateachwireisjustlongenoughtoreachwhereitshouldconnectto.Thisismainlydonejusttomakethewiringtidier.

Bynow,thebackshouldlookasshowninthefollowingimage:

AssumingthatyouareusingthesameflightcasethatIused,therearetwodividersincludedthatmakeaperfectspacertokeeptheMDFpanelagooddistancefromthebottomoftheflightcase,thespacersshouldbeplacedaround40mmfromeachsideofthecase.

AllthatislefttodonowisreconnectthePiandbatteryandgivethesystematest.

RunningLogitechMediaServeronthePiOurcurrentsolutionisallwellandgoodifyouonlywanttousethesystemaroundthehomeandgarden.However,tomakethesystemtrulyportable,weneedtomovethemediacollection,LogitechMediaServer,andwirelessnetworktothePi.

CreatingabackupimageofanSDcardSincewewillnowbemakingafewchangestothesoftwarerunningonthePi,itmaybeworthwhilethatyoutakeanimageoftheSDcardsothatlater,itiseasytorestorethePitoitsworkingstate.

Fortunately,thisisaverysimplethingtodo,andsinceitisessentiallyjustthereverseofwritingtheOSimagetothecard,itcanbedonewiththeddutility:

sudoddif=/dev/sdbof=working.img

ThiswillcreateanimageoftheSDcardat/dev/sdbandsaveittotheworking.imgfile.ThiscanlaterberewrittentotheSDcardinthesamewayasafreshOSimage.

OnethingworthnotingaboutthismethodisthatitwilltakeanimageoftheentireSDcard,includinganyfreespace.Hence,thesizeoftheimageisequal(ormarginallysmallerinthemajorityofcases)tothecapacityoftheSDcard.Thismeansthattorestoretheimage,youneedanSDcardofatleastthecapacityofthecardtheimagewastakenfrom.Forthisreason,itisgoodtotryanduseanSDcardthatisjustbigenoughforwhatyouneed,inordertobothrestoretheimageontoalargerrangeofSDcardsandtoreducetheamountofstoragerequiredtokeeptheimages.

AutomountingaUSBstoragedeviceSinceitslikelythatyourmediacollectionmaynotentirelyfitonasingleSDcard(aswellasRaspbian),wewillopttostorethisonanexternalUSBdevice,thiscouldeitherbeaUSBmemorystickoranexternalharddrive.Theprocessofdoingthisisthesameforallstoragedevices.

First,weneedtoknowthepathtothestoragedeviceandthefilesystemituses.Bothcanbeobtainedusingthefollowingcommand:

sudoblkid

Thiswillgiveoutputsimilartothefollowing.Here,youcanseethetwopartitionsontheSDcard(mmcblk0p1andmmcblk0p2)aswellasaUSBmemorystick(/dev/sda1).Ensuringthatyouassignalabeltothepartitionwhileformattingitwillhelptomakeidentificationeasier:

/dev/mmcblk0p1:SEC_TYPE="msdos"LABEL="boot"UUID="787C-2FD4"TYPE="vfat"

/dev/mmcblk0p2:UUID="3d81d9e2-7d1b-4015-8c2c-29ec0875f762"TYPE="ext4"

/dev/sda1:SEC_TYPE="msdos"LABEL="DANNIXON"UUID="321A-15D0"TYPE="vfat"

NotethepathtothedeviceattheverystartofthelineandthepartitiontypegivenbyTYPE.Wewillneedbothofthesepiecesofinformationwhenwesetupthepartitiontobemountedattheboottime.

Next,wewillcreateadirectoryforthepartitiontobemountedon.Thisisthepaththatwillbeusedtoaccesstherootofthepartitionwhenitismounted.Inthiscase,wewillcreateadirectoryunder/media.InLinuxthisisthedirectoryusedformountingremovablefilesystems;thenameofthedirectoryisnotcritical,butsomethingdescriptiveisrecommended:

sudomkdir/media/music

Nowthatthemountpointhasbeencreated,wewillmodifythefilesystemtable(fstab)toautomaticallymountthedrivewhenthePiboots;thiscanbedoneusingthenanotexteditor.Thefilesystemtableneedstobemodifiedasroot:

sudonano/etc/fstab

ToaddthepartitionofourUSBdevice,thefollowinglineshouldbeaddedtotheendofthefile,replacing/dev/sda1withthepathtoyourpartitionandvfatwiththepartitiontype(whichwerediscoveredearlier):

/dev/sda1/media/musicvfatdefaults00

Oncefinished,pressCtrl+Xtosaveandexit.RebootthePiusing:

sudoreboot

OncethePihasbooted,checkwhetherthepartitionhasbeenmountedandisaccessibleusing:

ls/media/music

ThisshouldshowyouthefilesanddirectoriesattherootofthepartitionontheUSBstoragedevice.

InstallingLogitechMediaServerNowthatwehavethemusiccollectionstoredlocallywiththePi,weneedtomoveourLogitechMediaServerinstancethere.Officially,thereisnosupportforLMSonthePi,however,AllThingsPi(http://allthingspi.webspace.virginmedia.com/)hasalreadydonetheworkofportingLMStorunonthePi.

Firstly,thereareafewmorelibrariesthatarerequiredbyLogitechMediaServerthatmayneedtobeinstalledfirst.Thiscanbedonewiththefollowingcommand:

sudoapt-getinstalllibjpeg8libpng12-0libgif4libexif12libswscale2

libavcodec53

Now,wecandownloadandinstalltheDebianversionofLogitechMediaServerfromtheLogitechwebsite:

wget

http://downloads.slimdevices.com/LogitechMediaServer_v7.7.2/logitechmediase

rver_7.7.2_all.deb

sudodpkg-ilogitechmediaserver_7.7.2_all.deb

Asitis,theinstallationneedssomemodificationsbeforeitcanbeusedonthePi.Beforewestartwiththis,weneedtoensurethatLMSisnotalreadyrunning;thisisdonebyattemptingtostoptheservice:

sudoservicelogitechmediaserverstop

Next,weneedtodownloadandextracttherequiredfilesthatwillbeusedtomodifytheLMSinstallationfromAllThingsPi:

wgethttp://allthingspi.webspace.virginmedia.com/files/lms-rpi-

raspbian.tar.gz

tar-zxvflms-rpi-raspbian.tar.gz

Now,wecanperformtherequiredmodificationsusingthefollowingcommands:

sudopatch/usr/share/perl5/Slim/bootstrap.pmlms-rpi-bootstrap.patch

sudomvarm-linux-gnueabihf-thread-multi-64int

/usr/share/squeezeboxserver/CPAN/arch/5.14/

sudomvlibmediascan.so.0.0.0libfaad.so.2.0.0/usr/local/lib

sudomv/usr/share/squeezeboxserver/Bin/arm-linux/faad

/usr/share/squeezeboxserver/Bin/arm-linux/faad.old

sudomvfaad/usr/share/squeezeboxserver/Bin/arm-linux

sudoln-s/usr/local/lib/libmediascan.so.0.0.0

/usr/local/lib/libmediascan.so

sudoln-s/usr/local/lib/libmediascan.so.0.0.0

/usr/local/lib/libmediascan.so.0

sudoln-s/usr/local/lib/libfaad.so.2.0.0/usr/local/lib/libfaad.so

sudoln-s/usr/local/lib/libfaad.so.2.0.0/usr/local/lib/libfaad.so.2

sudoldconfig

sudochown-Rsqueezeboxserver:nogroup/usr/share/squeezeboxserver/

Oncewearefinished,LogitechMediaServershouldbereadytouse.However,IhadtorebootbeforeIwasabletonavigatetothewebinterface:

sudoreboot

OncethePihasbooted,navigatetoPI_IP:9000(wherePI_IPistheIPaddressofyourPi)toaccesstheLMSwebinterface.Here,youcanfollowthesamestepsdescribedearliertosetupyourmedialibrary.KeepinmindthatthewebinterfaceandmediascanningmayseemslightlyslowerthanonastandardPC.ThisismainlyduetothelowersystemresourcesofthePi.

SettingupthePiasaWi-FiaccesspointSincewewanttobeabletousethespeakersystemwhereverwego,weneedawaytoconnecttothePiwithoutrelyingontheavailabilityofawirelessnetwork.TheeasiestwaytodothisistoturnthePiintoaWi-Fiaccesspointthatwecanconnecttousingasmartphone.

First,wewillassignastaticIPaddresstotheWi-Fiinterface.Startbyopeningtheinterfacesfileinnano:

sudonano/etc/network/interfaces

Editthefilesothataftertheallow-hotplugwlan0line,itlookslikethefollowingcode.Thiscodeistellingthewlan0interfacetotakeastaticIPaddressratherthanusingDHCPaswasdonepreviously:

allow-hotplugwlan0

ifacewlan0inetstatic

address192.168.42.1

netmask255.255.255.0

#ifacewlan0inetmanual

#wpa-roam/etc/wpa_supplicant/wpa_supplicant.conf

#ifacedefaultinetdhcp

Next,wewillsetuptheDHCPserver,whichwillprovideanIPaddresstoanydevicesthatconnecttotheWi-Finetwork:

sudoapt-getinstallisc-dhcp-server

sudonano/etc/dhcp/dhcpd.conf

ThiswillopennanotoedittheDHCPserverconfiguration.First,uncommenttheauthoritativeline.ThistellstheserverthatitisthemainDHCPserveronthenetwork.Next,commentoutthefollowingtwolines:

optiondomain-name"example.org";

optiondomain-name-serversns1.example.org,ns2.example.org;

Next,addthefollowinglinestotheendofthefile:

subnet192.168.42.0netmask255.255.255.0{

range192.168.42.10192.168.42.50;

optionbroadcast-address192.168.42.255;

optionrouters192.168.42.1;

default-lease-time600;

max-lease-time7200;

optiondomain-name"local";

optiondomain-name-servers8.8.8.8,8.8.4.4;

}

Then,weneedtotelltheDHCPserverwhichinterfacestouse.Thisisdonebyeditingthefollowingconfigurationfile:

sudonano/etc/default/isc-dhcp-server

Addwlan0tothelistofinterfacessothatthelinelookslikethis:

INTERFACES="wlan0"

Next,wewillinstallandconfiguretheaccesspointdaemon.Thisinvolvescreatingaconfigurationfilefortheaccesspoint:

sudoapt-getinstallhostapd

sudonano/etc/hostapd/hostapd.conf

Addthefollowinglinestotheconfigurationfile,replacingNETWORKandPASSWDwiththeSSIDandkeyyouwishtouseforthewirelessaccesspoint:

interface=wlan0

driver=nl80211

#driver=rtl871xdrv

ssid=NETWORK

hw_mode=g

channel=6

macaddr_acl=0

auth_algs=1

ignore_broadcast_ssid=0

wpa=2

wpa_passphrase=PASSWD

wpa_key_mgmt=WPA-PSK

wpa_pairwise=TKIP

rsn_pairwise=CCMP

Now,weneedtotellthedaemontousethisconfigurationfilewhenitstarts.Thisisdonebyeditingthedaemonstartupoptions:

sudonano/etc/default/hostapd

ReplacetheDAEMON_CONFlinewiththefollowing:

DAEMON_CONF="/etc/hostapd/hostapd.conf"

Finally,rebootthePiandyoushouldbeabletoconnecttotheWi-Finetworkusingtheloginusedintheconfigurationfile.YoucanthenuseeitherawebbrowserorsmartphoneapplicationtoconnecttotheLogitechMediaServerinstanceat192.168.42.1.

IftheWi-Finetworkisnotshowingupinasearch,youmayneedtouseanalternativedriver.Tocheckwhetherthisisthecase,runthefollowingcommands:

sudoapt-getinstalliw

iwlist

Ifyouseeamessagesimilartonl80211notfound,thenopen/etc/hostapd/hostapd.confandswapthecommentedoutdriverlinessothatrtl871xdrvisuncommented.Next,weneedtodownloadamodifiedversionofhostapdusingthefollowingsetofcommands:

wgethttp://www.adafruit.com/downloads/adafruit_hostapd.zip

unzipadafruit_hostapd.zip

sudomv/usr/sbin/hostapd/usr/sbin/hostapd.ORIG

sudomvhostapd/usr/sbin

sudochmod755/usr/sbin/hostapd

Oncethecommandshavefinishedexecuting,rebootthePiandyoushouldbeabletopickuptheWi-Finetwork.

SummaryInthischapter,wetookalookatsomebasicelectronicsthatweretobeusedtopowerthePiandexternaldevicesandtoamplifytheaudiofromtheaudiooutputonthePi.

Wealsotookthefirststepstodesignandmanufacturecustomenclosuresandfittingsforhardwareprojectsbyadaptinganexistingcasefortheenclosureofthespeakersystem.Inlaterprojectsinthisbook,wewillusetheseskillstomanufactureenclosuresfromscratch.

Inthenextchapter,wewilllookfurtherintodesigningandmanufacturingcustomizedenclosures,aswebuildaminitabletoparcademachine.

Chapter3.MiniRetroArcadeCabinetInthischapter,wewillbuildaminiretro-stylearcadecabinet,whichrunsaselectionofemulatorsthatcanplaygamesfromawidevarietyofgameconsolesandarcademachines.ThiswillbedoneusinganoperatingsystemcalledPiPlay(formallyknownasPiMAME).

Anarcadecabinetisessentiallyastandardcomputerandmonitorinacustom-builtcabinetusedtomimicthestyleandshapeofretroarcademachines.

Thisprojectwillalsobethefirstthatinvolvesasignificantamountofwoodworkandcarpentryinthemakingofthecabinetforthearcadesystem.Althoughitseemslikeadauntingtaskforanyonewhohasnotundertakenaprojectlikethisinthepast,theconstructionisrelativelysimpleandcanbedonewithcommonhouseholdtools.

Tocontrolthegames,wewilluseaselectionofarcadecontrolsthatarereadilyavailableonline.WewillinterfacethemtothePiusingtheGPIOportandsomesoftwarewrittenbyAdafruit.

ThisprojectisbasedonasimilarprojectbuiltbyTonyDixonatMakerSpace,Newcastle.

RequirementsForthisproject,youwillneedthehardwareandtools.Hereisthelistofthehardwarerequired:

TheRaspberryPiAUSBkeyboard(forsetuponly)ArcadebuttonsandajoystickAmonitor(andanHDMIadapterifneeded)Asheetof6mmplywood(seetheBuildingthecabinetsectionforthesizerequired)Asheetof12mmplywood(seetheBuildingthecabinetsectionforthesizerequired)Female-to-female0.1inchpinjumpers

Toolsrequiredforthisprojectarelistedasfollows:

AsolderingironandsolderWirecuttersAPozidrivscrewdriverAdrillmachineA30mmForstnerdrillbitSandpaper(80,120,and240grit)Ajigsaw

SettinguptheinputelectronicsInthissection,wewillsetuptheinputhardwaretothearcadecabinet.Thecabinetwewillbuildcomprisesajoystickandsevenpushbuttons.AllofthedevicesusedforthisaresimpledigitallogicdevicesthatcanbeconnecteddirectlytotheGPIOheaderonthePiwithoutexternalelectronics.

Firstly,wewillsoldertheconnectingwirestoeachofourarcadebuttonsandjoystick.ThebuttonsusedhavethreeconnectionsonthemthataremarkedasCOM,NC,andNO,whichstandforcommon,normallyclosed,andnormallyopen.

NoteThebuttonsandjoystickthatIhaveusedarefromaselleroneBaycalledultracabs(http://www.ebay.co.uk/usr/ultracabs)whosellsavarietyofhardwareforarcadecabinets.Whileanybuttonsandjoysticksshouldwork,Iwillbeusingtheseintheinstructions.

Inourcase,wewanttocreateacircuitwhenthebuttonispressed,soweneedtosolderwirestoCOMandNO.Inthiscase,wewillusefemale-to-female0.1inchjumperwireswithoneendremovedandstripped,asthiswillalloweasierconnectiontothepinsonthePiGPIOport,asshowninthefollowingimage:

Next,weneedtosolderthesameconnectingwiresontothejoystick.Forthis,therearefoursimilarswitchestowhatwereusedonthebuttonsaroundtheundersideofthejoystickassemblythatneedstobeconnected.

NotethattheparticularjoystickIrecommendonlyhasCOMandNOconnections,sosincethereareonlytwoconnectionsontheswitch,gettingthewiresconnectedinthecorrectwayislessimportanthere.

Here,itisworthconnectingtheCOMconnectionsofeachswitchtogetherwithshortpiecesofstandardwire,sothatweonlyneedasinglecommonwirerunningtothe

joystick.

Next,aswiththebuttons,soldera0.1inchjumperwiretoeachswitchcontactandasinglejumperwiretooneofthecommonconnections:

Oncethisisdone,theelectronicspartofthisprojectisprettymuchcomplete.WewillconnectthebuttonsandjoysticktothePilater,oncetheyaremountedonthecabinet.

BuildingthecabinetFirstly,itisimportanttohaveagoodideaofthedimensionthatweneedforeachpartofthecabinet.ThefollowingdiagramshowsthedimensionofthecabinetImadewiththeheightandwidthofthemonitor.Whileyouarefreetoadaptthedesigntowhateverstyleyoulike,beawareofthedimensionsthatarelikelytochangethroughoutthedesign.Inthefollowingdiagram,notethatallthesizesareinmm:

Notethattheanglebetweenthemonitorandjoystickpanelisnotfixed,asitwilldependonthesizeofthemonitorandjoystick/buttonpanel.Thedimensionslistedinthediagramareonlyaroughguideandyouareencouragedtodrawasidepaneloutinascaleof1:1tocheckthedimensionsbeforedecidingonthem.

NoteWhenusingpowertools,propersafetyprecautionsshouldbeundertaken.Eyeprotectionshouldalwaysbewornandmains-poweredtoolsshouldbeprotectedusingaresidualcurrentdevice(RCD).

Thefirstpartswewanttocutarethetwosidepanelsfortheenclosure.Thesewillbothbecutfroma12mmplywood.Aswewillbeusingajigsawtocutthepanels,wewillcutboththeleft-handsideandright-handsidepanelsatthesametime,sinceitisverydifficulttogetexactlythesamecuttwicewhenyou’reguidedbyeyealone.

NoteFormycabinet,IoptedtouseBirchplywood,asithasamuchnicerappearanceandisstrongerthanstandardplywood.However,itmoreexpensiveandcanbehardertoworkwith.

Forthis,weneedtoensurethatthetwosheetsofplywooddonotmoverelativetoeachotherduringthecut.Therearemultiplewaystodothis,butthewayIchosewastoscrewthetwosheetstogetheratregularintervalsjustoutsidethecutline(refertothefollowingimage).Thisisprobablyoneofthebestways,asthismethodoffixingisveryeasytoremoveandwillwithstandalotofforce(morethanyouwilleverexertonitwhilesawing)beforethesheetsstarttomove.

Onceboththesheetsofmaterialarefixedtogether,youwillneedtomarkoutthecutpathinfaintpencilmarkingsononesideofthematerial.Ensuringthatthisisasfaintaspossiblewillmakeitiseasiertoremoveanyleftovermarkingswhilesandingthepanels

downlater.

Oncethepanelshavebeencutoutasshowninthefollowingimage,theywillhavefairlyuntidyedges,especiallywhenyoucutagainstthegrainofthetoplayerofmaterial.Aseachpanelismade,itisagoodideatotakeapieceofalow-gritsandpaper(around40-60)andquicklyremoveanyuntidyedges.Whenitistimeforthepaneltobeassembledinitsfinalposition,youshouldtaketimetosandtheedgesandsurfaceswithprogressivelyhighergripsandpaperstoachieveasmoothandtidyfinish.Agoodprogressionwouldbe80,then120,andthen240.

NoteThegritclassificationofsandpaperisbasedonthenumberofabrasiveparticlespersquareinchofmaterial.Theycanrangefrom24(verycoarse)to1,000(veryfine).

Next,wewillcutthebottompanelofthecabinet.Also,cutfromthe12mmplywood,asshowninthediagramatthestartofthissection.Thewidthofthispanelwillbearoundthewidthofthemonitorplus10mm,andthedepthwillbewhateverthedesiredwidthofthecabinetis(inthecaseofthediagram,itis400mm).

Aswiththesidepanels,theyshouldbesandeddowntoremoveanyroughedges.However,asonlyoneedgewillbeexposedtothefrontofthecabinet,gettingaperfect

finishhereisnotessential.

Next,wewillattachthebottompaneltothetwosidepanels.Todothis,wewillusebothscrewsthroughthesidepanelsthatgointotheedgeofthebottompanelandseveralplasticassemblyfittingsliketheonesshowninthefollowingimage.Thiswillhelptoensureagoodquality,durablejoint.

NoteForamorepermanentfitting,PVAwoodgluecanalsobeusedonthejointsbetweentwoplywoodpanels.

First,placethebottompanelonaflatsurfaceandaligntheonesidepanelnexttothematchingedgeofthebottompanel.Next,drillaseriesofpilotholesthatarearound1-2mmsmallerthanthescrewsthatwillfixthetwopanelstogetheratregularintervalsalongtheedgeofthesidepanel.Theywillalsoscrewthesidepaneltothebottompanel,asshowninthefollowingimage.Thescrewsusedhereshouldbedome-headed,self-tappingwoodscrewsaround1.5incheslong.Here,itisimportanttoensurethatthepilotholesaredeepenoughtopreventtheplywoodfromsplittingasthescrewsareinserted.

Next,ontheinsideofthecabinet,screwseveraloftheplasticassemblyjointsatthecornerbetweenthetwopanelsbyusingcountersunkself-tappingwoodscrewsaround3/4inchlong.Ensurethataround30mmofspaceisleftateachendtogiveenoughclearanceforotherpanelsandtheirassemblyjoints,asshowninthefollowingimage.Repeatthisprocessforthesecondsidepanel:

Next,wewillcutthepanelthatwillholdthemonitorinplace.Thispanelneedstobearound150mmhigh,thesamewidthasthebottompanel,andcutfrom12mmplywood.Thiscanbemarkedoutandcutinthesamewayastheotherpanels.

Onceyou’vecutoutthepanel,followthenextdiagramtomarkoutthefourholesthatwillbeneededtoattachthemonitor.Here,IamassumingthatthemonitorusestheVESA100standard,whichisthemostcommonsizefoundon15-22inchcomputermonitors.Itwouldbeworthcheckingthisstandardwhenyou’relookingforamonitorforthisproject.VGAmonitorswiththistypeofmountingareverycommononInternetauctionsitesandoftensellverycheaply.Notethatthefollowingdiagramisnottoscaleandthatthecenterofthepanelisindicatedbytheredcross:

OncetheVESAholesaredrilled,youcanpreparethemonitortobemountedonthepanelbyremovinganydeskstandithad(theprocedurefordoingsovariesforeachmonitor;itisworthsearchingonlineifitisnotobvioustoyouhowitcanberemoved).AttachthemonitorusingfourM4machinescrewsintheholesyou’vejustdrilled,asshowninthefollowingimage.Itisimportanttouseawasheronbothsidesoftheplywoodpaneltohelpspreadtheweightofthemonitorandtopreventthescrewheadsfromdiggingintotheplywood.

Next,wewillattachthemonitormounttothetwosidepanels.Tomakethepositioningofthemonitoreasier,first,tipthecabinettoitssidesothatthemonitor’sweightissupported.Now,movethemonitorpaneluntilthemonitorisinthedesiredposition.Thisshouldleaveatleast5mmatthetopforcoolingandthebottomshouldbejustabovewherethebuttonpanelwillbe.

Now,attachthemonitorpaneltothetwosidepanelsusingtwoassemblyjointsoneachsideofthepanel.Thiswillkeepthepanelinplacefornow.However,aswiththebottompanel,weneedtoaddsomelongerscrewsthatgothroughthesidepaneltoprovideenoughsupportfortheweightofthemonitor.

Todothis,unscrewthemonitorandmarktheoutlineofthemonitorpanelontheinsideofeachsidepanelandthenremovethescrewsholdingtheassemblyjointstothesidepanels.Thiswillleaveanindicationthatthepanelwasmounted.

Next,drilltwoholesineachsidepanelthatwillbeusedtoguidethescrewsintothesideofthemonitorpanel,asshowninthefollowingimage.Itisimportantheretoensurethatthepositionoftheholeswillnotcausethescrewstocollidewiththescrewsalreadyinthepanelfromtheassemblyjoints.

Oncethisisdone,reattachthemonitorpanelwiththeassemblyjointsandusetheholesdrilledinthesidepanelstodrillpilotholesintheedgeofthemonitorpanel,similartowhatwasdoneinthebottompanel.Tofinish,screwtwoofthesamescrewsusedforthebottompanelintoeachsideofthemonitorpanelandreattachthemonitor.Bynow,thebackofthecabinetshouldlooksimilartowhatisshowninthefollowingimage:

Next,wewillcutthefront,top,andbutton/joystickpanels.Allofthesepanelscanbecutfrom6mmplywoodandthewidthofthesewillbethesameasthebottomandmonitorpanels.Theexactwidthofthesewilldependonyourdesign,basedonthediagramearlierinthissection.Onceyouhavethedimensionsofthepanels,theycanbecutinthesamewayastheotherpanels.

First,wewillattachthetoppanel.Thisshouldbemountedonthetopbetweenthetwosidepanelsandcanbeheldinplacewithtwoassemblyjointsoneachsideofthepanel,asshowninthefollowingimage.Sincethisplywoodisthinner,youwillneedtousehalfinchscrewsforthis.

Next,weneedtodrillaholeinthefrontpanelforthesingle-playerarcadebutton.Todothis,wewillusea30mmForstnerdrillbit.First,startbymarkingthecenteroftheholeforthebutton.Thiswillbeusedtoalignwiththesharppointinthecenterofthedrillbit.

Althoughholeslikethisarebestdrilledusingapillardrillordrillpress,theycanbedrilledusingahandheldelectricdrill(abattery-poweredcordlessdrillisunlikelytohaveenoughpowertodriveaForstnerbitofthissize).Itisimportanttoholdthedrillasverticalandsteadyaspossibletoensurethattheholedoesnotbecomeoutofshapebythe

drillasitmovesrelativetothepanel.

Whendrillingbyahandhelddrill,itisbesttostartslowtoensurethatthedrillgetsagoodpositioninthecenteroftheholeandgraduallyspeeduptodothebulkofcutting.Itmaytakeseveralminutestofullycutthroughthepanel,anditisworthstoppingoccasionallytocleananymaterialthathasbuiltuponthedrillbit.Becarefulwhendoingthis,asfrictioncancausethedrillbittoheatupenoughtocauseburns.Thedrilledholeisshowninthefollowingimage:

Oncetheholeisdrilled,removeanyloosematerialaroundtheedgesoftheholeusingmedium-lowgritsandpaper(either80or120)andinsertthebuttonthroughthehole.Todothis,youwillhavetoremovethemicroswitchfromthebacksideoftheswitch.IntheswitchthatIused,thisisdonebyliftingtheclipsononesideoftheswitch,whichallowsthemicroswitchtobeleveredout.

Oncetheswitchisfittedandtheedgesofthepanelaresandeddown,thepanelcanbefittedusingfourassemblyjoints,asshowninthefollowingimage.Dependingontheaccuracyofthecut,youmayfindthatthepanelisatightfitinbetweenthetwosidepanels.Ifthisisthecase,thenloosenthescrewsthatholdthesidepanelstothebottompanelsothatthesidepanelscanbemovedoutwardsslightly.Thisallowsthefrontpaneltobeinsertedeasily.

Notethatintheprecedingimage,Iused12mmplywoodforthefrontpanel.Whileitispossibletodothis,itisnotrequired.Drillingthe30mmholetakesmuchlonger.

Next,wewanttomarkthepositionofthebuttonsandjoystickonthefrontpanel.Thebestwaytodothisistoplacethepanelinpositiontoseewhichpositionwillfeelmostcomfortableorintuitivetoplay.Onceyouhavedonethis,markthepositionofthecenterofeachbuttonandthejoystick,asshowninthefollowingimage:

Nowthatwehavethepositionsofeachparttobemountedonthispanel,wecanstartdrillingtheholesforthem,startingwiththejoystick.

Withthejoystick,Irecommendthatyoudrillone30mmholefortheshaftofthejoystickandfour4mmholesforthemountingscrews.Startbydrillingthe30mmholecenteredonthemarkyoumadeforthecenterofthejoystick.Thisholewillbecutusingthe30mmForstnerbitinthesamewayastheholeforthebuttononthefrontpanel.

Oncethisisdone,insertthejoystickintotheholewiththeswitchsideonthebacksideofthepanel(youwillneedtounscrewtheredballfromthetopofthejoystickfirst)andmarkthepositionofthefourholesinthecornerofthemetalplate.Thisiswherewewilldrilltheholesthatwillbeusedtomountthejoystick.

Aftertheholeshavebeendrilled,thepanelshouldlooksomethinglikewhat’sshowninthefollowingimage:

Wewillmountthejoysticklateron.Now,itistimetodrilltheholesforourarcadebuttons.Thisisdoneinthesamewayaswasdoneforthesingle-playerbuttononthefrontpanel.

Eachofthebuttonscannowbemountedonthepanel.Whilenonessential,mountingthemsothatallofthemicroswitcheslineupparalleltoeachothermakescablemanagementeasier,asshownintheupcomingimage.

Next,wecanfastenthejoystickinpositionwithfourM3machinescrewsbyusingawasherforboththesidesofthemetalplateonthejoystick.Finally,placetheround,blackdiscthatcamewiththejoystickoverthejoystickshaftandreattachtheredball.

Bythispoint,thebackofthefrontpanelshouldlooksomethinglikewhat’sshowninthefollowingimage:

Allthatislefttodonowistoattachthebutton/joystickpaneltotherestofthecabinet.Aswithalltheotherpanels,thiscanbeeasilydonebyusingseveralassemblyjoints.

Whileitispossibletousefourjointsheretofixthepanelinasingleposition,Ifounditusefultoonlyattachthepanelusingtwojointsatthebackofthepanel(closesttothebottomofthemonitor).ThiswillallowthefrontpaneltobeliftedupforeasyaccesstothePiandwiring,asshowninthefollowingimage:

Ialsochosetouseasetofmale-to-female0.1inchjumperwirestoextendthewiresthathadbeensolderedontothebuttonandjoystickswitches.Again,thisisnotessential,butmayhelptomakewiringtheswitchestothePieasier.

Ofcourse,thisisjustonepossiblewaytodesignthecaseforthearcadecabinet.Hereareanothertwoveryuniquedesignsofasimilarproject:

http://www.instructables.com/id/NaCade-The-Naked-Raspberry-Pi-Arcade-Machine/http://www.instructables.com/id/MAME-gaming-table-with-Raspberry-Pi/

SettingupPiPlayFirst,youshouldheadtothePiPlaywebsite(http://pimame.org),downloadthelatestversionoftheOS,andwritetheimagetoanSDcard.ThisisthesameprocedurethatwefollowedwithRaspbianinthetwopreviousprojects.

OncetheimageiswrittentotheSDcard,connectanetworkcable,USBkeyboard,andmonitortothePiandpoweritup.Afterafewminutes,youshouldseethePiPlaymainscreen,asshowninthefollowingscreenshot:

Thisshowsalistofalltheinstalledemulatorsandacountofhowmanygamesareinstalledforeachoneinthesmallredsquares(obviously,foracleaninstall,therewillnotbeanygamesinstalled).

PiPlayhasawebinterfacethatcanbeusedtouploadgamestothearcadesystem.ThisisaccessedusingtheIPaddressofthePi,asshowninthefollowingscreenshot:

ThisinterfacecanalsobeusedtoshutdownandrebootthePiusingtheToolsmenu.Fornow,wewilluseROMUploadertoaddanewgametotheGameboyemulator.Thelistofalltheinstalledemulatorsisshowninthefollowingscreenshot:

NoteTherearemanywebsiteswhereROMscanbedownloaded.Ifyou’relookingforaparticulargame,thebestoptionistouseasearchenginewithaquerycontainingthenameofthegameandtheplatformyouwanttoemulateiton.

Here,wewillselecttheGameboyemulator.ThisshowsapagewhereyoucandraganddropanyROMfilesfromyourPCthataretobeuploadedtothePi:

Oncetheuploadiscomplete,thenewgamewillbeavailableinthemenuforthatemulator.

Whenanewgamehasbeenaddedforacertainemulator,PiPlaywillaskwhetheryouwanttodownloaditsinformationfromanonlinedatabase,asshowninthefollowingscreenshot.Thiswillautomaticallycorrectthenameofthegameanddownloadacoverimageifitisavailable;itisnotrequiredthatyoudothistoplayagame.

Whenanemulatorisselected,amenusimilartotheoneshowninthefollowingscreenshotisshown,whichlistsallthegamesuploadedtothePiforthecurrentemulator.Tostartone,selectitusingthearrowkeysandpressEnter.ToreturntothemainPiPlaymenu,pressEsc.

UsingthebuttonsandjoystickwithPiPlayWhiletheabilitytouseGPIOinputsasinputtoemulatorsisplannedforafuturereleaseofPiPlay,thecurrentversiondoesnotsupporttheuseofswitchesconnectedviatheGPIOportasinputtogameemulators.Hence,weneedanadditionalpieceofsoftwaretodothis.

Fortunately,AdafruithasalreadywrittenadriverthatconvertsswitchsignalsfromtheGPIOporttokeypresses(https://github.com/adafruit/Adafruit-Retrogame),whichwewilluseforourarcadebuttonsandjoystick.

First,weneedtoinstallsomerequiredprogramsandlibrariesthatwillallowustorecompiletheretrogamesoftwarewhenwemakechangestoit;thesecanbeinstalledusing:

sudoapt-getinstallgitlibexpat1libexpat1-devlibncurses5libncurses5-

dev

Next,wewilldownloadtheretrogamesoftwareandmovetothedirectoryitwassavedinbyusingthefollowingtwocommands:

gitclonehttps://github.com/adafruit/Adafruit-Retrogame.git

cdAdafruit-Retrogame

Whilethereisalreadyaprecompiledversionofthesoftwareavailable,itwillnotbesuitableforthetypeofarcadesystemwehavebuilt.So,weneedtomakeafewmodificationstothecodefirst.Usethefollowingcommandtostarteditingtheprogram:

nanoretrogame.c

Next,lookforthelinethatstartswithioStandardandreplacethelinesuptotheENDOFLISTmarkerwiththefollowingcode.NotethatifyouareusingaPiBversion1,youneedtoreplace27with21inthiscode:

ioStandard[]={

{25,KEY_LEFT},

{11,KEY_RIGHT},

{8,KEY_UP},

{9,KEY_DOWN},

{24,KEY_ENTER},

{22,KEY_S},

{17,KEY_D},

{10,KEY_Z},

{23,KEY_X},

{27,KEY_C},

{7,KEY_ESC},

{-1,-1}

};

Oncethisisdone,thecodeshouldlooksomethinglikethefollowing:

Oncethisisdone,recompilethecodeusingthefollowingcommand:

make

Thismaytakeacoupleofminutesandwilloutputamessagesimilartothefollowing:

Ifthisisthecase,thenallisgoodandyoucanmoveontothenextstep.IfyougetamessagewiththewordErrorinitanywhere,thenyouwilllikelyhaveerrorsinthesyntax

oftheprogramcode.Inthiscase,checkwhetherthecodeyouhavematcheswhat’sshownintheprecedingscreenshot.Youcanalsogetanerrorwhenoneofthelibrariesusedbythecodeisnotinstalledcorrectly;inwhichcase,tryupdatingtheinstalledpackagesusingthefollowingcommands:

sudoapt-getupdate

sudoapt-getupgrade

sudoapt-getinstallgitlibexpat1libexpat1-devlibncurses5libncurses5-

dev

Oncetheretrogameprogramiscompiledsuccessfully,weneedtoaddaudevruletoensureitscompatibilitywithemulatorsusingthelatestSDL2library.Todothis,createanewrulefileusingthefollowingcommand:

sudonano/etc/udev/rules.d/10-retrogame.rules

Onasingleline,addthefollowingcode:

SUBSYSTEM=="input",ATTRS{name}=="retrogame",ENV{ID_INPUT_KEYBOARD}="1"

Next,wewanttoensurethattheretrogameprogramstartsassoonastheOSbootsinordertoremovetheneedtoattachakeyboardtothePi.Thiscanbedonewithanadditiontotherc.localfile:

sudonano/etc/rc.local

Addthefollowinglinetothescriptjustbeforetheexit0line:

/home/pi/Adafruit-Retrogame/retrogame&

Thescriptshouldnowlooksimilartothefollowing:

ThisscriptisrunattheendoftheLinuxbootsequence,soitisagoodplacetoaddcodethatshouldbeexecutedaftertheoperatingsystemhasfinishedbooting.

Finally,rebootthePiandmoveontoconfigurethebuttonswithinPiPlay:

sudoreboot

ThenextstepistowireupthebuttonsandjoysticktotheGPIOport.Thismustbedone,asshowninthefollowingdiagram,toensurethatthebuttonmappingisasexpectedandbasedonthecodechangedinretrogame.c.ItwouldbeworthdoingthiswiringwiththepowertothePiturnedofftoreducethechancesofmistakesandpermanentdamagetothePi.

NotethatPLR1isthebuttononthefrontpanel,B1-3isthebottomrowofbuttonsfromlefttoright,andT1-3isthetoprowofbuttonsfromlefttoright.

Oncealltheconnectionshavebeenmade,theinsideofthefrontofthecabinetshouldlooksomethinglikewhat’sshowninthefollowingimage.AlsonotethatthewhiteHDMItoVGAconverterallowsyoutouseanoldPCmonitorforthisproject.

Intheprecedingimage,youmaynoticethatIampoweringthePifroma5Vpowersupply,whichisconnecteddirectlytothe5VandgroundpinsontheGPIOport.Thisisnotessential,butifyoufindthatthePibecomesunstableorhasproblemswithUSBdevicesorinmaintaininganetworkconnection,thenthismaybethecasebecausethepowersupplycannotsupplyenoughcurrent.Thiscanhappenespeciallyifyou’reusingaHDMItoVGAconverter,whichrequiresacertainamountofpowertooperate.

Oncethisisdone,repowerthePi.WhenthePibootsbackintoPiPlay,youwillnoticethatthejoystickandbutton1willalreadybeabletomovethecursorandselectemulators.However,youwillneedtoconfigurethekeymappingfortheadditionalbuttonsusedbyeachemulator.

Toconfigurethejoystickandbuttonsforacertainemulator,presstheTabkeyonthekeyboard.Thisshouldbringupamenusimilartotheoneshowninthefollowingimage.UsethearrowkeystoscrolldowntoControllerSetupandpressEnter.

ThiswillshowanothermenuthatshowsalltheemulatorsthatPiPlaycancontrolthekeymappingof.Here,itisbesttoselectasingleemulatorandassignitskeymappingindividually,forinstance,selectarcadefromthismenu.

Thiswillthenshowapreviewofthecontrollerasshowninthefollowingimageandyouwillbepromptedtopresscertainbuttonstoconfigurethekeymapping.Certainemulatorsmayhavemorebuttonsthanwhatareavailableonthecabinet.Inthiscase,theywillhavetobemappedtokeysontheUSBkeyboard.(Ihaveonlyfoundthistobethecasewithacoupleofemulators,forexample,thepauseandcreditbuttonsofMAMEemulatorshavetobemappedtokeysonthekeyboard.)

Oncethisisdone,youwillbetakenbacktothemainmenuandcanthenselectanyoftheemulatorsusingthejoystickandarcadebuttons.Notethatthetop-leftarcadebuttonisusedtoselectamenuoptionandthefront,single-playerbuttonisusedtoreturntothePiPlaymainmenu.

SummaryInthischapter,wehadagoodlookattheprocessofdesigningandbuildingacustomenclosureforaprojectbasedontherequirementsofspecificpartsthataretobeusedintheproject.

WealsomademoreuseoftheGPIOportonthePibyusingitasanadditionalinputdevicetocontrolavarietyofgamesmadeavailableonthePiPlayoperatingsystem.

Inthenextchapter,wewillusetheRaspberryPicameramoduletocreatealocation-awaretime-lapserecorderthatcanbeusedtorecordaseriesofstillimagesoveralongperiodoftime.

Chapter4.GPS-enabledTime-lapseRecorderOneofthepossibleusesoftheRaspberryPicameramoduleistherecordingoftime-lapsecaptures,whichtakesastillimageatasetintervaloveralongperiodoftime.Thiscanthenbeusedtocreateanacceleratedvideoofalong-termeventthattakesplace(forexample,abuildingbeingconstructed).

Onealterationtothisistohavethecameramountedonamovingvehicle.Usethetimelapsetorecordajourney;withtheadditionofGPSdata,thiscanprovideaninterestingrecordofareasonablylongjourney.

Inthischapter,wewillusetheRaspberryPicameramoduleboardtocreatealocation-awaretime-lapserecorderthatwillstoretheGPSpositionwitheachimageintheEXIFmetadata.

Todothis,wewilluseaGPSmodulethatconnectstothePiovertheserialconnectionontheGPIOportandacustomPythonprogramthatlistensfornewGPSdataduringthetimelapse.

Forthisproject,wewillusetheRaspbiandistribution.InstructionsonhowthisisinstalledcanbefoundinChapter1,RaspberryPiPirateRadio.

WhatyouwillneedThisisalistofthingsthatyouwillneedtocompletethisproject.Alloftheseareavailableatmostelectroniccomponentsstoresandonlineretailers:

TheRaspberryPiArelativelylargeSDcard(atleast8GBisrecommended)ThePicameraboardAGPSmodule(http://www.adafruit.com/product/746)0.1inchfemaletofemalepinjumperwiresAUSBpowerbank(thisisoptionalandisusedtopowerthePiwhennootherpowerisavailable)

SettingupthehardwareThefirstthingwewilldoissetupthetwopiecesofhardwareandverifythattheyareworkingcorrectlybeforemovingontothesoftware.

ThecameraboardThefirst(andthemostimportant)pieceofhardwareweneedisthecameraboard.Firstly,startbyconnectingthecameraboardtothePi.

ConnectingthecameramoduletothePiThecameraisconnectedtothePiviaa15-pinflat,flexribboncable,whichcanbephysicallyconnectedtotwoconnectorsonthePi.However,theconnectoritshouldbeconnectedtoistheonenearesttotheEthernetjack;theotherconnectorisfordisplay.

1. Toconnectthecablefirst,liftthetopretentionclipontheconnector,asshowninthefollowingimage:

2. Inserttheflat,flexcablewiththesilvercontactsfacingtheHDMIportandtherigid,blueplasticpartoftheribbonconnectorfacingtheEthernetportonthePi:

3. Finally,pressdownthecableretentioncliptosecurethecableintotheconnector.Ifthisisdonecorrectly,thecableshouldbeperpendiculartotheprintedcircuitboard(PCB)andshouldremainseatedintheconnectorifyoutrytousealittleforcetopullitout:

4. Next,wewillmoveontosetupthecameradriver,libraries,andsoftwarewithinRaspbian.

SettinguptheRaspberryPicameraFirstly,weneedtoenablesupportforthecameraintheoperatingsystemitselfbyperformingthefollowingsteps:

1. Thisisdonebytheraspi-configutilityfromaterminal(eitherlocallyoroverSSH).Enterthefollowingcommand:

sudoraspi-config

Thiscommandwillopenthefollowingconfigurationpage:

Thiswillloadtheconfigurationutility.ScrolldowntotheEnableCameraoptionusingthearrowkeysandselectitusingEnter.

2. Next,highlightEnableandselectitusingEnter:

Oncethisisdone,youwillbetakenbacktothemainraspi-configmenu.Exitraspi-config,andrebootthePitocontinue.

3. Next,wewilllookforanyupdatestothePikernel,asusinganout-of-datekernelcansometimescauseissueswiththelow-levelhardware,suchasthecameramoduleandGPIO.WealsoneedtogetalibrarythatallowscontrolofthecamerafromPython.

Bothoftheseinstallationscanbedonewiththefollowingtwocommands:

sudorpi-update

sudoapt-getinstallpython-picamera

4. Oncethisiscomplete,rebootthePiusingthefollowingcommand:

sudoreboot

5. Next,wewilltestoutthecamerausingthepython-picameralibrarywejustinstalled.

Todothis,createasimpletestscriptusingnano:

nanocanera_test.py

6. Thefollowingcodewillcaptureastillimageafteropeningthepreviewfor5seconds.Havingthepreviewopenbeforeacaptureisagoodideaasthisgivesthecameratimetoadjustcaptureparametersoftheenvironment:

importsys

importtime

importpicamera

withpicamera.PiCamera()ascam:

cam.resolution=(1280,1024)

cam.start_preview()

time.sleep(5)

cam.capture(sys.argv[1])

cam.stop_preview()

7. SavethescriptusingCtrl+XandenterYtoconfirm.Now,testitbyusingthefollowingcommand:

pythoncamera_test.pyimage.jpg

8. Thiswillcaptureasingle,stillimageandsaveittoimage.jpg.ItisworthdownloadingtheimageusingSFTPtoverifythatthecameraisworkingproperly.

TheGPSmoduleBeforeconnectingtheGPSmoduletothePi,thereareacoupleofimportantmodificationsthatneedtobemadetothewaythePibootsup.

Bydefault,Raspbianusestheon-boardserialportontheGPIOheaderasaserialterminalforthePi(thisallowsyoutoconnecttothePiandruncommandsinasimilarwaytoSSH).However,thisisoflittleusetoushereandcaninterferewiththecommunicationbetweentheGPSmoduleandthePiiftheserialterminalisleftenabled.Thiscanbedisabledbymodifyingacoupleofconfigurationfiles:

1. First,startwith:

sudonano/boot/cmdline.txt

2. Here,youwillneedtoremoveanyreferencestottyAMA0(thenamefortheon-boardserialport).Inmycase,therewasasingleentryofconsole=ttyAMA0,115200,whichhadtoberemoved.Oncethisisdone,thefileshouldlooksomethinglikewhatisshowninthefollowingscreenshot:

3. Next,weneedtostopthePibyusingtheserialportfortheTTYsession.Todothis,editthisfile:

sudonano/etc/inittab

4. Here,lookforthefollowinglineandcommentitout:

T0:23:respawn:/sbin/getty-LttyAMA0115200vt100

Oncethisisdone,thefileshouldlooklikewhatisshowninthefollowingscreenshot:

5. Afterboththefilesarechanged,powerdownthePiusingthefollowingcommand:

sudoshutdown-hnow

Next,weneedtoconnecttheGPSmoduletothePiGPIOport.OneimportantthingtonotewhenyoudothisisthattheGPSmodulemustbeabletorunon3.3Voratleastbeabletousea3.3Vlogiclevel(suchastheAdafruitmoduleIamusinghere).

NoteAswithanydevicethatconnectstothePiGPIOheader,usinga5VlogicdevicecancauseirreparabledamagetothePi.

Next,connecttheGPSmoduletothePi,asshowninthefollowingdiagram.IfyouareusingtheAdafruitmodule,thenallthepinsarelabeledonthePCBitself.Forothermodules,youmayneedtocheckthedatasheettofindwhichpinstoconnect:

Oncethisiscompleted,thewiringtotheGPSmoduleshouldlooksimilartowhatisshowninthefollowingimage:

AftertheGPSmoduleisconnectedandthePiispoweredup,wewillinstall,configure,andtestthedriverandlibrariesthatareneededtoaccessthedatathatissenttothePifromtheGPSmodule:

1. Startbyinstallingsomerequiredpackages.Here,gpsdisthedaemonthatmanageddatafromGPSdevicesconnectedtoasystem,gpsd-clientscontainsaclientthatwewillusetotesttheGPSmodule,andpython-gpscontainsthePythonclientforgpsd,whichisusedinthetime-lapsecaptureapplication:

sudoapt-getinstallgpsdgpsd-clientspython-gps

2. Oncetheyareinstalled,weneedtoconfiguregpsdtoworkinthewaywewant.Todothis,usethefollowingcommand:

sudodpkg-reconfiguregpsd

3. Thiswillopenaconfigurationpagesimilartoraspi-config.First,youwillbeaskedwhetheryouwantgpsdtostartonboot.SelectYeshere:

4. Next,itwillaskwhetherweareusingUSBGPSreceivers.Sincewearenotusingone,selectNohere:

5. Next,itwillaskforthedevice(thatis,serialport)theGPSreceiverisconnectedto.Sinceweareusingtheon-boardserialportonthePiGPIOheader,enter/dev/ttyAMA0here:

6. Next,itwillaskforanycustomparameterstopasstogpsd,whenitisexecuted.Here,wewillenter-n-G.-n,whichtellsgpsdtopolltheGPSmoduleevenbeforeaclienthasrequestedanydata(thishasbeenknowntocauseproblemswithsome

applications)and-GtellsgpsdtoacceptconnectionsfromdevicesotherthenthePiitself(thisisnotreallyrequired,butisagooddebuggingtool):

NoteWhenyoustartgpsdwiththe-Goption,youcanthenusecgpstoviewtheGPSdatafromanydevicebyusingthecommandwhere[IP]istheIPaddressofthePi:

cgps[IP]

7. Finally,youwillbeaskedforthelocationofthecontrolsocket.ThedefaultvalueshouldbekeptheresojustselectOk:

8. Aftertheconfigurationisdone,rebootthePiandusethefollowingcommandtotesttheconfiguration:

cgps-s

Thisshouldgiveoutputsimilartowhatisshowninthefollowingscreenshot,ifeverythingworks:

IfthestatusindicationreadsNOFIX,thenyoumayneedtomovetheGPSmoduleintoanareawithaclearviewoftheskyfortesting.Ifcgpstimesoutandexits,thengpsdhasfailedtocommunicatewithyourGPSmodule.Gobackanddouble-checktheconfigurationandwiring.

SettingupthecapturesoftwareNow,weneedtogetthecapturesoftwareinstalledonthePi.

1. First,copytherecorderfolderontothePiusingFileZillaandSFTP.2. WeneedtoinstallsomepackagesandPythonlibrariesthatareusedbythecapture

application.Todothis,firstinstallthePythonsetuptoolsthatIhaveusedtopackagethecaptureapplication:

sudoapt-getinstallpython-setuptoolsgit

3. Next,runthefollowingcommandstodownloadandinstallthepexiflibrary,whichisusedtosavetheGPSpositionfromwhicheachimagewastakenintotheimageEXIFdata:

gitclonehttps://github.com/bennoleslie/pexif.gitpexif

cdpexif

sudopythonsetup.pyinstall

4. Oncethisisdone,SSHintothePicanchangedirectorytotherecorderfolderandrunthefollowingcommand:

sudopythonsetup.pyinstall

5. Nowthattheapplicationisinstalled,wecantakealookatthelistofcommandsitacceptsusing:

gpstimelapse-h

Thisshowsthelistofcommands,asshowninthefollowingscreenshot:

Afewoftheoptionsherecanbeignored;--log-file,--log-level,and--verboseweremainlyaddedfordebuggingwhileIwaswritingtheapplication.The--gpsoptionwillnotneedtobeset,asitdefaultstoconnecttothelocalgpsdinstance,whichiftheapplicationisrunningonthePi,willalwaysbecorrect.

The--widthand--heightoptionsaresimplyusedtosettheresolutionofthecapturedimage.Withoutthem,thecapturesoftwarewilldefaulttocapture1248x1024images.

The--intervaloptionisusedtospecifyhowlong,inseconds,towaitbeforeitcapturesanothertime-lapseframe.Itisrecommendedthatyousetthisvalueatleast10secondsinordertoavoidfillingtheSDcardtooquickly(especiallyifthetimelapsewillrunoveralongperiodoftime)andtoensurethatanyvideocreatedwiththeframesisofareasonablylength(thatis,nottoolong).

The--distanceoptionallowsyoutospecifyaminimumdistance,inkilometers,thatmustbetravelledsincethelastimagewascapturedandbeforeanotherimageiscaptured.Thiscanbeusefultorecordatimelapsewhere,whateverholdsthePi,maystopinthesamepositionforperiodsoftime(forexample,ifthecameraisinacardashboard,thiswouldpreventitfromcapturingseveralidenticalframesifthecariswaitingintraffic).

Thisoptioncanalsobeusedtocaptureasetofimagesbasedaloneonthedistancetravelled,disregardingtheamountoftimethathaspassed.Thiscanbedonebysettingthe--intervaloptionto1(avalueof1isusedasdataisonlytakenfromtheGPSmodule

everysecond,socheckingthedistancetravelledfasterthanthiswouldbeawasteoftime).

Thefolderstructureisusedtostoretheframes.Whilebeingslightlycomplexatfirstsight,thisisagoodmethodthatallowsyoutotakemultiplecaptureswithouteverhavingtoSSHintothePi.

Usingthe--folderoption,youcansetthefolderunderwhichallcapturesaresaved.Inthisfolder,theapplicationlooksforfolderswithanumericalnameandcreatesanewfolderthatisonehigherthanthehighestnumberitfinds.Thisiswhereitwillsavetheimagesforthecurrentcapture.

Thefilenameforeachimageisgivenbythe--filenameoption.Thisoptionspecifiesthefilenameofeachimagethatwillbecaptured.Itmustcontain%d,whichisusedtoindicatetheframenumber(forexample,image_%d.jpg).

Forexample,ifIpass--foldercaptures--filenameimage_%d.jpgtotheprogram,thefirstframewillbesavedas./captures/0/image_0/jpg,andthesecondas./captures/0/image_1.jpg.

Herearesomeexamplesofhowtheapplicationcanbeused:

gpstimelapse--foldercaptures--filenamei_%d.jpg--interval30:Thiswillcaptureaframeinevery30secondsgpstimelapse--foldercaptures--filenamei_%d.jpg--interval30--

distance0.05:Thiswillcaptureaframeinevery30seconds,providedthat50metershavebeentravelledgpstimelapse--foldercaptures--filenamei_%d.jpg--interval1--

distance0.05:Thiswillcaptureaframeinevery50metersthathavebeentravelled

Nowthatyouareabletorunthetime-lapserecorderapplication,youarereadytoconfigureittostartassoonasthePiboots.RemovingtheneedforanactivenetworkconnectionandtheabilitytointerfacewiththePitostartthecapture.

1. Todothis,wewilladdacommandtothe/etc/rc.localfile.Thiscanbeeditedusingthefollowingcommand:

sudonano/etc/rc.local

2. Thelineyouwilladdwilldependonhowexactlyyouwanttherecordertobehave.Inthiscase,Ihavesetittorecordanimageatthedefaultresolutioneveryminute.Asbefore,ensurethatthecommandisplacedjustbeforethelinecontainingexit0:

Now,youcanrebootthePiandtestouttherecorder.AgoodindicationthatthecaptureisworkingistheredLEDonthecameraboardthatlightsupconstantly.Thisshowsthatthecamerapreviewisopen,whichshouldalwaysbethecasewiththisapplication.

Alsonotethat,thecapturewillnotbeginuntiltheGPSmodulehasafix.OntheAdafruitmodule,thisisindicatedbyaquickblinkevery15secondsonthefixLED(nofixisindicatedbyasteadyblinkoncepersecond).

OneissueyoumayhavewiththisprojectistheamountofpowerrequiredtopowerthecameraandGPSmoduleontopofthePi.Topowerthiswhileonthemove,IrecommendthatyouuseoneoftheUSBpowerbanksthathavea2Aoutput(suchpowerbanksarereadilyavailableonAmazon).

UsingthecapturesNowthatwehaveasetofrecordedtime-lapseframes,whereeachhasaGPSpositionattached,thereareanumberofthingsthatcanbedonewiththisdata.Here,wewillhaveaquicklookatacoupleofinstancesforwhichwecanusethecapturedframes.

Creatingatime-lapsevideoThefirstandprobablythemostobviousthingthatcanbedonewiththeimagesisyoucancreateatime-lapsevideoinwhich,eachtime-lapseimageisshownasasingleframeofthevideo,andthelength(orspeed)ofthevideoiscontrolledbychangingthenumberofframespersecond.

Oneofthesimplestwaystodothisisbyusingeithertheffmpegoravconvutility(dependingonyourversionofLinux;theparameterstoeachareidenticalinourcase).ThisutilityisavailableonmostLinuxdistributions,includingRaspbian.TherearealsoprecompiledexecutablesavailableforMacandWindows.However,hereIwillonlydiscussusingitonLinux,butrestassured,anyinstructionsgivenherewillalsoworkonthePiitself.

Tocreateatimelapse,formasetofimages.Youcanusethefollowingcommand:

avconv-framerateFPS-iFILENAME-c:vlibx264-r30-pix_fmtyuv420p

OUTPUT

Here,FPSisthenumberofthetime-lapseframesyouwanttodisplayeverysecond,FILENAMEisthefilenameformatwith%dthatmarkstheframenumber,andOUTPUTistheoutput’sfilename.Thiswillgiveoutputsimilartothefollowing:

ExportingGPSdataasCSVWecanalsoextractGPSdatafromeachofthecapturedtime-lapseimagesandsaveitasacomma-separatedvalue(CSV)file.Thiswillallowustoimportthedataintothird-partyapplications,suchasGoogleMapsandGoogleEarth.

Todothis,wecanusetheframes_to_gps_path.pyPythonscriptincludedinthecodeforthischapter.Thistakesthefileformatforthetime-lapseframesandanamefortheoutputfile.

Forexample,tocreateaCSVfilecalledgps_data.csvforimagesintheframe_%d.jpgformat,youcanusethefollowingcommand:

pythonframes_to_gps_points.py-fframe_%d.jpg-ogps_points.csv

TheoutputisaCSVfileinthefollowingformat:

[framenumber],[latitude],[longitude],[imagefilename]

Thescriptalsohastheoptiontorestrictthemaximumnumberofoutputpoints.Passingthe--max-pointsNparameterwillensurethatnomorethanNpointsareintheCSVfile.Thiscanbeusefulforimportingdataintoapplicationsthatlimitthenumberofpointsthatcanbeimported.

SummaryInthischapter,wehadalookathowtousetheserialinterfaceontheGPIOportinordertointerfacewithsomeexternalhardware.TheknowledgeofhowtodothiswillallowyoutointerfacethePiwithamuchwiderrangeofhardwareinfutureprojects.

WealsotookalookatthecameraboardandhowitcanbeusedfromwithinPython.Thiscameraisaveryversatiledeviceandhasaverywiderangeofusesinportableprojectsandubiquitouscomputing.

Youareencouragedtotakeadeeperlookatthesourcecodeforthetime-lapserecorderapplication.ThiswillgetyouonyourwaytounderstandthestructureofmoderatelycomplexPythonprogramsandthewaytheycanbepackagedanddistributed.

Inthefollowingchapter,wewilltakeamoreintricatelookathowtointerfacewithexternalhardwareaswebuildahometheaterPC.

Chapter5.HomeTheaterPCInthischapter,wewillcreatealow-powerhometheaterPCcapableofplayingavarietyoflocalmediafilesfromaUSBmemorystickorharddriveaswellasthecontentstoredonyourlocalnetworkandcloudservices,suchasYouTube.

Todothis,wewillusetheOpenELEC(http://openelec.tv)operatingsystem,whichisanoperatingsystemdesignedspecificallyforhometheaterPCsrunningonthePi.

WewillalsocreateacustomenclosureforthemediaPCthatwillhousea20columnby4row(20x4)LCD,whichcanbeusedbyXBMCtodisplayinformationofthecurrentlyplayingmediaorinformationrelatedtothecursorpositionintheonscreenmenu.WewillalsoincludeasetofbuttonsthatcanbeusedtocontrolXBMCwithoutaUSBkeyboardoranyotherremote;boththeseandtheLCDwillbeinterfaceddirectlytotheGPIOportonthePi.

WhatyouwillneedThisisthelistofpartsandmaterialsyouwillneedforthisproject.Theycanbepurchasedatanyelectroniccomponentsstoresandonlineretailers.

TheRaspberryPiAUSBkeyboard(forsetuponly)A600x600mmsheetofa3mmMDFA20x4LCD(www.amazon.co.uk/2004-Characters-Display-Module-Blacklight/dp/B009GXWFSM)0.1inchfemale-to-femalejumperwiresAsmallsectionofstripboard/prototypingboard(www.maplin.co.uk/p/veroboard-copper-stripboard-100x160mm-a62rl)Two10Kmultipleturnpotentiometers(http://cpc.farnell.com/1/1/24068-trimmer-24-turn-10k-m64z103kb40-vishay-spectrol.html)Arowof0.1inchpinheaders(http://cpc.farnell.com/starconn-connectors/phw-40-rv/0-1-pm-header-single-row-40-pms/dp/CN00870)Arowof0.1inchright-angledpinheaders(http://cpc.farnell.com/starconn-connectors/phw-40-rd/0-1-pin-header-right-angle-40-pms/dp/CN00871)ADCbarreljack(http://cpc.farnell.com/1/1/1498-2-1mm-dc-socket-psg01769-pro-signal.html)Sixpush-to-make(PTM)buttons(www.rapidonline.com/electronic-components/miniature-red-push-to-make-switch-78-0100)

Inthisproject,wewillalsouseanewmanufacturingtechnique:lasercutting.WhileIdon’texpectalasercuttertobeatoolthatmanypeopleactuallyown,accesstoitismorereadilyavailablethanyouthink.Itisworthcheckingwhetherthereisahackspaceinyourlocalarea.Ifso,theymayeitherhaveamachinethatyouwouldbeabletouse(oratleasthavesomeonewhocanhelpyoumachineyourdesign)ormaybeabletopointyouintherightdirectionforwhereyoucanhaveitdonelocally.Alternatively,therearemanyservicesthatallowyoutouploadadesignonlineandpaytohaveitcutfromthematerialofyourchoice.

NoteHackspacesarecommunity-organized(andusuallycommunityfunded)workspacesthatprovideavarietyoftoolsandequipmentsthatmaynotusuallybeavailabletoyou.Theyalsoprovideagoodplacewhereyoucancollaborateonprojectsandseekadvicefromtheexpertsforaproblemyouarefacinginyourownprojects.

SettingupOpenELECOpenELECisaveryminimaloperatingsystemthatispreconfiguredwiththeXBMCmediacentersoftware(http://kodi.tv)andarangeofutilitiesspecificallysetupforhomemediasharing,suchastheSambafileserver.

First,headtohttp://openelec.tv/get-openelecand(underRaspberryPiBuilds)downloadthelateststableSDimage(thetitlewillbesomethinglikewhatisindicatedinthefollowingscreenshot).Onceyouhavethefiledownloaded,decompressitandwriteittoyourSDcard.

UnderWindows,youneedtousesoftwaresuchas7-Zip(www.7-zip.org)todecompressthistypeoffile.

OnLinuxandMac,thefollowingcommandcanbeused,whereFILENAMEisthenameofthefilethatyoudownloadedfromtheOpenELECwebsite:

gzip-dFILENAME.gz

OnceyouhavetheSDimagewrittentothecard,itistimetobootthePiforthefirsttime.Here,youneedthePiconnectedtoaTVormonitor(here,IwillbeusingHDMI)anda

USBkeyboardconnectedtoit.IwillalsoconnectaUSBWi-Fiadapter,butyoucaneasilyjustuseanEthernetconnectioninsteadofWi-Fi.

Fornow,wecanpowerthePifromaUSBconnection,asweareyettoconnectanyadditionalperipheralstoit.However,lateron,weneedtopowerthePiusingamoresubstantial5VpowersupplytoprovideenoughpowerforthePiandtheLCD.

ThefirstbootandinitialsetupWhenyoufirstbootOpenELEC,itwillshowascreensomethingsimilartothefollowingscreenshot.Itmaydisplaythisforsometime,asitiscurrentlyresizingthemediastoragepartitionoftheSDcard.

WhenOpenELECboots,itwillbootstraightintoXBMC.Sincethisisthefirsttimeithasbeenbooted,youwillalsobegreetedwiththeOpenELECfirst-timesetupwizard.ThisoftentakesawhiletobedisplayedafterXBMChasstarted.

Tonavigatethemenus,simplyusethearrowkeystomovethecursorandEntertoselectamenuoption;performthefollowingsteps:

1. First,youareaskedbyOpenELECtoselecttheappropriateregionalsettings.SelectthebuttonthatdefaultstoEnglishtochangethesettingsandselectNexttocontinue.

2. Next,youareaskedtoenteranewhostnameforthemediacenter.Itisnotrequiredthatyouchangeit.However,ifyouintendtohavemultiplemediacenters,thenitwouldbeessentialasnotwodevicesshouldshareahostname.ThiswillmakeidentificationofthePionthenetworkeasier.

3. Thenextoptionasksyoutoconfigurenetworkinterfaces.AsweareusingWi-Fi,wecannotdoanythinghereyet,aswirelessadaptersaredisabledbydefaultandwiredconnectionsdonotrequireconfiguration.JustselectNexttocontinue.

4. Next,youwillbeaskedwhatserversyouwanttoenableonthePi.Bydefault,SSHisdisabledandSambaisenabled.Iwouldrecommendyoutoenableboth,asyouwillneedSSHtoconfiguretheLCDandbuttonsandSambatouploadmediatothePi.

5. Afterthisstep,theinitialconfigurationiscomplete.SelectNexttoreturntotheXBMChomescreen.

6. Fornow,thereisoneadditionalsettingthatweneedtochange.Todothis,navigatetotheSettingsoptionundertheSYSTEMmenuusingthearrowkeysandtheEnterkey.

7. Next,navigatetotheSystemmenuandselectitusingEnter.

8. Next,navigatetoInputdevicesanddisabletheEnablemouseandtouchscreensupportoption,asneitherofthesedeviceswillbeusedwithXBMCthewaywewillbeusingthem.

9. Onthismenu,settingsareautomaticallysavedwhentheyarechanged,soyoucannowuseEsctogobackuntilyoureturntothemainmenu.

ConnectingthePitoawirelessnetworkIfyouplantouseWi-Fitoconnecttoyournetwork,thenyouwillneedtofirstenableitinordertojoinyourwirelessnetwork.UsingWi-FiasopposedtoEthernetallowsyoutoinstallthemediaPCwithouthavingtoworryaboutrunninganEthernetcabletoit.However,yournetworkperformancewillbelower,soitisonlyrecommendedifitisessential.Toconnecttothewirelessnetwork,performthefollowingsteps:

1. SelecttheOpenELECoptionundertheSYSTEMmenu:

2. Fromhere,navigatetoNetworkandselecttheActiveoptionunderWirelessNetworks.ThiswillenabletheWi-Fiadapterandstartsearchingforwirelessnetworksinrange.

3. Toconnecttoanetwork,navigatetotheConnectionsmenu.Here,youshouldseealistoftheWi-Finetworksthathavebeenfoundinyourrange.Toconnecttooneofthem,navigatetoit,pressEnter,andselecttheoptionJoin.

4. Youwillthenbeaskedforthepasswordforthenetwork.TypeitinandpressEnter.Oncedone,thiswillreturntotheConnectionsmenu;youshouldnowseethatthenetworkyouselectedhasanIPaddresslistedalongsideit.Thisshowsthatthe

connectionwassuccessful.

UploadingmediafilestothePiTheeasiestwaytouploadmediatothePiisbyaccessingtheSambafilesharesthatareprovidedbythePi.

Thesharesaresplitbythetypeofcontentthatshouldbestoredonthem.Afewofthemostcommononesare:

Music:Thisisusedtostoremusicfiles,forexample,.mp3Pictures:Thisisusedtostoreimagefiles,forexample,.jpeg,.pngVideos:Thisisusedtostorevideofiles,forexample,.mkv,.mp4Userdata:ThisiswheretheXBMCconfigurationfilesarestored

WindowsOnWindows,youcanuseWindowsExplorertobrowseallsharesonaserveratonce.Todothis,pressWinKey+Rtoopentherunpromptandenter\\IP\,whereIPistheIPaddressofthePi,andclickonOK.

ThiswillopenaWindowsExplorerwindow,whichwillallowyoutobrowsethesharesonthePiandcopyfilestoandfromit,asifitwerealocalfolder.

Whenyou’vemovedthefiles,simplyclosetheExplorerwindow.

LinuxOnLinux,assumingyoualsoknowthenameoftheshareyouwanttoaddfilesto,youcanmountashareusingthefollowingsetofcommands,whereIPistheIPaddressofthePiandSHAREisthesharename:

1. First,weneedtocreateadirectorywheretheSambasharewillbemounted(knownasthemountpoint).Thisonlyhastobedoneonce.

sudomkdir/media/openelec

2. Next,usethefollowingcommandtomounttheSambasharetothejust-createdmountpoint:

sudomount-tcifs//IP/SHARE/media/openelec

3. Youwillbeaskedforapassword,butsinceOpenELECdoesnotputapasswordonSambasharedbydefault,justpressEnter.

4. Ifthecommandexitswithoutanerror,youcangoaheadandcopyfilesto/media/openelectouploadthemtothePi.Ifyoudogetanerror,thenyoumaybemissingapackageneededtomountSambashares.Thiscanbefixedusingthefollowingcommand,whichisusedtoinstallanymissingpackages:

sudoapt-getinstallsamba4cifs-utils

5. Whenyou’vemovedthefiles,youshouldunmounttheSambashareusingthe

followingcommand:

sudoumount/media/openelec

ShuttingdownthePiToshutdownthePi,youcanusethepowermenuinXBMC,whichcanbefoundinthebottom-leftcornerofthehomescreenintheformofapowersymbol.

ThiswillgiveyoutheoptiontoshutdownandrebootthePiaswellastheabilitytosetashutdowntimer,whichwillshutdownthePiafteragivenamountoftimehaselapsed.

SettinguptheLCDNowthatwehaveconfiguredOpenELEC,wecanstartaddingourownhardwaretothemediacenter,startingwiththeLCD:

1. First,wewillstartbymakingasmallboardthatwillbeusedtomounttwopotentiometers(orvariableresistors),whichwillallowtheadjustmentofthebacklightbrightnessandcontrastfortheLCD.Thisboardwillalsohaveafew0.1inchpinheadersthatwillbeusedtoconnecttheswitchesandvariouspowersupplies.

Toconstructthisboard,firsttakeapieceofstripboard(alsoknownasprototypingboard)andcuta1”x2”sectionusingapairofsidecutters.Then,cutastripof0.1”ofaright-angledpinheadertothelengthindicatedinthefollowingdiagram.Arrangethemonthecomponent-sideofthestripboard(thatis,thesidewithnocopperstrips)andsolderthemtotheboard.

Takeextracareherenottobridgethegapbetweenthecopperstrips,andensurethatthecoppersurfaceiscleanbeforeyoustartsoldering.Thesurfacecanbecleanedbyrubbingitwithsomehigh-gritsandpaper,orpreferably,wetanddrypaper.Inthefollowingfigure,notethattheyellowstripsrepresentthecopperstripsontheboard.Thisisviewedfromthecomponentsideoftheboard:

Oncethepinheadersareinplace,notethatthereisacrossonthediagram.Thismarkisusedtoindicatethatthecopperstripmustbecutinthisposition.Theeasiestwaytodothisistotakea4mmdrillbitandrotateitbyhandintheholealreadydrilledinthesoldersideuntilthecopperconnectionisremovedbythedrillbit.Ifneedbe,thiscanbeverifiedbycheckingtheresistanceacrosseithersideofthecutusingamultimeter.

2. Next,insertthetwopotentiometers,asshownintheprecedingdiagram,andsolderthemtotheboard.Whenyou’redone,youwillneedtotrimtheexcessmaterialfromthepinswiththehelpofadjacentpinsortrackstopreventthisfromshorting.

3. WecanconnecttheLCDtothePiusingseveral0.1inchfemale-to-femalejumperwiresbyfollowingthewiringinformationshowninthefollowingimage.NotethatsincetheLCDandbacklightmaydrawasignificantamountofpower,anexternal5

Vsupplyisneededherethatisconnectedtothe+5VandGNDconnectionstothefarrightoftheboardwehavejustsoldered.

Thisconnectorshouldbesoldered,asshownintheprecedingphotograph,wheretheredwireis+5Vandthewhitewireisground.Ifindoubtaboutthepinoutoftheconnector,youcanverifyitbytestingthepairsofthepinsusingamultimeter,whenthereisapoweradapterconnected.

ThefollowingtwodiagramsprovidedetailsforthewiringofthehometheaterPC.Notethatallconnectionsshouldbemadedirectlytotheotherpinwiththesamelabel,withtheexceptionofthosethatareusedforbuttons(thatis,allstartingwithB_),inwhichthepush-to-makebuttonshouldbewiredinserieswiththisconnection.

Thefollowingdiagramdetailstheconnectionstothepowerdistributionboard.Notethatthe+5VandGNDpinsonthefarrightoftheboardaretobeconnectedtotheinputpowerfromthepowersupply.

Oncethisiscomplete,itistimetoconfigurethesoftwarethatwillcommunicatewiththeLCDandallowXBMCtoupdatethedisplay.ThesoftwarethatwillactuallyinterfacewiththeLCDiscalledLCDproc.ThisispreinstalledonOpenELEC,soitonlyrequiresconfiguration.

AllthatisrequirednowistomovetheLCDd.conffileincludedwiththisprojecttothe/storage/.configdirectoryontheSDcard.ThiscanbeeasilydoneoverSFTP,aswehavedoneinthepreviousprojects.

Afteropeningthefile,youwillseethefollowingimportantlines:

Line53tellsLCDprocthatwewanttousetheHD44780driverforthedisplayweareconnectingto.Lines76-82areusedtospecifythetestthatistobeshownontheLCDastheoperatingsystembootsupandshutsdown.Line539tellstheHD44780driverthatourdisplayisconnectedtotheGPIOportonthePi.Thisconfigurationoptionisadevice-specificoptionthatwasaddedduetoitspopularitythatitusesthePiforthispurpose.Line581tellstheHD44780driverhowbigourdisplayisinnumberofcolumnsbynumberofrows.

NoteHD44780isaverycommonLCDcontrollerchipmadebyHitachi.YouwillfindeitherthisspecificchiporonethatiscommandidenticaltoitisprettymucheverycharacterLCDmodule.The16-pininterfaceisusuallyagoodsignasitcanbeusedwithdriversthatsupportHD44780.

OncetheLCDd.conffilehasbeenmoved:

1. RebootthePiusingthefollowingcommand.YoushouldbeabletoseethehellomessagedisplayedshortlyafterthePistartstoboot:

reboot

Youmayneedtoadjustthebacklightandcontrastcontrolstogettheclearesttextonthedisplay.Thiscanbedoneusingasmall,flatscrewdriverwiththesmallbrassscrewsonthetwopotentiometers.Astheyaremultipleturnpotentiometers,itmaytakeawhilebeforeyouseeanoticeabledifferenceinthedisplay.

Ifthehellomessageisnotdisplayed,thenyoumayhavemadeamistakewhenwiringtheLCD.Double-checkthewiringandrebootagain.

2. Next,weneedtoinstalltheLCDprocadd-ontoXBMCinordertoenableittocommunicatewithLCDprocandshowinformationonthedisplay.ThisisdonefromtheAdd-onsmenu,whichcanbefoundunderthemainsettingsmenuofXBMC:

3. Fromhere,selectSearch,enterlcd,andpressEnter.

ThissearchshouldfindtheXBMCLCDprocadd-on.Ifnoresultswerefound,tryrebootingthePi,asIfoundproblemswiththelistofadd-onsnotbeingupdatedifthenetworkconnectionwasjustsetup.

4. SelecttheLCDprocadd-onusingEnterandselecttheInstalloption.Thiswillnowdownloadandinstalltheadd-on.Whentheprocessiscomplete,youwillseeanotificationinthebottomrightofthescreen,andtheentryinthesearchresultswillhaveanEnabledindicatornexttoit.

5. Whenthisisdone,selecttheadd-onfromthesearchresultsagain,andselecttheConfigureoption.

Thishassomeoptionsthatcontrolhowcertaintextisdisplayed.Someoptionsyoumaywishtochangehereare:

Navigationdisplayduration:Thisisthedurationofhowlongthedisplaywill

showthemenupositionafteritischanged.Scrollmode:Thischangesthewaytextwrapsaroundthedisplay,whenitisscrolling.Itisbesttotrybothandseewhichyouprefer.Delayforscrollingtext:Thiscontrolsthespeedofthetextscrolling.Ifitissetto0,textscrollingwillbedisabled.

OtheroptionsunderBacklightandConnectionarenotasimportant,aswedonothaveabacklightthatLCDproccancontrolandwedon’twanttochangethedefaultconnectioninformation.

6. Whenfinished,saveanychangesyou’vemadetothesettingsbyselectingOK.7. Finally,youcancustomizethewayinformationisdisplayedontheLCDby

uploadinganLCD.xmlfiletothePi.ThisisthenreadbyXBMC;itdictateswhatshouldbeshownoneachlineoftheLCDinarangeofdifferentsituations.

IhaveincludedasampleLCD.xmlfileinthefilesforthisproject.ThisshouldbeuploadedtotheuserdatafolderwithinXBMC,whichcanbeaccessedeitherthroughSFTPvia/storage/xbmc/userdataorthroughSambaviatheUserdatashare.

ThereisdocumentationandsomefurthersampleLCDconfigurationfilesavailableontheXBMCwikiathttp://kodi.wiki/view/LCD.xml.

SettinguptheswitchesThenextpieceofhardwarewewillsetupisthesixswitchesthatwillbeusedforthefourdirectionkeys,back,andenter.Althoughtheycanbeeasilyremappedtowhateversetofcontrolsyoulike.

1. Thefirststephereistosolderwireswitha0.1inchfemalepinsocketatoneendtoeachswitchterminal.ThisprocessisverysimilartowhatwedidforthearcadebuttonsinChapter3,MiniRetroArcadeCabinet.

2. Oncethisisdone,itwouldbeworthwrappingtheconnectionsinsomeinsulationtapetogivethecablesextrarelieffromthestrain,asshowninthefollowingimage:

3. Next,itistimetowiretheswitchestothePi.Todothis,wewillfollowthesamewiringdiagramsusedintheprevioussectiontoconnecttheLCD.

Oncethisisdone,wecanmoveontothesoftwaresetupforthebuttons.TointerfacewiththeGPIOhardware,wewillusethesysfsbindingsthatareavailablebyreadingandwritingtofilesunderthe/sys/class/gpio/directory.ThismethodisusedbecauseOpenELECdoesnotincludethelibrarytoaccessGPIOthroughPython,andbecausetheoperatingsystemrunsmostlyfromaread-onlyfilesystem,itisdifficulttoinstallthislibrary.

4. Ifyouwishtouseadifferentbuttonmapping,thenyoucanchangeitinthelines131-136ofbutton_watcher.py:

BUTTONS['enter']=(4,'Input.Select')

BUTTONS['back']=(9,'Input.Back')

BUTTONS['up']=(27,'Input.Up')

BUTTONS['down']=(22,'Input.Down')

BUTTONS['left']=(10,'Input.Left')

BUTTONS['right']=(11,'Input.Right')

NoteNotethatfortherevision1board,theupbuttonmustbeswappedfromGPIO27toGPIO21.

Here,thefirstentryinthetupleforeachbuttonistheGPIOnumber(notthepinnumber)thebuttonisconnectedtoandthesecondentryisthecommandthatissent

totheXBMCAPIwhenthebuttonispressed.

ChangingthevaluesfortheseentriesallowsyoutoremapthebuttonstoanyfunctionssupportedbytheAPI.FulldocumentationoftheAPIisavailableontheXBMCwiki(http://kodi.wiki/view/JSON-RPC_API/v4).Hereisalistofsomecommonremotecontrolfunctionsthatcanbeused:

Input.Up:ThisnavigatesupintheGUIInput.Down:ThisnavigatesdownintheGUIInput.Left:ThisnavigatesleftintheGUIInput.Right:ThisnavigatesrightintheGUIInput.Select:ThisselectsthecurrentitemintheGUIInput.Back:ThisnavigatesbackonelevelintheGUIInput.Home:ThisreturnstothehomemenuintheGUIPlayer.PlayPause:ThispausesorresumesplaybackPlayer.Stop:ThisstopsplaybackPlayer.GoPrevious:ThistakesyoutothepreviousitemintheplaylistPlayer.GoNext:Thistakesyoutothenextitemintheplaylist

5. Onceyouhavethebuttonsmappedaccordingtoyourliking,goaheadandcopythebutton_watcher.pyscripttothe/storage/.config/directoryontheSDcard.ThisiseasilydonebyusingSFTP.

6. Whenthisisdone,usethefollowingcommandtorunthescriptandtesteachofthebuttons:

python/storage/.config/button_watcher.py

Ifalliswell,youshouldseeanoutputsimilartothefollowingontheconsoleandXBMCshouldreactaccordingtowhatthebuttonhasbeenconfiguredtodoinbutton_watcher.py.Toexitthescript,pressCtrl+C.

Ifyouseeanerrorstatingthatthedeviceisbusyorunavailable,checkthemappinginbutton_watcher.pyandensurethatalloftheGPIOportnumbersarecorrectandthatyou

havenotmappedabuttonoveranotherbuttonortheLCD.

1. Whenthescriptisworkingasintended,itistimetoconfigureitinordertostartitwhenOpenELECbootsup.ThisisdoneinaslightlydifferentmannerinOpenELEC,asopposedtoRaspbian.First,wemustcreateascriptthatOpenELEClooksfortorunonstartup:

touch/storage/.config/autostart.sh

chmod+x/storage/.config/autostart.sh

nano/storage/.config/autostart.sh

2. Here,thefirstcommandcreatesthefile,thesecondcommandmakesthefileexecutable,andthethirdopensitinnanoforustoedit.Here,wewilladdthefollowinglinetotheendofthefile:

#!/bin/sh

python/storage/.config/button_watcher.py&

3. ThistellstheshelltorunthePythonscriptinthebackground(notedbythe&trailing).Now,simplyexitnanousingCtrl+XandrebootthePiusingthefollowingcommand:

reboot

WhenthePihasbootedbackintoOpenELECandXBMCisrunning,youshouldnowbeabletousethebuttonsrightaway.

FinalassemblyThefirstthingyoumustdobeforegettingthepartsforthecasemachinedisdecidewhichvideoconnectoryouwilluse.YoucanuseeitherHDMIorcompositevideoand3.5mmaudiojacks.ThiswilldeterminewhichsideofthePiisnexttothesideoftheenclosure,sincethetwovideooutputsareontheoppositesidesoftheboardandassuch,therearedifferencesbetweenthedesignsofeachenclosure.

Forbothtypesofenclosure,thefilesintheenclosurefolderinthefilesforthisprojectmustbemachined.Therearetwofolders,hdmiandcomposite_video,thatcontainthepartsspecifictoeachvideooutputtype.

Thepartsneededforeachtypeareshowninthefollowingfigure:

Thetwoenclosurevariants:compositevideoontheleftandHDMIontheright

Onceyouhavethepartsyouneedfortheenclosuretypeyouhavedecidedtobuild,itwouldbeagoodideatoremoveanywiringalreadydonesofartomaketheassemblyprocesseasier.

Oncethisisdone,performthefollowingsteps:

1. StartbymountingtheLCDintothefrontpanel.ThisshouldbedonewithfourM4machinescrewsandnuts.EnsurethatyoudonotovertightenthenutsandputexcessstrainonthePCB.

ThefrontpanelissymmetricalwiththehorizontalcenteroftheLCDmodule,soitdoesnotmatterwhichsideorwhichorientationthefrontpanelisinwhenyoumounttheLCD.Dotrytopickthesidethatisbetterlooking.

2. Next,mounteachofthepushbuttonsinthetoppanelusingthewashersandnutsthatcamewiththebuttons,asshowninthefollowingimage:

3. Next,wecanassemblethetop,bottom,back,andsidepanelsthatwillincludethecutoutforthevideoconnector,thatis,ifyouarebuildingthecompositevideoversionoftheenclosure,youwillhavetheoppositesideattachedtowhatisshowninthefollowingimage:

4. Aroundtheedge,themiddlepanelsconnecttothesidepanels.Here,youwillseeaseriesoffittingssimilartothoseshowninthefollowingimage.TheserequireanM4nuttobeinsertedintotheslotandanM4machinescrewtobeinsertedthroughtheholeinthesidepanel,asshowninthefollowingimage:

Thescrewfitting—beforebeingtightened(left)andafterbeingtightened(right)

NoteItisimportantnottoovertightenthesescrewfittings,astheloadistakenentirelybytheapproximately2mmofMDFthatisincontactwitheachnut.

5. Next,mountthePiintotheenclosureusingtwoM4machinescrewsthroughthebottompanel.Here,itisusefultouseastackofwatcherstospacethePCBapartfromthebottompaneltohelpremovestraininthePCB.Beforedoingthis,itisimportanttoverifythatthewashersyouintendtousearesmallenoughtopreventcausingashortwithanyexposedcomponentsatthebottomofthePi.

ThisisalsoagoodpointtostartrewiringthePi,LCD,andthesmallboardwemadetocontroltheLCDbrightnessandcontrast.

6. Next,wewillrewirethebuttonstothePiasbeforeandattachthetoppanelinthesamewayastheotherthree.

Bythispoint,themediacenterwiringshouldbecomplete.Now,youcanmounttheDCbarreljackthatwillbeusedtopowerthePiexternallytothebackpanelusingthenutandwasherthatwassuppliedwithit.

7. Atthispoint,youarereadytoattachtheremainingsidepanelandgivethemediacenteratestbeforefasteningtheremainingscrewfixings.

8. IfallseemstobegoodandboththeLCDandbuttonsworkasintended,youcangoaheadandfastentheremainingsidepanelusingthesamescrewfixingsthatwereusedfortheotherside.

Here,itisimportanttokeeptheenclosuretiltedsothatifoneofthenutsfallsoutoftheslot,itwillfalloutsideoftheenclosureratherthaninsideit.

SummaryInthischapter,welookedatyetmorehardwarethatcanbeusedwiththeGPIOportonthePiandadditionalwaysinwhichitcanbecontrolledbysoftware.

Wealsotookalookatanotherapplication-specificoperatingsystemavailableforthePi,howtheycanbeverydifferenttothegeneralRaspbianOS,andhowtheapproachtosolveaproblem(suchasthebuttonsinthisproject)hastobechangedbasedontheenvironmentinwhichitwillbeimplemented.

Wealsotookaquicklookathowtouselasercuttingtomanufactureprofessionalqualityenclosuresquicklyandeasily.Thisisaveryversatilemanufacturingprocessandcanbeusedtocreatesomeveryimpressiveproducts.Iwouldhighlyrecommendyoutoconsideritinanyprojectsyoumayundertakeinthefuture.

Inthenextchapter,wewilllookathowtointerfacetheRaspberryPiwithavarietyofsensorsusingtheArduinoprototypingplatformtocreateanoutdoorweatherstation.

Chapter6.OutdoorWeatherStationInthischapter,wewillmakeanoutdoorweatherstationthatisaccessibleovertheInternet,whichwillallowremotemonitoringandrecordingoftheweatherconditions.

Todothis,wewillhavealookatanewskillthatwillallowustotakesomeexistingsensorsandadaptthemforuseinourproject—reverseengineering.Thisisessentiallytheprocessoftakingapartofanexistingproductandderivingthecommunicationmethodbetweenitandtherestoftheproduct,sothatyoucanreplaceeitheraspecificpartorawholeproduct.

WewillalsotakeaquicklookathowtousethePiasawebserverandthemethodusedtodevelopanddeployaPythonwebapplication.

WhatyouwillneedThisisalistofallthepartsyouwillneedinordertocompletethisproject.Mostoftheseareavailableathigh-streetelectroniccomponentsstoresandonlinedistributors:

ARaspberryPiAWi-FidongleAlongmicroUSBcableAclear/translucentTupperwareboxADHT11(www.adafruit.com/product/386)orDHT22(www.adafruit.com/products/385)sensorBMP180(www.adafruit.com/product/1603)AMaplinanemometer(windspeedsensor)(www.maplin.co.uk/p/maplin-replacement-wind-speed-sensor-for-n96fy-n82nf)AMaplinwinddirectionsensor(www.maplin.co.uk/p/maplin-replacement-wind-direction-sensor-for-n96fyn96gy-n81nf)AMaplinraingauge(www.maplin.co.uk/p/maplin-replacement-rain-gauge-for-n25frn96fyn96gy-n77nf)AnArduinoUno(www.adafruit.com/product/50)Aselectionofresistors(www.maplin.co.uk/p/e12-025w-resistor-610-piece-pack-fa08j)A1inchsquaresectionofastripboard(www.maplin.co.uk/p/veroboard-copper-stripboard-100x160mm-a62rl)Arowoffour0.1inchpinheadersAstripofterminalblocksMale-to-malepinjumperwiresFemale-to-femalepinjumperwires

NotethateventhoughIhavespecificallylistedanArduinoUno,anystandard8-bitAVR-basedArduinoshouldworkfineforthisproject,forexample,theUno,Mega,Nano,andDuemilanove.

IhavealsospecifiedtwodifferentDHTsensorsthatcanbeused.TheonlyrealdifferencebetweenthemisthatDHT22hasawideroperatingrangethanDHT11;DHT11canreadtemperaturesbetween0and50degreesCelsiusandhumiditybetween20and80percentRH(relativehumidity),whereastheDHT22canreadtemperaturesbetween-40to80degreesCelsiusandhumiditybetween0to100percentRH.

Wewillmakeuseofdifferentvaluedresistorsacoupleoftimes.Thesearesmalldevicesthatareusedtolimittheflowofcurrentthroughacircuit.TheirresistanceismeasuredinOhmsandisdenotedbyΩ.Sincethesedevicesdonothavetheirresistancevalueprintedonthem,acolorcodemustbeused.Tofindthecolorcodeusedtodenoteaparticularresistance,agoodreferencechartcanbefoundatwww.digikey.co.uk/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-band.Throughoutthischapter,resistorsarereferredtobybothvalueandcolorcode.

NotethatwewillnotusethefullpackofresistorsIprovidedalinkto.However,theyareveryhandytohaveashavingtoorderpartslikeresistorsasandwhentheyareneededslowsdownthistypeofelectronicsproject.

ReverseengineeringtheMaplinsensorsBeforewestartcreatingourownelectronicstotakereadingsfromthesesensors,weneedtostartwithalittletheoryandtestingtogetagoodunderstandingofhowthesesensorsworkandhowwewillbeabletointeractwiththem.

UnderstandingthesensorsTostartwith,let’stakealookatthemechanicsandelectronicsusedinthedevicestoknowhowtheofficialdevicewouldhavetakenmeasurementsfromthem(notethatyoudonothavetodisassembleyoursensorshere).

Wewillstartwithprobablythesimplestofallthree—theraingauge.Ifweunclipthetopsection,wewillbeabletonoticeaseesaw-likemechanismthatcarrieswaterfromthespoutofthefunnelinthetopcoveredsectiontoeithertheleft-handsideorright-handsideofthesensor,dependingonthepositionoftheseesaw.

Witheachmovement,theseesawtriggersareedswitch,asmallswitchthatisactivatedusingamagnetinthecenteroftheseesawthatcompletesacircuit,whichcanbemonitoredbythemeasurementdevice.

Whilethismethodisquiteeffectiveatmeasuringwhenthereisrainfall,itcannotaccuratelydeterminehowmuchrainfalltherehasbeen,asthiswillpartiallydependontherateofrainfall.Sincethisrelationshipisnotlinear,itwouldtakemoreeffortthanwhatitisworthtoderive.Simplyrepresentingthenumberoftimestheswitchistriggeredoveragivensampletimewillbesufficientforourweatherstation.

Let’smoveontotheanemometernow.Thisisthedevicethatwillbeusedtodeterminehowfastthewindisblowing.Ifyouremovethethreescrewsatthebottomofthesensor,wecannoticethatithasasimilarreedswitch.Byattachingamultimeterinresistancemode,wecantellthattheswitchpulsesclosedcircuitandthenopencircuittwiceperrevolutionofthesensor.

Giventhatweareabletomeasuretimerelativelyaccurately(uptomillisecondprecision)usingArduino,wecanusethesignalfromthisreedswitchtomeasuretherevolutionsperminute(RPM)travelledbytheanemometer.Then,wecanmultiplythisbythecircumferenceoftheanemometermeasuredfromthecenterofthecupstofindthedistancetravelledbyasinglecupinoneminute.Finally,convertthisresulttoastandardunit(inourweatherstationthiswillbeinmilesperhour(MPH))togetthewindspeed.

Thefinal(andmostinteresting)sensoristhewinddirectionsensor.Thisisessentiallyavanethatpointsinagivendirectionifforceisexertedonthesideofthevanebythewind.Ifweopenthebottomofthissensor,wecanseeaprintedcircuitboard(PCB)thatcontainseightreedswitchesandasocket,whichisusedtoconnecttheanemometer.

IfyouremovethisPCB,youcanseethatthetwomiddleconnectionsofthesocketareconnecteddirectlytothemiddletwoconnectionsofthecablerunningfromthewinddirectionsensor,leavingjusttheoutertwowiresofthecableforthedirectionsensor.

OnthereversesideofthePCB,youwillalsonoticeeightresistorsmarkedwithagivenuniqueresistanceonthePCB.Here,everyreedswitchhasitsownresistance(asshowninthefollowingcircuitdiagram),andbecauseofthespacingoftheswitches,onlyonecanbeactivatedatonce.Therefore,bymeasuringtheresistanceacrossthecircuit,youcansetthepositionofthedirectionsensoraccurateto45degrees.

Nowthatweknowexactlyhoweachofthesensorswork,wecanstartinterfacingthemwithourownelectronics.Sincethisinvolvestheneedforaccuratetimingtomeasurethewindspeed,wecannotusetheRaspberryPitodirectlytakereadingsfromthesensors,asthePirunsascheduledoperatingsystem.Thismeansthatagiventaskcanbestoppedandrestartedatrandomtimeswithoutnotice,whichcausesproblemswhenyouhavecodethatmustkeepanaccuratetrackoftime.

Arduino,however,isareal-timesystem.Thismeansthatthecodeyouwritewillneverbestoppedorpaused(withtheexceptionofinterrupts).Thisallowsyoutoensurethatcertainpartsofitwillbeexecutedinagivenamountoftime.ArduinoalsosupportshardwareinterruptsonitsGPIOs,whichallowafunctiontobecalledwheneverthestateofagivenpinchanges.Thiswillbeusedwithboththerainsensorandanemometertokeepaprecisetrackofthereadingstakenfromthesesensors.

Althoughitisnotoriginallysoldasaweathersensor,wewillalsobeincludingalight-dependentresistor(LDR),whichwillbeusedtomeasureambientlightlevels.Asthenamesuggests,thisisessentiallyaresistorthathasaresistancethatvariesdependingontheintensityofthelighthittingitssurface.

Sincethisisananalogueoutput(aswiththewinddirectionsensor),wecannotusethePitotakereadingsfromit,astheGPIOpinsonthePiareonlydigital,whereasArduinohasseveralanalogueinputsthatcanbeusedwithsensorssuchasthis.

NowisagoodtimetogooversomeofthetheoryofhowtheinputstomicrocontrollerssuchasArduinowork.Withbothofourdigitalinputshere,wewillessentiallyconnectaswitchbetweentheinputpinandgroundpin.ThechipusedonArduinohasapull-upresistoroneachpin,whichcanbetoggledinthesoftware.Thiscanbeusedtoessentiallymakethereadingfromthepinreadhighunlessthereisapathtothegroundwithalowerresistancethanthepull-upresistor,whichinourcasewillbethereedswitchesthathavenegligibleresistance.

Withtheanalogueinputs,wewilluseanadditionalresistortocreatewhatiscalledapotentialdivider.Thisisacircuitthat,asthenamesuggests,outputsavoltagethatissomewhereinbetweentwoinputvoltages,inourcase,5Vandground(0V).Thepotentialdividermakesitpossibleforamicrocontrollertomeasureresistancebyfirstconvertingittovoltage.

WiringNowthatwehaveanideaofhowoursensorswork,wecanstarttocreatethecircuitthatwillallowustointerfacewiththesensors.Sincealotofthesensorsarequitesimple,thisisarelativelyeasytask.

Firstly,weneedtopreparetheMaplinweathersensorstobeconnectedtoArduino.Whilethiscanbedonebypurchasingthecorrecttypeofsocketfortheconnectorstheycomefittedwith,itwillbeeasierinthiscasetosimplycutthemoffandconnectthemusingstripsofterminalblocks.Todoso,performthefollowingsteps:

1. Cutthetwoconnectorsofftheendsofthelongcablesthatareconnectedtotheraingaugeandwinddirectionsensor.Donotremovetheconnectionfromtheanemometerasthisconnectsittothesocketonthewinddirectionsensor.

2. Removearound1-2inchesofthegreyinsulationtoexposethecoloredwires.3. Striparound10mmofinsulationfromeachofthecoloredwires.4. Connectthetwowiresfromtheraingaugetoonesideofastripoftwoterminal

blocks.5. Connectthefourwiresfromthewinddirectionsensortoonesideofastripoffour

terminalblocksintheorderblack,red,yellow,andgreen.Thisshouldbethesameorderforthewiresarrangedinsidethecable.

6. Inserta1kΩresistor(color-codedasbrown,black,andred)betweentheblackandredwirescomingfromthewinddirectionsensoronthesamesideasthemontheterminalblock.

7. Ontheothersideofeachoftheterminalblocks,attachamale-to-malepinjumperwire.Notethatthecolordoesnothavetomatchwiththatofthewirefromthesensors.Wheneverwerefertothesewires,wewillrefertothembythecolorofthewirefromthesensor.

Bynow,thewiringfromthesensorsshouldlooksomethinglikewhatisshowninthefollowingimage:

Next,wewillpreparetheLDR:

1. TakeastripofthreeterminalblocksandconnecttheLDRtothecenterandtheleftmostterminal.

2. Onthesameside,connecta4.7kΩresistortotherightmostterminalandthecenterterminal.

3. Ontheothersideoftheterminalblock,connectamale-to-malepinjumperwiretoeachterminal.

Now,theterminalblockwiththeLDRshouldlooksimilartothefollowingimage:

Nowthatwehavethecircuitsrequiredforoursensorsbuilt,wecanconnectthemtotheArduino,asshowninthefollowingdiagram.ThissamewiringdiagramwillworkforthemajorityofArduinoboards,includingtheUno,Mega,Leonardo,andDuemilanove:

SettingupyourArduinoThefinalsteptobetakenforthesensorstoworkisuploadingthesoftwarethatwillmonitorthesensorsandreportinformationbacktothePiviayourArduino.Todothis,weneedtofirstdownloadandinstallversion1.0.6oftheArduinoIDEfromhttp://arduino.cc/en/main/software.Whenitisinstalled,followtheseinstructionstocompileanduploadthecodetoyourArduinoandperformthefollowingsteps:

1. ConnectyourArduinotoyourcomputerandopentheArduinoIDE.2. SelectFileandOpenandbrowsetotheMaplinWeatherInstrumentDriverfolderin

theprojectfiles.OpentheArduinosketchinsidethatfolder.Whenloaded,itshouldlooksomethinglikethefollowingscreenshot:

3. SelectthetypeofArduinoonwhichyouwillbeuploadingtheprogrambynavigatingtoTools|Board.

4. SelecttheserialportyourArduinoisattachedtobynavigatingtoTools|SerialPort.5. Now,clickontheuploadbuttoninthetop-leftcorneroftheArduinoIDE.Thisisthe

roundbuttonwithanarrowpointingtotheright.TheArduinoIDEwillthengiveamessagethatitisuploadingthesketchtotheboard,asinthefollowingscreenshot:

Assumingthattheuploadiscompletedsuccessfully,youshouldseethemessageDoneuploadingintheIDE,asshowninthefollowingscreenshot:

Ifyougetanerrorhere,thencheckwhetheryourboardandserialportoptionsarecorrect.Iftheerrorstillpersists,thendisconnectyourArduinoandrestarttheArduinoIDEandtryagain.Thisusuallyfixesanyproblemsthatoccurhere.

Oncetheuploadiscomplete,youcanopentheserialmonitorusingthebuttoninthetop-rightcorneroftheArduinoIDEthathasthemagnifyingglasssymboltocheckwhetherthesensorsareworkingcorrectly.Here,youshouldbeabletomanuallymovethesensorsandseetheoutputprintedtotheserialconsole.

Note

Inregardstowinddirection,thedirectionisrepresentedbyavalueof0to7,where0isnorth.Thevalueincreasesin45degreeincrements,so1isnortheast,2iseast,andsoon.Thisgoesonupto7,whichisnorthwest.

Thefollowingscreenshotdisplaystheoutputprintedintheserialconsole:

SettinguptheremainingsensorsNowthatwehavetheMaplinsensorsandtheLDRworkingproperly,usingtheArduinoboard,wecanturnourfocustotheremainingsensorsthatwillmeasuretemperature,humidity,andthebarometricpressure.

Forthis,wewilluseDHT11orDHT22tomeasurethetemperatureandhumidityandBMP180tomeasurethebarometricpressure.ThesedevicescanbeinterfaceddirectlytoandpoweredfromtheGPIOportonthePi.

DHT11/22DHT11andDHT22useaone-wirecommunicationprotocoltosenddatabacktothePi,whichrequiresanadditional10K(brown,black,andorange)resistortobeaddedbetweenthedataand3.3Vpinsonthesensor.TheeasiestwaytodothisisbymountingtheDHTsensor,resistor,andarowofmalepinheadersonasmallsectionofastripboard,asshowninthefollowingdiagram:

Oncethisiscomplete,theboardshouldlooksimilartothefollowingimage:

Thecoppertracksrunverticallyfromthetopoftheprecedingimagetothebottom.Asthisissimplyataskofaddingaresistoracrosstwotracks,thereisnoneedtocreateanybreaksinthecoppertracks.

NowthatwehaveaboardfortheDHT11/22sensor,wecanmakethefollowingconnectionstothePiGPIOportbyusingfemale-to-femalepinjumperwires:

Pin1(theleftmostpinintheprecedingimage)tothePipin6(GND)Pin2shouldnotbeconnectedPin3tothePipin7(GPIO4)Pin4(therightmostpinintheprecedingimage)tothePipin1(3.3V)

Oncethewiringiscomplete,wecannowconfigurethesoftwarefortheDHT11/22sensorwiththefollowingsteps:

1. First,installsomepackagesthatwillbeneededtosetupthedrivers:

sudoapt-getinstallbuild-essentialgit

2. Next,clonetherepositoryfortheAdafruitdriverandtheBMP180sensor:

gitclonehttps://github.com/adafruit/Adafruit_Python_DHT.git

3. Changethedirectorytotherepositorywejustclonedandrunthesetupscript:

cdAdafruit_Python_DHT

sudopythonsetup.pyinstall

4. Toensurethatthesensorisworkingcorrectly,changethedirectorytotheexamplesdirectoryandrunthesamplescript.Notethatifyou’reusingtheDHT22sensor,youwillneedtochange11to22inthefollowingcommand:

cdexamples

sudo./AdafruitDHT.py11/224

Assumingthateverythingwentasitshould,youshouldseeanoutputsimilartothefollowingscreenshot,withthereadingstakenfromthesensor:

Ifthisoutputisnotproduced,gobacktothewiringandsetupstepsandensurethatthesensoriswiredandconfiguredcorrectly.Itisworthdouble-checkingthesolderingonthestripboardtoensurethatthesensoriswiredwiththecorrectpinandthattherearenosolderbridgesbetweenthetracksonthestripboard.

BMP180TheBMP180sensorcomesalmostreadytouseandrequiresnoexternalcircuitrytoconnectittothePi,asitusestheverycommonandstandardizedI2Cbus.Theonlyassemblysteptoperformhereistosoldertherowof0.1inchpinheadersontothePCB.BecarefulwhenyoudothisanddonotgettheirontooclosetoanyofthecomponentsalreadymountedonthePCB.

Oncethepinsareinplace,wecanthenwirethesensortothePi.ThisisdonebymakingthefollowingconnectionsbetweenthesensorPCBandthePiGPIOheaderbyusingfemale-to-femalepinjumperwires:

VINtothePipin17(3.3V)GNDtothePipin25(GND)SDAtothePipin3(I2C1SDA)SCLtothePipin5(I2C1SCL)

Oncethewiringiscomplete,wecannowconfigurethesoftwarefortheBMP180sensor:

1. Editthe/etc/modulesfiletoenablethekernelmodulesthatwillallowustousetheI2CinterfacebusontheGPIOheader:

sudonano/etc/modules

2. Addthefollowinglinestothefile:

i2c-bcm2708

i2c-dev

Theoutputshouldlooklikethefollowingscreenshot:

3. InstallsomepackagesthatwillallowustousetheI2CbusfromPythonandatoolthatwecanusetodetectwhichdevicesarecurrentlyconnectedtothebus:

sudoapt-getinstalli2c-toolspython-smbus

4. Next,weneedtocheckwhetherthe/etc/modprobe.d/raspi-blacklist.conffileexists,andifso,therearesomelinesthatmustbecommentedout.Wecancheckwhetheritexistsbyopeningthefileinnano;ifitdoesnotexist,thenanoeditorwindowwillbeempty:

sudonano/etc/modprobe.d/raspi-blacklist.conf

5. Ifthefileisempty,youcanskipthenextstep,otherwise,commentoutthefollowinglines:

blacklistspi-bcm2708

blacklisti2c-bcm2708

Thefileshouldlooksimilartothefollowingscreenshot:

6. Atthispoint,weneedtorebootthePitoloadthenewdrivers:

sudoreboot

7. OncethePireboots,usethefollowingcommandtocheckwhethertheBMP180sensorhasbeendetectedbythePicorrectly:

sudoi2cdetect-y1

Ifso,youshouldseeanoutputsimilartothefollowingscreenshot:

8. AssumingthatthedeviceisnowbeingdetectedcorrectlyontheI2Cbus,wecanclonetherepositoryforthedriverthatwillinterfacewithitoverthebuswiththefollowingcommand:

gitclonehttps://github.com/adafruit/Adafruit_Python_BMP.git

9. Changetothedirectoryforthedriverwejustdownloadedandrunthesetupscript:

cdAdafruit_Python_BMP

sudopythonsetup.pyinstall

10. Toensurethatthedriveriscommunicatingwiththesensorcorrectly,changetotheexamplesdirectoryandruntheexamplePythonscript:

cdexamples

sudopythonsimpletest.py

Thisshouldgiveanoutputsimilartothefollowingscreenshotwiththereadingstakenfromthesensor:

Ifyoudidnotgetthisoutput,thenyoumayneedtodouble-checkthewiringbetweenthesensorandPi.IfthatlooksOK,thenitisworthrebootingthePiandtryingagain.

TheweatherstationwebapplicationTomakethedatawerecordfromtheweathersensorsabitmoreaccessible,wewilluseawebapplicationwritteninPythontodisplaythecurrentandhistoricaldatarecordedfromourweatherstation.

Todothis,wewillmakeuseofaPythonwebapplicationframeworkcalledFlask(http://flask.pocoo.org/),anapplicationservercalledGunicorn(http://gunicorn.org/),andareverseproxyservercalledNginx(http://nginx.org/).

Thewebapplicationwillhavetwopages,onewillshowthecurrentweatherconditionsandtheotherwillshowthehistoryoftheweatherconditionsoveragiventimerange.Tohelpvisualizethedataonboththepages,wewillusetheGoogleChartsAPI(https://developers.google.com/chart/).ThisisaJavaScriptAPIthatallowsthecreationofinteractivechartsonawebpage.

DeployingtheapponthePiIt’snowtimetodeployourwebapplicationonthePi.Todothis,wewillusetheNginxreverseproxyserverandtheGunicornwebapplicationservertohosttheapplication.Here,Gunicornistheserverthatactuallyhoststheapplicationandrelatedfiles,andNginxisanintermediateserverbetweentheGunicornandtheclientthatisusedtoforwardrequestsfromaclienttothecorrectwebserver.

AfterloggingintothePioverSSHanduploadingconfig_filesandweather_station_webapptothe/home/pidirectory,theprocesstoconfigurethewebapplicationisasfollows:

1. Installsomeprerequisitepackages:

sudoapt-getinstallpython-pippython-devgunicornsupervisornginx

2. ClonetherepositoryforFlask,thePythonwebapplicationframeworkthatourwebappisbuiltwith:

gitclonehttps://github.com/mitsuhiko/flask.git

3. ChangetothedirectoryfortherepositorywejustclonedandinstallFlaskonthePi:

cdflask

sudopythonsetup.pyinstall

4. CopytheconfigurationfileforNginxtothedirectoryofalltheavailablesites:

sudocpconfig_files/nginx/weather-station.conf/etc/nginx/sites-

available/weather-station.conf

5. Createasymboliclinktothesiteconfigurationfromthesites-enableddirectory.ThistellsNginxthatitshouldhandlerequestsforthissite:

sudoln-s/etc/nginx/sites-available/weather-station.conf

/etc/nginx/sites-enabled/

6. RemovethedefaultsitethatNginxhostswhenitisfirstinstalled:

sudorm/etc/nginx/sites-enabled/default

7. Oncealltheconfigurationisdone,itcansavealotofdebuggingtimetohaveNginx.Verifyitsconfiguration,whichcanbedonebyusingthefollowingcommand:

sudonginx-t

Assumingthattheconfigurationwasvalidatedcorrectly,youshouldseearesultsimilartothefollowingscreenshot.Ifnot,gobackthroughtheconfigurationstepsandensurethattheconfigurationisperformedcorrectly:

8. Assumingthattheconfigurationisvalidatedsuccessfully,youcannowrestarttheNginxserviceforittostarthandlingrequestsforourwebapp:

sudoservicenginxrestart

9. Next,changetothedirectoryforthewebapp:

cd~/weather_station_webapp

10. Beforewestarttoservethewebapp,weneedtoinitializeanemptydatabasetorecordmeasurements.Thiscanbedoneusingthefollowingcommand:

flask--app=weather_station_webappinitdb

11. Now,wearereadytotestthewebapplicationbyrunningGunicorn,whichcanberunusingthefollowingcommand:

gunicorn-b127.0.0.1:5000weather_station_webapp:app

Here,Gunicornisservingthewebapplicationonport5000onthelocalloopbacknetworkinterface,whichisonlyavailabletothePi.Then,arequestcomesinfromanexternalclientonport80(thestandardportforwebpagestobeserved).Nginxforwardsthistrafficto127.0.0.1:5000,wheretherequestisthenprocessedbyGunicorn.

Totestwhetherthisisworkingproperly,browsetotheIPaddressofthePifromanothercomputeronthesamenetworkasthePi.Youshouldbegreetedwithapagesimilartotheupcomingscreenshot.

IfyoureceiveapagewithaBadRequesterrormessage,thenyoumayneedtorebootthePiandtrythelaststepagain.IfyoureceiveInternalServerError,thenyoumayneedtorunthecommandtoinitializethedatabaseagain.

Assumingthatthewebappisloadedcorrectly,wecannowperformthefinalstep,whichwillstarttheGunicornserverautomaticallywhenthePiboots.Todothis,wewillusetheSupervisor(http://supervisord.org/)application,whichisaprocesscontroltoolthatmakesthecreationofdaemoninstancesofprogramsveryeasy,andperformthefollowingsteps:

1. First,weneedtocopytheconfigurationentryforthewebapplicationintotheSupervisorconfigurationdirectory:

sudocpconfig_files/supervisor/weather-station-webapp.conf

/etc/supervisor/conf.d/weather-station-webapp.conf

2. Next,runthissetofcommandstoupdatethesuperuserconfigurationandstartthewebapplicationasabackgroundprocess:

sudosupervisorctlreread

sudosupervisorctlupdate

sudosupervisorctlstartweather-station-webapp

Youmayreceivewhatlookstobeanerrormessagewhenrunningthefinalcommandhere.However,thissimplystatesthattheprocessisalreadyrunningandcansafelybeignored.

3. Finally,rebootthePitofinishthedeployment:

sudoreboot

OncethePihasrebooted,browseonceagaintotheIPaddressofthePiandyoushouldbeabletoseethesamepageasbefore.Ifso,youhavesuccessfullydeployedthewebapplicationonyourPi.

TakingreadingsfromthesensorsNowthatourappissetup,weneedtoconfigurethePitoregularlytakereadingsfromthesensorsandupdatethedatabasewiththelatestweatherconditions.Todothis,wewilluseaPythonscriptthatwillcommunicatewiththeDHT11/22andBMP180sensorsusingtheirAdafruitlibrariesandtheMaplinsensorsusingthepySeriallibraryandperformthefollowingsteps:

1. WemustfirstinstallthepySeriallibrarytobeusedbythescript.AlltheotherlibrariesusedareeitherinstalledbydefaultorwereinstalledwhenwehadsetuptheDHT11/22andBMP130sensors:

sudopipinstallpyserial

2. Next,wewillmodifytherc.localfiletoperformthescriptrunwhenthePiboots:

sudonano/etc/rc.local

3. Here,addthefollowinglinetothefile:

python/home/pi/sensor_manager.py--database

/home/pi/weather_station_webapp/weather.db--poll-interval10--submit-

interval600&

Theoutputshouldlookasshowninthefollowingscreenshot:

NoteTheintervalatwhichthescripttakesreadingsfromthesensorsandstorestheminthedatabasecanbeconfiguredbychangingthe--poll-intervaland--submit-intervalarguments.Notethatifthe--submit-intervalsettingissetanylowerthan300seconds(5minutes),thenthiscanmakethehistoryviewinthewebapplicationslowtoload.

4. Finally,rebootthePiandtrytoaccessthewebinterfacetocheckwhetherthedata

updateafterthesubmitintervalhaselapsed.

AssemblingtheweatherstationNowthatourweatherstationissetupandtakesthereadingscorrectly,it’stimetoassembletheweatherstationandsetitupoutside.

Beforewedothis,youmaywanttoconsiderhowthePiwillconnecttoyournetworkandreceivepower.Here,IwouldrecommendyouuseWi-Fifornetworking.ThiscanbesetupbyfollowingthesameprocedurethatweusedinChapter2,PortableSpeakerSystem.Forpower,Iuseda10footmicroUSBcable,whichwaslongenoughtoreachasfaroutsideasIhadlocatedtheweatherstation.

FortheMaplinweathersensors,simplyassemblethetwomastsandfixboththeanemometerandwinddirectionsensoratthetopoftheirownmastsbyusinga30mmM3screw.Thesemastscanthenbepushedrelativelyeasilyintothesoil.Sincetheyarenotparticularlytall,itisbettertoplacetheminanareaasopenaspossibletoimprovetheaccuracyofthereadingstakenfromthem.

Asanenclosurefortheremainingsensors,theArduino,andthePi,theeasiestthingtouseisaTupperware(orsandwich)box.Thisshouldbeatleast6incheswideby4inchesdeep,around3inchestall,andeitherclearorverylightlytranslucent,sothatthelightintensitydoesnotfalltoomuchbetweentheoutsideandinsideofthebox(asthelightsensorwillbemountedontheinside).

Thereareafewmodificationsthatmustfirstbemadetotheboxtomakeitsuitableforuseasanenclosurefortheweathersensors.Firstly,theremustbesomewaytomaintaintheairflowthroughtheboxtoensurethattheDHT11/22andBMP180sensorsgetaccuratereadings.Thiscanbedoneeasilybydrillingapatternofsixholesoneithersideofacornerofthebox,asshowninthefollowingimage.ThisprovidesapathforairtoflowthroughthecornerofthecasewithoutallowingmoistureandwatertogettothePiandArduino(whichwillbelocatedattheoppositeendofthebox).

Thenextthingwewillneedisawaytoruncablesinsidethebox.Thiscanbedonebyremovingthelipononesideofthebox,sothatwhenthelidisreplaced,thereisagaplargeenoughtorunthewiresthrough.Thelipcanberemovedbyusingapairofwire/sidecutterstocreateagapwideenoughforthecablesfromtheraingauge,winddirectionsensor,andamicroUSBcable,asshowninthefollowingimage:

NoteBeverycarefulwhilecuttingawaythelipoftheboxlikethis.Usingtoomuchforceortryingtocutawaytoomuchatoncecancausepartsoftheboxtochipawayathighspeed.Eyeprotectiongearshouldbewornwhiledoingthis.

Next,weneedtoassembletheelectronicsandsensorsinthebox.TheonlyrequirementhereisthattheLCDfacesdirectlyupwardsandthattheDHT11/22andBMP180sensorsareclosetothepathofairwhichgoesthroughthecorneroftheboxwheretheholesweredrilled.

Youshoulduseanadhesiveorgluetokeeptheelectronicsfrommoving.Youcanuseanythingfromatemporaryfixing,suchasBlu-Tack,toamorepermanent(butstillremovable)adhesive,suchashotglue.Whicheveryoudecidetouse,itisimportanttokeepadhesivesawayfromsensitiveareasoftheelectronics,suchasthemetallicsensorchipontheBMP180PCBorthesurfacemountcomponentsonthebackofthePi.

Thefollowingimageshowstheassembledelectronicsandsensorsinthebox:

Finally,allthatislefttodoistoreplacetheboxlid,setuptheweatherstationoutside,andapplypower.Wecannowmoveontotesttheweatherstationandlookatsomedatafromit.

Notethatwhileinstallingthewinddirectionsensor,itisimportanttoalightitproperlywiththenorthdirection.Itmustbeinstalledsuchthatwhenthearmisinposition,asshowninthefollowingimage,thevanemustpointtonorthandtheroundpointoppositethevanemustpointtosouth:

UsingthewebapplicationWhenyoufirstbrowsetotheIPaddressofthePi,youaregreetedbyapagethatwilllooksimilartothefollowingscreenshot.Thisshowsthecurrentweatherconditionsthathavebeenrecordedoverthelastmeasurementperiod(thatis,theperiodspecifiedbythe--submit-intervalparametertothesensor_manager.pyscript).

ByclickingontheHistorylinkinthetop-rightcornerofthepage,youareabletobrowsethroughalltherecordingsthathavebeentakenbytheweatherstation.

Bydefault,itdisplaysthehistoryforthepreviousweek.Thiscanbechangedbyusingthetwooptionsatthetopofthepage(notethattheseoptionsmayonlyrendercorrectlyinChrome,Opera,orSafariwebbrowsers).

Youcanalsochangewhichrecordedvaluesaretobedisplayedonthegraphbyusingtheselectionofcheckboxesatthetopofthepage.Notethatsomemeasurementsmaynotbesuitedtobedisplayedatthesametimeastheyhavedifferentranges,forexample,rainfallandthelightlevel.

Ifyoueverwanttotakeabackupoftheweatherdata,youcandosobytakingacopyoftheweather.dbfileinthe/home/pi/weather_station_webapp/directory.Ifyouwanttoerasealltherecordeddata,youcansimplyruntheinitializedatabasecommandagain.

Notetheunitsforthemeasurements:

Windspeed:Thisismeasuredinmilesperhour(MPH)Temperature:ThisismeasuredindegreesCelsiusHumidity:ThisismeasuredinpercentageRH(relativehumidity)Pressure:kPa(kilopascal),where1kPa=10mb(millibar)Lightlevelandrain:Arbitraryunits

SummaryInthischapter,welookedatthestepsneededtodesignanddeployaPython-basedwebapplicationonthePiusingtheFlaskframework.Thisisatechniquewewillbeusinginacoupleofchapterslaterinthebook,wherewewillcreateweb-basedcontrolpanelsandinformationdisplays.

WealsolookedatyetmorewaystointerfacedevicestothePi,bothdirectlyviatheGPIOportandbyusinganintermediatedevice;inourcase,anArduino.Wealsolookedattheadvantagesthiscanbringwithcertaintypesofsensor.

Inthenextchapter,wewillfurtherexploretheuseofsensors,aswecreateahomesecuritysystemthatconnectsseveralsensorsusingawirelessnetwork.

Chapter7.HomeSecuritySystemInthischapter,wewilllookathowtocreateasimplisticsecuritysystemthatwillbeabletomonitorbasicsecuritysensors,suchasdoorpositionsensorsandpassiveinfrared(PIR)sensors.Thesearecommonforstandardhomesecuritysystemsandsende-mailalertswhencertaincombinationsofsensorsaretriggered.

WhatyouwillneedThisisthelistoftheminimumpartsyouwillneedtocompletethisprojectbyfollowingthesamplesystemsetup,whichisdescribedinthefirstsectionofthischapter:

TheRaspberryPiAtleasttwonRF24L01modules(http://imall.iteadstudio.com/im120606002.html)AtleastoneArduinoUno0.1inchfemale-to-femalepinjumperwires0.1inchmale-to-femalepinjumperwiresAselectionofsecuritysensors:

ThePIRsensor(www.rapidonline.com/Electronic-Components/Pir-Module-61-1516)Magneticdoorsensorsorreedswitches(www.rapidonline.com/Electronic-Components/Surface-Mounting-Proximity-Switch-78-1672)

Thenumberofsensors,Arduinoboards,andRFmodulesyouwillneedforthisprojectwillgreatlydependonhowmanyroomsyouwantthesecuritysystemtocoverandhowmanysensorswillbeusedineachroom.Inthischapter,itwouldbeworthreadingatleastthesectiononhowtodesignyoursecuritysystembeforeyouorderanyparts.Dothistoensurethatyouhaveenoughrequirementstobuildasystemthatwillworkwellforyourscenario.

ThesecuritysystemstructureThesecuritysystemwillbedividedintofivemainparts:theArduinosensornodes,theRFnetworkthatconnectseachnodetotheRaspberryPi,theMQTTbrokerthatconnectstheRFnetworktothewebapplication,thewebapplicationthatmanagesthesenoreventsandalerts,andthedatabasethatstorestheconfigurationofthesensorsandalarmsandthehistoryofeachsensor.

EachsensornodeiscomprisedofanRFmodulethatallowscommunicationbetweenthenetworkofsensornodesandseveralsecuritysensors,suchasPIRmotiondetectorsandreedswitchdoorsorwindowsensors,andboththestandardsensorsusedonthestandardhomesecuritysystems.Whilethesenodescanbebatterypoweredforbetterreliability,wewillpoweroursbyusingaUSBportandUSBpowersupply.

TheRaspberryPiwillserveasboththehostserverforthewebapplicationanddatabaseandthebasenodeintheRFnetwork.ThiswillusethesameRFmodulesandsoftwarelibrariesastheArduinosensornodes.

Oursecuritysystemwillnotuseabellorsounder,suchasaconventionalsecuritysystem;instead,itwillsende-mailalertstoanaddressconfiguredviathewebinterface.Itwillalsoallowalarmstobeconfiguredmuchmorefreelythanaconventionalsystem,allowingyoutosetseveralalarmsforeachdifferentareainahouse.Itwillalsoallowthealarmstoactindependentofeachother.

DesigningyoursecuritysystemFortherestofthechapter,wewillassumethatthesecuritysystemhasthreesensornodes;here,allthreehavemagneticdoorsensorsandonlytwooutofthreehavePIRmotionsensors.

Atthisstage,youneedtothinkaboutwhereeachnodewillbelocated,astheRFmodulescanonlytransmitoveracertaindistancebeforethesignaleitherbecomestooweaktoensurereliablecommunicationorislostcompletely.Frommyowntesting,Ihavefoundthatthelinkbetweentwonodescanrarelytravelmorethanonewallorfloor.

Therefore,inordertohavealongerdistancebetweenthebasenodeandsensornode,thesensornodemustcommunicatethroughanodethatactsasarepeater.Thisishandledbythenetworkprotocollibraryusedonthesensor’snodesandthePi.Wewilllookatthisinmoredetaillaterinthischapter,butfornow,provisioningatleastonesensornodeineachroomyouwanttohaveasensorinaswellasanyroombetweennodeswillbesufficient.

Thefollowingdiagramroughlyshowsthestructureofthesystemwewillusefortherestofthechapter:

Ifyouareusingyourownsystemdesign,thenithelpstomakeyourowndiagramsimilartothis.Makesuretonotethesensornodeaddress,location,andMQTTtopicofeachsensortohelpmaketheprogrammingofeachofthesesensornodesandtheadditionofthesensorstothewebapplicationeasier.

WebapplicationsThesecuritysystemwillbebasedonawebapplicationthatwillbeusedtorecordandvieweventsfromthesensorsandwillallowaconfigurationofsensorsandalarms.

Forthis,wewillusetheFlaskframeworkforPython,whichwasusedinthepreviouschapter,andtheMQTTprotocoltoestablishcommunicationbetweenthesensorsandwebapplication.Thisprotocolisapublisherandsubscribermodel,whereclientscansubscribetoinformation(topics)theyareinterestedinandreceivenewdataasitismadeavailable(published)byotherclients.

Anoverviewofthestructureofthewebapplicationisshowninthefollowingdiagram.Aswedidinthepreviouschapter,wewillusetheSQLitedatabaseengine:

DeployingourapplicationWewillfirststartbydeployingthewebapplicationonthePi.Thiswillmostlybethesameprocessaswasusedinthepreviouschapterfortheweatherstationwebapplication.However,thereareadditionalstepshereasthesecurityapplicationrequiresanextraconfigurationfiletosetoptionsforthelogindetails,MQTTbroker,ande-mailalerts:

1. First,wewilladdanadditionalsourcetothelistofrepositoriesthatAPTsearchesfor.Whenweinstallnewpackages,thiswillallowustoinstalltheup-to-dateversionoftheMosquittoMQTTbrokerneededforthesecuritysystem:

wgethttp://repo.mosquitto.org/debian/mosquitto-repo.gpg.key

sudoapt-keyaddmosquitto-repo.gpg.key

cd/etc/apt/sources.list.d/

sudowgethttp://repo.mosquitto.org/debian/mosquitto-wheezy.list

cd

2. Nowthattherepositoryhasbeenadded,weneedtoupdatethelocalcopyofthelistofpackagesthatareavailableandinstallanyupdateswhileweareatit:

sudoapt-getupdate

sudoapt-getupgrade

3. NowthatthePiisuptodate,wecanstartinstallingthepackageswewillneedforthesecuritysystem.Don’tworryifyougetamessagesayingapackageisalreadyinstalledorisuptodate,assomeofthesemayormaynotbealreadyinstalled:

sudoapt-getinstallmosquittomosquitto-clientspython-pipgitpython-

devgunicornsupervisornginx

sudopipinstallpaho-mqtt

4. Fromhereon,theprocedurewillbesimilartothatusedwhileinstallingFlashinthepreviouschapter.However,wewillbemakingacoupleofmodificationsthistime,sowewillgothroughthefullprocedurehere.ContinuebycloningtheFlashcoderepositoryandinstallFlaskonthePi:

gitclonehttps://github.com/mitsuhiko/flask.git

cdflask

sudopythonsetup.pyinstall

5. Next,weneedtocopytheNginxconfigurationfilesforthesecuritywebapplicationsite.EnablethesiteconfigurationandremovethedefaultNginxsite:

sudocpconfig_files/nginx/security.conf/etc/nginx/sites-

available/security.conf

sudoln-s/etc/nginx/sites-available/security.conf/etc/nginx/sites-

enabled/

sudorm/etc/nginx/sites-enabled/default

6. Now,wecanletNginxtesttheconfigurationandassumingthatthetesthaspassed,restarttheservice.Ifthetestfailed,gobacktotheconfigurationandensurethatallthefileshavebeencopiedcorrectly:

sudonginx-t

sudoservicenginxrestart

7. Next,wecantestthewebapplicationbyrunningitmanuallywithGunicorn.Here,itisnotimportantthattheapplicationismissingtheconfigurationfile,soitcanbestartedwiththefollowingcommands:

cd~/security_webapp

flask--app=securityinitdb

gunicorn-b127.0.0.1:5000security:app

NoteNotethatwhileinitializingthedatabase,youmaygetanerrorsimilartothatshowninthefollowingscreenshot;thisiscausedbytheexitoftheapplicationwhiletheMQTTclientisstillrunningandcanbesafelyignored.

8. Now,browsetheIPaddressofthePionacomputerofthesamenetworkandyoushouldseeapagesimilartothatshowninthefollowingscreenshot.Asitis,thisistheonlypageofthesitethatwillwork,astheapplicationisrunningwithouttheconfigurationfile:

Ifthewebpagedoesnotappear,thenyoumayneedtorebootthePibeforetrying

againtoflushoutanybadconfiguration,whichmaystillbeappliedtooneoftherunningservices.Ifthisdoesnotwork,thengobacktotheconfigurationstepsandensurethateachfilewascopiedcorrectly.

9. Next,wewillconfigurethewebapplicationthatwillstartautomaticallywhenthePibootsusingthesupervisor:

sudocpconfig_files/supervisor/security-webapp.conf

/etc/supervisor/conf.d/security-webapp.conf

sudosupervisorctlreread

sudosupervisorctlupdate

sudosupervisorctlstartsecurity_webappp

NoteHere,youcantrytoaccessthewebapplicationagain.Thisshouldgivethesameloginpageasbefore.Thiswillstillbetheonlyfunctionalpageintheapplicationatthispoint.

10. Nowthatthewebapplicationisdeployed,weneedtoedittheconfigurationfiletoenablelogin,MQTTbrokerconnection,ande-mailalerts:

sudosupervisorctlstopsecurity_webappp

sudocpconfig_files/security.conf~

nano~/security.conf

11. Now,weneedtomodifytheconfigurationfilesothatitsuitsthesetupwehavefortheMQTTbroker,e-mailalerts,andthecredentialsusedtologintothewebapplication.Here,wemustalsosetasecretkeythatallowsourapplicationtosaveinformationinabrowsersession.

Intheconfigurationfile,youwillfindthatalltheconfigurationentriesarealreadythere;theysimplyneedtobepopulatedwithcustomizedvalues.NotethatwhiletheSECRET_KEYvaluewillallowyoutologintotheapplication,itshouldbechangedtosomethinguniquetoyourapplicationbeforeyoustartusingthesystemproperly.

TheMQTT_BROKERandMQTT_PORTconfigurationparametersareusedtodeterminewhichMQTTbrokertheapplicationshouldconnectto.Here,weareusingthebrokerrunningonthePilocally,sothesecanbeleftastheparameters’defaultvalues.

TheUSERNAMEandPASSWORDparametersareusedtosetthecredentialsthatyouwilluseontheloginpagetoaccessthewebapplication.Asitis,thewebapplicationonlysupportsasingleuser.

TheSMTP_SERVER,SMTP_USERNAME,SMTP_PASSWORD,andFROM_EMAILparametersareusedtoconfigurethesendingofe-mailalerts.Currently,onlyGmailandGoogleAppse-mailaccountshavebeentestedwiththeapplication,soitishighlyrecommendedthatyouuseoneoftheseaccounts.However,thePythonSMTPlibrary(https://docs.python.org/2/library/smtplib.html)iswelldocumented,somodifyingthesend_mail()functioninsecurity.pyisalwaysanoptionifyouwanttouseadifferente-mailprovider.

AssumingthatyouwilljustuseaGmail(orGoogleApps)e-mailaccountfore-mailalerts,theSMTP_SERVERparameterisalreadysettothecorrectvalue.SMTP_USERNAMEandSMTP_PASSWORDmustbesettoyouraccountlogindetails,whichareyourfulle-mailaddressandpassword.TheFROM_EMAILparameterisusedtosetthee-mailaddressthemessageissentfrom;thisshouldbesettothesameastheSMTP_USERNAMEparameter.

Oncetheconfigurationfileiscomplete,itshouldlooksomethinglikewhatisshowninthefollowingscreenshot:

Nowthattheconfigurationfilehasbeenmodified,thelaststepistostartthewebapplicationoncemore:

sudosupervisorctlstartsecurity_webappp

Oncethisfinalstepiscomplete,youcantrytoaccessthewebapplicationbybrowsingtotheIPaddressofthePionacomputeronthesamenetwork.Thisshouldpresentyouwiththesameloginscreenasbefore.

ConfiguringsensorsandalarmsNowthatthewebapplicationisdeployedcorrectly,itistimetologintoitandconfigurethesensorsandalarmswewilluseforthesystem:

1. StartbybrowsingtotheIPaddressofyourPiandenterthelogindetailsinthepageyouaretakento.Theselogincredentialsaretheonesthatwereconfiguredintheconfigurationfileintheprevioussection.

2. Onceloggedin,youwillbegreetedwiththeSensorspage.Thisshowsalistofallthesensorsthatarecurrentlyconfiguredonthesecuritysystem.WewillstartbyfirstaddinganewsensorbyclickingontheAddNewSensorlinkatthetopofthepage.

3. Here,wearegivenoptionsforthenameandidentificationofthesensor,bothinrelationtothepositioninthehouseandtheMQTTtopicthatitmapsto.Wewillsetthissensortobethedoorsensoronthefirstsensornode.Forallthesensorswewilluse,thevalueofTriggeredtextshouldbe1.

4. Oncethisiscomplete,clickonAddandyouwillseeamessagesayingthatthesensorhasbeenadded.Atthebottomofthisscreen,youwillseeasectionthatdisplaysthelastrecordedeventforthissensor.Sinceithasjustbeenadded,noeventshavebeenrecordedyet.

5. Followthisprocedurefortheremainingsensorsinyoursetup,followingthesystemstructurediagramyoumadeearlierinthischapter.Oncethisiscomplete,youwillhaveafairfewsensorsaddedtothesystem,asdepictedinthefollowingscreenshot:

6. Next,wewillmoveontoaddanalarmforsomeofthesensors.Thiswillcontrolhow

andwhenyoureceivealertswhenthestateofthesensorsinthenetworkchanges.Tostart,clickonAlarmstonavigatetothealertspageandaddanewalarm.

7. Onthisscreen,youwillbegiventheoptiontogivethealarmanameanddescriptiontoassistidentificationaswellasafieldforane-mailaddresstosendnotificatione-mailswhenthealarmistriggered.

8. Atthebottomofthescreenisalistofallthesensorsthathavebeenaddedtothesecuritysystem.Checkallofthemthatyouwanttohaveaneffectonthisalarm.

9. Next,choosethealarmtypefromtheAlertWhendrop-downbox.Thiscontainsseveraloptionsforhowsensorsmustbehaveinordertotriggerthealarm.Typically,youwillusuallysetthistoAnyOneTriggered.Thereisalsoanoptiontodisablethealarmifneeded.

Atthispoint,thesystemissufficientlyconfiguredtobehaveasasimplesecuritysystemandsendalertswhensensorshavebeentriggered.However,shouldyoueverneedtolookupthehistoryofasensortoseewhenithasbeentriggered,thereisaneventspage,whichwilldisplayalltherecordedsensoreventsandthetimetheywererecordedat.

Thiscanalsobehandytoverifythatasensorisfunctioningcorrectly.

Asweareyettoaddanysensorstothesystem,youcansimulatethetriggeredsensorsusingtheMosquittocommand-linetools.Ifnotalreadyinstalled,theycanbedownloadedusingthefollowingcommand:

sudoapt-getinstallmosquitto_clients

Oncetheseareinstalled,youcansimulate,forinstance,adoorbeingopenedandclosedusingthefollowingtwocommands,wherePI_IPistheIPaddressofthePi:

mosquitto_pub-h192.168.0.17-tdoor2-m1

mosquitto_pub-h192.168.0.17-tdoor2-m0

OntheEventspageofthewebapplication,thiswillappear,asshowninthefollowingscreenshot:

Whenanalarmistriggeredandavalide-mailaddresshasbeensetintheconfigurationpage,ane-mailsimilartothefollowingwillbedeliveredtotheconfigurede-mailaddress:

InterfacingsensorsThetwosensorswewilluseinthisprojectarefairlysimpletointerfacewithArduino,asbothuseasimpledigitalsignal.WewillnowlookattheelectricalconnectionbetweenthesensorsandArduinoandtheconfigurationrequiredintheArduinocodeforeachsensor.

Inthecodeforthesensornodes(therf_network/SensorNode_Arduinodirectory),therearetwoimportantvariablesrelatedtotheconfigurationofsensorsonagivennode:NUM_SENSORSandsensors.Thefirstisacountofhowmanysensorsareattachedtothecurrentsensornodeandthesecondisanarrayofconfigurationsforeachsensor.

Theconfigurationforeachsensorisstoredinastructwiththefollowinginitialization:

{"MQTT_TOPIC",PIN,ACTIVE_LOW,PULL_UP}

Here,MQTT_TOPICistheMQTTtopicwherethechangestothestateofthesensorwillbepublished,PINistheArduinoIOpinthesensorisconnectedto,andACTIVE_LOWshowswhetherthesensorshouldbeconsideredastriggeredwhentheinputislow.Ifthisisthecase,thisshouldbesetto1,otherwise0.PULL_UPdictateswhethertheinternalpullupresistorshouldbeactivatedforthesensor;ifso,thisshouldbesetto1,otherwise0.

ThePIRmotionsensorsThePIRmotionsensorshavethreewires:ground,power,andsignal,wherethesignaloutputishighwhenmotionisdetectedinthefieldofviewofthesensor.

Thesesensorsoperatebydetectingarelativechangeintemperatureacrossthefieldofviewofthesensor.Thisisdonebypositioningthetwoinfrareddetectorsatslightlydifferentanglesfromthelens.Whenatemperaturechangeoccurs,thevoltageacrossthetwosensorsrelativetoeachotherchanges,whichisthenprocessedonthesensorthatistobeconvertedintoadigitaloutput.

Ifyoulookfromthetopofthesensor(thatis,withthelensfacingtowardsyou),thethreewiresareground,power,andsignalfromlefttoright.Thesignalwireisindicatedwithagreystripealongit.

TowirethisuptoArduino,connectthegroundwiretoanArduinopinmarkedGND,sendpowertoeithertheArduinopinmarkedas+5VorVinandthesignalwiretoanyunuseddigitalinput(any,from2to8).

NoteNotethatifyouplantopowertheArduinosensornodeusingapowersupplyhigherthen5V,thenyoushouldconnectthePIRsensorspowerwireto+5VandnotVin.Supplyingthesensorwithmorethan5VmaycausepermanentdamagetoArduinoorthepower

supply.

WithintheArduinocode,aPIRsensorshouldbeaddedwiththevalueofACTIVE_LOWandPULL_UPsetto0.

MagneticdoorsensorsThissensorcanbeusedtodeterminewhentwoobjects,commonlyadooranditsframe,moveapart.Thisissimplyareedswitchandmagnet,thereforeallthatisrequiredtousethissensoristodetectwhenadigitalinputsignallevelchanges.

Althoughtherearefourwirescomingfromthesensor,onlytwoareneededforourusage.Thesetwohavetheendsofthewirestripped,revealingasectionoftheconductor,andareslightlylongerthantheothertwo.Thetwounnecessarywirescanbecutoffifdesired.

WithintheArduinocode,amagneticdoorsensorshouldbeaddedwiththevalueofACTIVE_LOWsetto0andPULL_UPsetto1.

TheRFnetworkTheRFnetworkthatwillbeusedforthesensornodesisprovidedbytheRF24Networklibrary(https://github.com/TMRh20/RF24Network).ThisallowsRNnodestobenetworkedinatreestructureinwhicheachnodecanhaveuptofivechildnodes,sinceeachindividualnodecanlistentouptosixothernodesatonce.

Assuch,theaddressesforthenodesareoctalandfollowthestructure,asshowninthefollowingdiagram,where000isalwaysthebasenode,001isachildofthebasenode,021isachildnodeof001,andsoon:

Thisallowsamessagetobepassedtoanynodeonthenetworkbyfirsttransmittingitupwardsthroughthetreeuntilitreachesthefirstnodethatisacommonpathforboththesendingandreceivingnode.

SettinguptheRaspberryPiTosetupthePiasthebasenodefortheRFnetwork,wemustfirstconnecttheRFmoduletotheGPIOportandinstallthedriversthatwillallowustoreceivemessagessendtoitbyusingaPythonscript.Todothis,performthefollowingsteps:

1. First,startbywiringthemoduletotheGPIOportusingthefollowingwiringdiagram:

2. Next,installthedriverfortheRFmodule.Thisisthedriverthatallowsbasicpoint-to-pointcommunicationusingtheRFmodules:

sudoapt-getinstalllibboost-python-devgit

gitclonehttps://github.com/TMRh20/RF24.git

cdRF24

sudomakeinstall

cdRPi/pyRF24

sudopythonsetup.pyinstall

3. Nowthatthedriverisinstalled,returntothehomedirectory:

cd

4. Next,wewillinstalltheRFnetworkdriver.Thisisthenetworklayerthatprovidesthetreenetworkrouting:

gitclonehttps://github.com/TMRh20/RF24Network.gitRFNetwork2

mvRFNetwork2/RPi/RFNetwork~

cdRFNetwork

sudomakeinstall

cdRF24Network2/RPi/pyRF24Network

sudopythonsetup.pyinstall

5. Oncethetwolibrariesareinstalled,youwillneedtocopytheBaseNode_RPi.pyscriptfromtherf_networkdirectoryinthefilesforthisprojecttothehomedirectoryonthePi.

6. Nowthatthedriversforboththemoduleandthenetworklayerareinstalled,wecan

testthebasenodescriptusingthefollowingcommand:

sudopythonBaseNode_RPi.pylocalhost1338

Thisshouldgiveanoutputsimilartothefollowing.Ifyouseearepeatingpatternintheconfigurationdataorallthebitsaresettothesamevalue,thenyoumayhaveanissuewiththewiringbetweentheRFmoduleandthePi.

Assumingthattheoutputofthescriptwassimilartothepreviousscreenshot(suchthatthevaluesarenotall0x00or0xFF),wecangoaheadandconfigurethebasenodescripttostartwhenthePiboots.Todoso,performthefollowingsteps:

1. Opentherc.localfileinnano:

sudonano/etc/rc.local

2. Addthefollowinglinetotheendofthefile,justbeforetheexit0line:

python/home/pi/BaseNode_RPi.pylocalhost1883

Thisisshowninthefollowingscreenshot:

Oncethisiscomplete,rebootthePitorunthebasenodeandwebapplicationonboot.ThiscompletestheconfigurationthatneedstobedoneonthePi.

SettingupArduinoIt’snowtimetoprogrameachoftheRFnodesthatwillbeusedinthesensornetwork.Wecanprogramtheseusingthecodeintherf_network/SensorNode_ArduinodirectoryinthefilesforthisprojectandtheArduinoIDE.

YoushouldalreadyhavetheArduinoIDEinstalledfromwhenitwasusedinapreviouschapter.However,wefirstneedtodownloadsomeadditionallibrariesfortheRFmodule:

1. Thetwolibrariesneededcanbedownloadedfromhttps://github.com/TMRh20/RF24andhttps://github.com/TMRh20/RF24Network.YouwillseetheDownloadZIPoptionattheright-handsidebarofthewebsite.

2. Oncethesearedownloaded,extractboththearchivesandplacethemintothesketchbook/librariesdirectory.ThesketchbookdirectoryiswheretheArduinoIDEstoressavedcodefilesbydefaultandwhereitsearchesforthird-partylibraries.Bydefault,thisfolderisinyourhomedirectory.

Whendoingthis,ensurethattheprogramusedtounzipthearchivesdoesnotcreateanadditionaldirectory(thisisknowntohappenwhenyouunzipthemwithWindowsExplorer).Thedirectorystructureshouldbesimilartothatshowninthefollowingscreenshot:

3. Next,wewillconnectanRFmoduletoeachArduinothatwewilluseasasensornode.ThisshouldbedonebyfollowingthenextdiagramandwhentheArduinoisnotpowered:

Next,usingthefollowingsteps,programeachArduinobyusingthesensornodecodebasedonthesystemstructurediagramgivenearlierinthischapter:

1. ConnecttheArduinotoyourPCandopenanunmodifiedversionoftheSensorNode_Arduino.inocodeintheArduinoIDE.

2. ChangetheTHIS_NODE_ADDRvariabletotheaddressofthenodeyouhaveconnected.Notethathaving0atthestartoftheaddressisrequired,thatis,iftheaddressis23,youmustuse023asthevalue.

3. SettheNUM_SENSORSandsensorsvariablesasdescribedintheInterfacingsensorssection.

4. Ifyouprogramthenodesinorderoftheirpositionawayfromthebasenode(forexample,002,012,and003),youwillbeabletotesteachnodeasyouprogramit.Thisisassimpleasopeningtheeventspageonthewebapplicationandverifyingthatneweventsshowupforthesensorwhenitischanged.Ifthisdoesnothappen,refertotheTroubleshootingsection.

5. Assumingthatthesensornodeworksasintended,youcannowdisconnectthenodefromyourPC.Although,ifyouwishtokeeptestingadditionalnodes,youwillneedtopowerthenodeexternally.

Onceallthesensornodesareprogrammedandtested,theycanbeinstalledintheirintendedpositions.IfoundthatBlu-Tackisagoodtemporaryfixforthenodesthatareto

beplacedabovethedoors.

ThesensornodewithadoorswitchandPIRsensorinstalledaboveadoorframeusingBlu-Tack

TroubleshootingIfyoufindthatasensornodeisnotupdatingthesecuritywebapplicationwhenthesensorsaretriggered,youmayneedtofirstcheckthewiringandconfigurationofthesensornode.Dothistocheckwhetherthesensornodehasavalidaddressandthatitistryingtoconnecttoaparentnodethatexistsonyournetwork(refertothestartofTheRFnetworksection).

Ifthisdoesnotseemtobetheissue,thenyoumaysimplybeoutofrangeofthesensorsorhaveasignalintegrityissuecausedbyotherdevicesusingthesamefrequencyrange.Ifyoususpectthistobethecase,youcantrychangingthevalueoftheCHANNELvariablesintheBaseNode_rPi.pyandSensorNode_Arduino.inocodefiles.ThisvaluesetsthefrequencythattheRFmoduleoperateson.Thefrequencycanbederivedbyf=2400+CHANNELMHz.

Hence,thedefaultvalueof90givesafrequencyof2.49GHz.TheRFmodulecanoperateanywherebetween2.4GHzand2.525GHz.

SummaryInthischapter,wegainedmoreexperiencewithexpandingthePi’shardwarecapabilitybyaddingadditionalmeansofcommunicationtoitandaddinghardwareusinganewprotocol,thatis,SPI.

ArduinoalsoplayedalargepartinthischapterandhashelpedtoprovideanexampleofawiderangeofhardwarethatcouldpossiblybeusedwiththePi.Evenifasensor,motor,orotherdevicecannotbecontrolleddirectlyfromthePi,itisalmostguaranteedthatthereisanadditionalpieceofhardwarethatcansitbetweenthePiandthedeviceandallowcontrolofthedevicefromthePi.

Wealsohadamorein-depthlookatthetypeofwebapplicationsthatcanbecreatedusingPythonandFlaskandintroducedquiteafewnewfeaturesintothesecuritywebapplicationovertheapplicationmadeinthepreviouschapter.

WewillcontinuetoexplorethewaywebapplicationscanbeusedasaninputmethodforthePiandcontrolphysicalhardwareinthelaterchaptersinthisbookbyusingseveralnewwaysofinterfacingcustomelectronics.

Chapter8.Remote-operatedRoboticArmInthischapter,wewillusetheRaspberryPitocreateasimpleroboticarmactuatedwithseveralmicroservosmountedonamovablebaseusingtwomotors.AllofthesewillbecontrolledthroughawebinterfaceviathePiGPIOport.

Wewillalsomountthecameramoduleatthefrontofthebaseandstreamittothewebinterface,enablingafullremoteoperation.

WhatyouwillneedThisisalistofthepartsthatyouwillneedtocompletethisproject.Mostofthemwillbeavailableateitheralocalelectroniccomponentsstoreoranonlineretailer:

TheRaspberryPiA3mmMDF(600x600mm)M3andM4screws,washers,andnutsTheM3threadedbar4xmicroservos(www.amazon.co.uk/Vktech-MG90S-Geared-Helicopter-Airplane/dp/B00FF26480)Servoextensioncables(www.amazon.co.uk/300mm-Servo-Extension-Cable-Futaba/dp/B009REWWGU)Arelayboard(www.ebay.co.uk/itm/New-8-Channel-5V-Relay-Module-Board-for-Arduino-PIC-AVR-MCU-DSP-ARM-UK-/151105724470)Gearedmotors(www.rapidonline.com/Electrical-Power/950d5001-Gearbox-and-Motor-500-1-6mm-Shaft-6-15v-37-1114)0.1inchpinheaders0.1inchfemale-to-femalepinjumperwires0.1inchmale-to-femalepinjumperwiresA18AWGwireThickcopperwire(www.clasohlson.com/uk/Copper-Wire-1.2-mm/30-5028)Asmallsectionofaprototypingboard(www.maplin.co.uk/p/veroboard-copper-stripboard-100x160mm-a62rl)A9VbatteryA9Vbatteryclip(www.maplin.co.uk/p/pp3-snap-battery-clip-hf28f)AUSBpowerbank(www.maplin.co.uk/p/lithium-ion-6000mah-portable-power-bank-n48lk)The38mmversionofacastor(www.clasohlson.com/uk/Swivel-Castors/Pr309743000)AnoldUSBcableTheRaspberryPicameramodule

DriveelectronicsThefirststepistowireupandconfigurethedriveelectronicsandmotorsthatwillmovethevariouspartsoftherobotarm;thiswillconsistoffourmicroservosthatwillmovethearm,andtwogearedmotorsthatwillprovidedrivetothechassis.

Theservosarepoweredbya5Vpowersupplyandcanbedrivenusingapulseddigitalsignal(throughPulseWidthModulation(PWM))fromthePiGPIOports,whichdefinethepositionthatthearmoftheservoistobekeptin.

Themotorswillbedrivenusingarelayboard,whichallowsthePiGPIOporttoswitchthehighercurrentsneededtopowerthemotor.Thisisjustoneofthemanywaysthiscanbedone.AnotherpossibilityistouseaMOSFETH-bridge,whichwillalsoallowcontrolofthespeedofthemotors.However,therelaysolutionissimplerinbothcodeandelectronicconstruction,soitwillbeusedhere.

Thewiringforthedriveelectronicsisshowninthefollowingdiagram:

ThewiringofthePiGPIOheaderisshowningreaterdetailinthefollowingdiagram:

Wewillstartbyconstructingthepowerboard;thisissimplytwosetsof0.1inchpinheadersonasmallsectionofthestripboardthatwilldistributethe5Vandgroundpowerrails.Wewillneedatleastsevenheadersforboththe5Vandgroundrails;however,addingmoreheaderswillallowpossibleexpansionlater.

Theboardshouldbelaidoutasshowninthefollowingdiagram:

Nowthatwehaveallthepartsneededforthedriveelectronics,wecanstartassemblingthemtotestwiththewebapplication,laterinthechapter:

1. Soldera18AWGwireontoeachterminalofbothmotors,asshowninthefollowing

image:

2. Takesomemore18AWGwiresandwireuptherelayboard,asshowninthediagramearlierinthechapter.

3. ConnectthemotorsandPP3batterycliptotherelayboard.Bynow,theboardwiringshouldlooksomethinglikewhatisshowninthefollowingimage:

4. Removethesmallorangepinjumperonthethree-pinconnectionontherelayboard;itcanbestoredbyconnectingonesideofittothemiddlepinofthisheader,asshowninthefollowingimage:

5. Now,takethepowerboardandconnectthefourservostoit,asshowninthefollowingimage,toprovidethemwithpowerandleavethesignalpinaccessiblefromthesideoftheboard:

6. Next,takefourmale-to-femalepinjumpercablesandconnecttheservostotheGPIOheader,asshownintheprecedingdiagram.

7. TaketheUSBcableandcutthecable10cmawayfromtheUSBAconnector.8. Striptheouterinsulationandshieldingtorevealfourwires.9. Striptheredandblackwires.Thesearethe5Vandgroundpowerconnectionsthat

wewillusetopowertherobotarmfromtheUSBpowerbank.10. Connectthewirestothetwomale-to-femalepinjumpersusingastripoftwo

terminalblocks,asshowninthefollowingimage:

11. Finishoffanyremainingwiringbyfollowingthewiringdiagramshownearlier.

Nowthatthewiringiscomplete,attachtheUSBpowerbanktotheUSBcabletoprovidepowertothePiandservos.Ensurethatyouusethehigheroutputcurrentportonthebank(usuallymarkedaseither2.1Aorusedfortabletcharging)andconnecta9VPP3batterytothebatteryclipattachedtotherelayboard.

SettingupthecameraThereareafewwaysinwhichwecouldstreamavideofromtheRaspberryPicameramoduletoawebpage.TheeasiestofwhichistousetheVideoforLinux2(V4L2)driver(whichisdocumentedingreaterdetailatwww.linux-projects.org/modules/sections/index.php?op=viewarticle&artid=14),whichincludesaserverthatallowsthecameratobecontrolledandstreamedoveranetworkconnection.

First,wewillconnectandconfigurethecameraintheRaspbianOSandperformthefollowingsteps:

1. Withthepowerdisconnected,connectthecameramoduletotheCameraSerialInterface(CSI)portonthePijustbehindtheEthernetport.Youcandothisbyliftingthecableclip,insertingtheflat,flexcable,asshowninthenextimage,andpressingdownontheclipsuchthatthecableisfirmlyheldinplace:

2. Next,bootintoRaspbianandruntheconfigurationutility:

sudoraspi-config

3. SelecttheEnableCameraoptionusingthearrowkeysandpressEnter:

4. SelecttheEnableoptionandpressEnter:

5. ExittheconfigurationutilitybyselectingtheFinishoptionandrebootthePi.

ThePicameraisnowenabledwithintheOS.WewillnowinstalltheV4L2driverwiththefollowingsteps:

1. Beforeinstallingthedriver,wefirstneedtoaddanadditionalrepositorytotheAPTpackagemanager.ThismanagerrequiresyoutodownloadandaddanAPTkey,whichisdoneusingthefollowingtwocommands:

wgethttp://www.linux-projects.org/listing/uv4l_repo/lrkey.asc

sudoapt-keyadd./lrkey.asc

2. Next,wemustaddtherepositorytothelistofsourcesusedbyAPT.Thisisdonebyeditingthesources.listfileusingnano:

sudonano/etc/apt/sources.list

3. Next,addthefollowinglinetothesources.listfile:

debhttp://www.linux-projects.org/listing/uv4l_repo/raspbian/wheezy

main

Thislookssimilartowhatisshowninthefollowingscreenshot:

4. Now,weneedtorefreshthelistofpackagesknowntoAPTandfinishbyinstallingtherequiredpackages:

sudoapt-getupdate

sudoapt-getinstalluv4luv4l-raspicamuv4l-raspicam-extrasuv4l-

server

5. Oncetheinstallationiscomplete,rebootthePitocompletethesetup.

Nowthatthecameramoduleandstreamingserverarebothsetup,thecameracanbetestedbybrowsingtheIPaddressofthePiontheport8080usingaPCconnectedtothesamenetworkasthePi.Thisisdonebyentering,forexample,192.168.0.56:8080intothebrowseraddressbarassumingthat192.168.0.56wastheIPaddressofthePi.

Assumingthattheserversetupwentaccordingtoyourplan,youshouldseeawebpagesimilartothatshowninthefollowingscreenshot.Here,youwillseetwolinks:onetoviewthevideostreamfromthePicameraandonetoconfigurethecamerasettings.

Althoughwewillbeabletoviewastreamstraightaway,wewillgotothesettingspagefirst(showninthefollowingscreenshot)inordertochangethecaptureresolutiontoincreasetheframerateofthevideostream.

Here,wewillchangetheimagewidthandheightoptionsatthetopofthepage.Theoptimalvalueswilldependonthenetworkconnectionbeingused.However,Ihavefoundthat600x400isareasonablestartingpoint,asthisstreamswellonmostconnectionsandgivesanimageofsufficientqualityforwhichwewillusethecamera.

Tosetthis,enterthecorrespondingoptionsintheheightandwidthfieldsatthetopofthepageandclickontheApplybuttontowardstheendofthepageasshowninthefollowingscreenshot.Oncethisisapplied,youwillberedirectedbacktothesettingspage.Togetbacktothemainpage,eitherusethehomelinkatthebottomofthepageornavigatetothepagemanuallybyusingthesameaddressweusedpreviously.

Onceyou’rebackonthemainpage,selectthevideostreamlinktoviewthelivefeedfromthePicamera.Thefollowingscreenshotdisplaysthemainpageonwhichthevideoisstreamed:

Youwillnoticesomedelaybetweenthemovementinthefrontofthecameraanditbeingdisplayedonthewebpage.ThisiscausedbyoverheadsinthestreamingprotocolandthenetworkthePiandcomputerareconnectedto.Unfortunately,thereislittlethatcanbedoneaboutthis,however,Ihaveonlyevermanagedtomeasureatmostthreesecondsofdelay.

DeployingwebapplicationsNext,wewilldeploythewebapplicationthatwillallowustocontrolthearmandchassisremotelyandviewthevideostreamfromthePicamera.SincethiswebapplicationisalsobuiltusingtheFlaskframework,theprocessofdeployingitwillagainbesimilartothatusedinthepreviouschapters.

Beforewestart,besuretocopytheconfig_filesandrobot_arm_webappdirectoriesfromtheprojectfilestothe/home/pidirectoryonthePi:

1. First,wewillinstalltherequiredpackagesandlibraries,includingtheRPIOPythonlibraryusedtocontroltheGPIOpinsfromPython:

sudoapt-getupdate

sudoapt-getupgrade

sudoapt-getinstallpython-pipgitpython-devgunicornsupervisor

nginx

sudopipinstallRPIO

2. Next,downloadandinstalltheFlaskframework:

gitclonehttps://github.com/mitsuhiko/flask.git

cdflask

sudopythonsetup.pyinstall

cd

3. Now,copytheNginxconfigurationandperformtheconfigurationself-test:

sudocpconfig_files/nginx/robot_arm.conf/etc/nginx/sites-

available/robot_arm.conf

sudoln-s/etc/nginx/sites-available/robot_arm.conf/etc/nginx/sites-

enabled/

sudorm/etc/nginx/sites-enabled/default

sudonginx-t

sudoservicenginxrestart

4. Copythesupervisorconfigurationandtellthesupervisortorereadtheconfigurationfiles:

sudocpconfig_files/supervisor/robot_arm_webapp.conf

/etc/supervisor/conf.d/robot_arm_webapp.conf

sudosupervisorctlreread

5. Copythewebapplicationconfigurationfiletothehomedirectory.ThisdefinesthecalibrationsettingsfortheservopositionsandtheGPIOpinseachdeviceisconnectedto.TheGPIOsettingsshouldnotbechangediftheelectronicswerebuiltbyfollowingthewiringdiagram.Wewilllookatthecalibrationvaluesingreaterdetaillaterinthischapter.However,itwouldbeusefultoopenthefileandbefamiliarwiththeoptionsthatareavailablethere.

sudocpconfig_files/robot_arm.conf~

nano~/robot_arm.conf

6. Finally,tellthesupervisortostartthewebapplication:

sudosupervisorctlupdate

sudosupervisorctlstartrobot_arm_webappp

Nowthatthewebapplicationhasbeendeployed,wecantesttheelectronicsandcamerastreamingthroughthewebapplication.

ThemainpageofthewebapplicationshowsthemovementcontrolsforthechassisandpiArm:

7. First,testthemovementcontrolsandensurethatboththemotorsrotateinthesamedirectionwhenyouselectForwardandintheoppositedirectionwhenyouselectReverse.

8. Next,ensurethatthearmcontrolsmovetheservoscorrectly.ForJoint2andHand,asingleservoshouldmoveandforJoint1,twoservosshouldmoveintheoppositedirection.

Thevideopage(accessedusingtheVideolinkinthetop-rightcornerofthewebapplication)showsthelivevideostreamfromthePicameramodule.Belowthestream,thereisalinktothecamerasettingspageprovidedbythestreamingserver.Notethatthereisnolinkbacktothewebapplicationfromthecamerasettingspage,soyoumustnavigatebacktoitmanuallyafterfollowingthislink.

ThereisalsoapagethatshowsboththevideostreamandcontrolsaccessedusingtheControl&Videolinkinthetop-rightcornerofthewebapplication.

ThearmandchassisconstructionNowthattheelectronicsareassembled,itistimetoassembletheroboticarmandchassis.Firstly,wewillgooverwhatpartsareneededtoconstructtherobot.

Inthecaddirectoryintheprojectfiles,thereareseveralDXFfilesforpartsthatareneeded;thefollowingisalistofallthepartsthatareneededtoconstructtherobot:

1xArm1_Main.dxf2xArm1_ServMount.dxf1xArm2_Main.dxf2xWheel.dxf1xSpacers.dxf1xCameraMount.dxf1xClaw_ServoAttachment.dxf1xBaseLayer.dxf

Onceallofthepartsaremachined,wecanstarttheassembly:

1. First,weneedtoattachthetwogearedmotorsandcastortothechassisbase.ThisisdoneusingfourM3screwsandnutsforeachmotorandfourM4screwsandnutsforthecastor.

2. Next,wecanattachtherelayboardandthePitothechassisbaseusingM3screwsandnutsaswellastwoofthespacersbetweenthechassisbaseandPCBs.

3. Next,wewillattachtheclawattachmenttooneoftheservos,whichwillbemountedattheendofthesecondarmassembly.First,useoneoftheplasticattachmentssuppliedwiththeservotomanuallymovetheservotohalfofitstravel(thisistoallowplentyoftraveloneithersideofthecurrentpositionforthecalibrationsteplateron).

4. Oncetheservoshaftisinthecorrectposition,wecanremovetheplasticattachmentandattachtheMDFclawattachment.Thisisdonebypushingtheservoshaftintotheholeinthecenterofthecircle.Thiswilltakesomeforce,butwillensurethattheMDFhasagoodgripoftheservoshaft.

5. Oncetheclawattachmenthasbeenattachedtotheshaft,useanM3washerandthescrewthatcamewiththeservostofastentheattachmentontotheservoshaftusingthetappedthreadattheendoftheservoshaft.

6. Next,wewillattachtheservotothearm2section;thisisdonebyfirstthreadingthecablethroughthesquarecutoutinoneofthearmsectionsandusingsomehotgluetofixtheservointothecutout,asshowninthefollowingimage:

7. Next,weneedtocutsix50mmlengthsofM4threadedbar,whichwilllaterbeusedtoassemblethetwoarmsections.

8. Next,wewillassembletheupperarmassembly.StartbyassemblingthetwosectionsoftheupperarmbyusingtwosectionsoftheM4barinthefirsttwoholesnearesttotheclawandspacethegapusingnineoftheMDFspacers.

9. InsertasectionoftheM4threadedbarthroughthetwoholesattheendoftheupperarmsection;thiswillbeusedtoconnecttotheservo,whichwillmovetheupperarmsection.

10. Next,wewillattachtheservothatwillmovetheupperarmsectiontothelowerarmsection;again,theservomustfirstbesetto50percentofitstravelbeforeyoudothis.

11. Now,attachasinglearmtotheservoandscrewitontotheservoshaft.12. Attachtheservoontothelowerarmpanelinthesamewayaswasdonewiththe

previousservo,asshowninthefollowingimage:

13. Next,wewilltaketheremainingtwoservosandattachthemtothetwomountingbracketsthatareattachedtothechassisbase.Theseservosshouldbothbesetto50percenttravelandalignedsuchthatoneservoisinthetop-rightcornerofthecutoutandtheotherisinthetop-leftcorner.Thisistoensurethattheshaftshavethebestchanceofliningupwhentheyareattachedtothechassisbase.

14. Next,thetwolowerarmpanelsmustbeattachedtothetwoservos.ThisisdonebypressingtheshaftintotheholesinthelowerendofthearmpanelsandfasteningtheshaftwithM3washersandthescrewssuppliedwiththeservos.

15. Now,thelowerarmassemblycanbeassembledinthesimilarwaytotheupper-armsectionbyfasteningthetwopanelstogetherusingtwooftheM4threadedbarsectionsandelevenoftheMDFspacers.

16. TheupperandlowerarmsectionscannowbejoinedusingasectionoftheM4threadedbar,asshowninthefollowingimage.Notethatthisshouldbeafairlyloosefasteningtoreducethefrictioninthisjointandthereforereducetheloadontheservo.

17. Now,wecanattachtheentirearmassemblytothechassisbasebyusinganM3screwoneachoftheservobrackets,asshowninthefollowingimage:

18. Now,wecanconnecttheservomountedinthelower-armsectiontothebaracrosstheupper-armsectionusingapieceofrigidcopperwire.Thisshouldbeattachedtogetthedesiredfieldofmovementontheupper-armsection,whichcanbemeasuredbymanuallymovingtheservoarm.

19. Thefinalstepoftheassemblyistoattachthecameratothemountingbracket;thecamerashouldfirstbedisconnectedtofeedtheflat,flexcablethroughtheslotatthebottomofthebracket,asshowninthefollowingimage:

20. Next,attachthecameratothebracketbyusingsmallsectionsofBlu-Tack(thisallowsustoadjusttheangleofthecameratotheoptimalangle)andplacethecameraattachmentintotheslotinthechassisbase.

Oncefullyassembled,therobotshouldlooksomethinglikewhatisshowninthefollowingimage:

CalibrationNowthatthearmandchassisarebuilt,weneedtocalibratethemotorsandservostoensurethattheyreactinthecorrectwaytothecommandsfromthewebapplication.Inthecaseoftheservos,donotattempttomovethemtoofarasthiswillcausedamagetothemorotherpartsoftheroboticarm.

ChassismotorsFirstly,wewillensurethatthechassismotorsbehavecorrectly.Thisissimplyacaseofrunningthemotorsineachoftheirdirectionstoensurethatthechassismovesinthedirectionintended.

Whenrunninginforwardorreversemotion,ifonemotorisrunninginthewrongdirection,thiscanbecorrectedbyswappingthepolarityofthemotor.Youcanswapthepolaritybyswappingtheconnectionsonthetwowiresleadingtoitfromtherelayboard.

Whenthemotorrunsintheclockwiseorcounterclockwiserotation,ifthebaserotatesinthewrongdirection,thenbothmotorsneedtohavetheirpolarityswapped.

Arm2andhandservosSincethesetwoservosoperateindependently,theyarefairlysimpletocalibrate,asallthatneedstobedoneistofindthelimitsoftherangeyouwanttheservostomovein.

Tofindthis,wewillusetheRPIOlibraryfromthePythonconsoletosetdifferentvaluesontheservo:

1. First,fromanSSHsessiononthePi,openanewPythonconsoleasroot(rootaccessisrequiredasthelibraryneedstoaccessmemorydirectlytocontroltheGPIOpins):

sudopython

2. Next,importtheRPIOlibraryusingthefollowinglineandcreateaServoobject:

importRPIO.PWMaspwm

s=pwm.Servo()

3. Now,youcansetthepositionoftheservousingthefollowinglineofcode,whereGPIOistheGPIOnumbertheservoisconnectedtoandVALUEisthetimingvalueforthePWMsignalsenttotheservo(thisshouldbebetween500and2500):

s.set_servo(GPIO,VALUE)

4. Repeatthelaststepuntilyoufindgoodvaluesforthemaximumandminimumvaluesoftheservothatgivereasonablelimitstothemotionoftheservo.

Oncetheoptimalvaluehasbeenfound,itshouldbeenteredintherobot_arm.confconfigurationfileintheappropriate_MAXand_MINconfigurationoptions.

Thearm1servosSincethesetwoservosoperateparallelywitheachother,thecalibrationprocedureisslightlymorecomplex.Wemustfirstdetermineapointonboththeservoswheretheyareinequalpositionsandarenotmovingtotryandcanceleachotherout.

1. Firstly,openaPythonconsoleasbefore:

sudopython

2. ImporttheGPIOlibrary:

importRPIO.PWMaspwm

3. Next,createtwoservoobjects,oneforeachservo:

s1=pwm.Servo()

s2=pwm.Servo()

4. Now,setastartingvalue(VALUE)forthefirstservo(onGPIOnumber,GPIO)thatiswithintherangeofmovementforthelowersectionofthearm(1500isagoodstartingvalue;however,youmayneedtoexperimenttofindthebestvalue):

s1.set_servo(GPIO,VALUE)

5. Now,weneedtofindavalue(VALUE)onthesecondservo(onGPIOnumber,GPIO)atwhichbothservosareatrestandnottryingtomove.Thisindicatesthatthetwoservosareinthesameposition.Notethatyoumayneedtomovethearmslightlytostoptheservosfromtryingtomove.Theweightofthearmmaykeeptheservosinmotioneventhoughtheyareinthesameposition:

s2.set_servo(GPIO,VALUE)

6. Oncethetwoservosareinthesameposition,makeanoteofthetwovalues(forexample,1400and1600)andcalculatethemidpointofthetwo(1500).Thisvalueshouldalsobeapositioninwhichboththeservoswillbeinthesameposition.

7. Nowthatweknowthisvalue,wecandefinethesetsfunction,whichwillsetboththeservostoagivenoffset,allowingustoderivetheupperandlowerlimitsforbothservos.Here,GPIO_1andGPIO_2aretheGPIOnumbersthateachservoisconnectedtoandVAListhemidpointvaluecalculatedinthepreviousstep:

defsets(position_delta):

s1.set_servo(GPIO_1,VAL+position_delta)

s2.set_servo(GPIO_2,VAL–position_delta)

8. Wecannowusetrialanderror,aswiththepreviousservos,tofindtheoptimalmaximumandminimumservospositionsbymakingcallstothesetsfunction:

sets(-300)

sets(0)

sets(1000)

…

9. Nowthatwehavethemaximumandminimumvaluesthatcanbepassedtothesets

function,wecaneasilyderivethevaluesthatneedtobesetintheconfigurationfileas(whereVAListhecalculatedmidpoint,SETS_MINandSETS_MAXarethemaximumandminimumvaluespassedtothesetsfunction,SETS_MINisnegative,andSETS_MAXispositive):

ARM_1_A_SERVO_MIN=VAL+SETS_MINARM_1_A_SERVO_MAX=VAL+SETS_MAXARM_1_B_SERVO_MIN=VAL-SETS_MAXARM_1_B_SERVO_MAX=VAL–SETS_MIN

Oncethesevaluesarederived,theycanbeenteredintotherobot_arm.confconfigurationfile.

TroubleshootingThefollowingareafewissuesyoumaycomeacrosswhilebuildingandusingtheroboticarm,wherethecausesoftheissuesandinformationonhowtheproblemcanbefixed.

ThevideostreamhasasubstantialdelayThisdelaycanbecausedifyouattempttostreamattoohighofaresolution.Thefirstthingtodoistotryandreducetheresolutionyouarestreamingat(notethatthishastobedoneeverytimethePiisrebooted).

Iftheissueisstillthere,thenyoumaywanttotryreducingtheJPEGqualityandframerateoptionsonthestreamingserverconfigurationpage(whichisaccessibleviathelinkonthevideostreampageofthewebapplication).

TheservosmakealoudhummingnoiseTheservoscanoftenmakealoudhummingsoundwhentheyareundersubstantialload.Usually,thisisthecasewhenthearmisfullyextendedorisattemptingtoliftaload.Ifthiscontinues,anextendedlengthoftimewillconsumemorebatterypowerandcouldlowertheexpectedlifetimeoftheservos;however,inthisproject,thisbehaviorisnormaloperation.

ControloftherobotislostIfthecontroloftherobotislost,themostlikelycauseisthelossoftheWi-Fisignal.However,othercausescanincludelowpowerintheUSBbatterybankoradditionalloadontheservosthatcausesthemtodrawmorepowerthanusual(however,thisshouldonlyevercauseanissuewhenthebatterybankisrunninglow).

ThearmjumpstonewpositionsThiscanbecausedbytoomanyrequeststomoveanaxisofthearminagivendirectionbeingsentinaperiodoftime.Ifyoufindthatittakestoolongtomovethearm,thenconsiderincreasingthevalueofSERVO_DELTAinthewebapplicationconfigurationfile.

SummaryInthischapter,wehadalookatyetmorewaystointerfacewithhardwareovertheGPIOportthatincludesusingpulsewidthmodulation,whichcanbeusedtodrivedevicessuchastheservosusedinthischapter.Wealsotookalookathowtoemulateananalogsignal,whichcanthenbeused,forexample,tocontrolthebrightnessofanLED.

WealsotookalookatthewaysinwhichtheRaspberryPicameracanbeaccessedremotelyusingtheV4Lstreamingserver.Intheserver,thesamecontrolandstreamingoptionsthatareavailabletothelocalapplicationsaremadeavailabletothedevicesonthesamenetwork.

Inthenextchapter,wewilllookathowtousethePiforatrueubiquitouscomputingproject,whichwillcombineaninformationdisplayintoafairlystandardmirror.

Chapter9.MagicMirrorInthischapter,wewillcreateamirrorthatiscapableofbeingbothareflectivesurfaceandaninformationdisplaythatcanbeusedtoshowcustomizedinformation.

Thiswillbedonebytakingadvantageofthepropertiesofatwo-waymirror(commonlyusedforshopsecurity),whichwillallowlighttopassthroughitasifitwasaglasswhentheothersideisdarkerandbehavelikearegularmirrorotherwise.

ThisprojectisbasedontheMagicMirrorprojectbyMichaelTeeuw.Moreinformationabouthisoriginalversioncanbefoundathttp://michaelteeuw.nl/tagged/magicmirror.

WhatyouwillneedThefollowingisalistofthingsthatyou’dneedforthisproject:

TheRaspberryPiAUSBkeyboard(forsetuponly)AVGAmonitorA6mmplywoodA12mmplywoodAsheetoftwo-waymirroredacrylic(www.cutplasticsheeting.co.uk/mirrored-sheeting/two-way-acrylic-mirror)M4machinescrewsandwashers

ToolsyouwillneedThefollowingisalistoftoolsyouwillneedtoconstructtheplywoodenclosureforthemirror:

A25mmForstnerdrillbitAlargeelectricdrillordrillpressAjigsawArouterandtableAstraight,topbearing,andguidedrouterbit(www.screwfix.com/p/titan-flush-trim-bit-with-bearing-shank-12-7-x-25mm/72588)A4mmrebaterouterbit(www.screwfix.com/p/biscuit-router-cutter-no-20-shank-41mm/86179)

Notethathere,arouterandtablearerequiredtomachinetheplywoodenclosureforthemirror,whicharebothtoolsthatyoumaynothaveeasyaccessto.Ifthisisthecase,aswithlasercuttinginthepreviouschapters,agoodplacetostartwouldbetolookforalocalhackerspace,whichwouldlikelyhavethesetoolsandmemberswhowouldbehappytohelpyouusethem.

TherouterbitsIhavelinedherearefora1/2inchshank,whichmustfittherouteryouintendtouse.Ifyourroutercanonlyfind1/4inchshank,thenyouwillneedtofindalternativecutters.

Ifyoustillhavetroublegettingaccesstoone,thereisanalternativewaytobuildthisprojectthatwillforgotheplywoodenclosureattheexpenseofsomeaestheticappealofthemirror.

Themonitoryouselectshouldpreferablybewidescreenifyouintendtousethemonitorinportraitmode(aswillbedoneinthischapter).Althoughitisnotrequired,thebuildprocessismadeeasierifthecontrolbuttonsforthemonitoraremountedonthebackofthedisplay.

TheoryThetwo-waymirrorthatwillbeusedinthisprojecthasanimportantproperty.Whenonesideofthemirrorisexposedtoabrighterambientlightthantheother,thislightisreflectedinthemirrorsurfaceandisallowedtopassthroughtotheother(darker)sideofthemirror.

Typically,thispropertyisusedtocontrolhowthemirrorisusedinsecurityapplications,forexample,ashopmayfitsuchamirrorbetweenanofficeandtheshopfloorsothatthoseintheofficecanstillseewhatishappeningontheshopfloor.Forthistohappen,theofficemusthaveveryminimallightingtoensurethatthebrightlightfromthealreadywell-litshopfloorpassesthroughtotheofficeandthatnolightfromtheofficeleaksthroughthemirror,exposingittotheshopfloor.

Inourproject,wewillusethispropertytocreateadisplaythatshowswhitetextandgraphicsonamirroredbackgroundbyplacingasectionofthemirrorinfrontofanLCDmonitor.

Thisispossibleifyoukeepthedisplaydarkintheareaswherethemirrorsurfaceshouldbepreservedandusebrightwhitetextandgraphicswheretheyshouldbeshowninsteadofthemirrorsurface.Bydoingthis,youcanallowthemtopassthroughthemirrorsurfaceprovidedthatthebrightnessofthedisplayisgreaterthanthatoftheambientlightintheroomtheprojectisin.

Forthisreason,itisworthnotingthatthisprojectwillnotworkifthemirrorsurfaceissubjecttobrightsourcesoflight,soitisbesttokeepthemirrorpointedawayfromlargewindowsorlights.

Whilesearchingforasuitablemonitor,itisalsobettertogetthehighestcombinationofbrightnessandcontrastratiopossible,asthiswillallowyoutogetbrightertextandgraphicsfromthedisplay.Thisinturnwillimprovethequalityoftheimageonthemirrorsurfacewhilemaintainingadarkbackgroundsoasnottocauseanylightleakagewherethedisplayshouldremainamirror.

ThewebapplicationThewebapplicationwewilluseforthemirrorisessentiallyaframeworkbuiltusingFlask,whichprovidesacommoninterfaceforindividualwidgetsdisplayedonthemirror.Inordertogetthedesiredeffectwherethewidgetsarevisiblethroughthemirror,thepagemusthaveablackbackgroundwithwhitetextandgraphics.Forbestresults,thetextshouldbeaslargeaspossiblesothatitallowsmaximumlighttopassthroughthemirror’ssurface.

DevelopinganewwidgetEachtypeofwidgetthatcanbeshownonthemirroriscomprisedoffourfiles:

Aserver-side(Python)scriptfile(widgets/CLASSNAME.py)AJinja-styletemplatefile(templates/widgets/CLASSNAME.html)ACSSfile(static/widgets/CLASSNAME/style.css)Aclient-side(JS/jQuery)scriptfile(static/widgets/CLASSNAME/script.js)

Here,CLASSNAMEistheclassnamegiventothewidgetthatisusedinthewidgetconfigurationfilestocreateaninstanceofthewidgetonthemirrordisplay.Templatesforthesefilescanbegeneratedusingthefollowingscript(assumingthatyouarecurrentlyinthemirror_webapp/directory):

./make_new_widgetCLASSNAME

Wewillnowtakealookatthedemowidgettoseewhatneedstobedoneifyouwanttoimplementyourownwidgets.

ThePythoncodeThefirststeptodevelopanewwidgetistocreateaPythonscriptthatwillprovidethewebapplicationwiththedataitneedstooperate.Thiswillhaveaccesstotheconfigurationoptionsthataresetunderthe[widget]sectionoftheconfigurationfile.ThemainpartofthePythonscriptistheget_datafunctionwhichmustreturnadictionarythatwillbemadeaccessiblefromthewidgetdatawebserviceandtranslatedintoJavaScriptObjectNotation(JSON):

fromAbstractWidgetimportAbstractWidget

classDemoWidget(AbstractWidget):

defget_data(self,config):

self.logger.info('Gettingdatafordemowidget')

data={'greeting':'NoTextSet!'}

if'text'inconfig:

data['greeting']=config['text']

returndata

Here,youcanseetheget_datafunction,whichtakesthewidgetconfigurationasadictionaryparameterandreturnsadictionary.Thisisonlyasimpleexamplethatreturnsatextstringtakenfromtheconfigurationfile.However,thereisalotofscopefortheadditionalprocessingthatcanbedonehere(refertothecodeforsomeoftheotherwidgets,forexample).

Youwillalsonoticethatthefirstlineofthefunctionisusedtologinformation.Thiscanbeveryusefulfordebuggingtheapplication.Thelogiskeptinthe/home/pi/mirror_webapp/mirror_app.logfileandcontainsthelogoutputfromtheframeworkapplicationandeachconfiguredwidget.

Textcanbeoutputtothelogatseverallevels,fromleastseveretomostsevere:debug,info,warning,error,andcritical.

Thedatareturnedbytheget_datafunctionismadeavailableonthewidgetdataweb

serviceavailableat[PI_IP]/widget_data/[widget_id].Here,PI_IPistheIPaddressofthePiandwidget_idisthewidgetIDthatisgivenbythefilenameoftheconfigurationfile(thatis,awidgetwiththeconfigurationfilenameclock.confwillhavethewidgetIDclock).

TheJinjapagetemplateThewebpagefortheapplicationisgeneratedbyFlaskusingJinja2templates.ThisallowsaverysimpleandcleanwayofbuildinganHTMLstructuredynamically.

Thefirstthingrequiredinthefileistheextendsstatement,whichtakesacommonsectionofcodeusedforeachwidgetandaddsthecontentsblocktoitbasedontherestofthefile:

{%extends"widget.html"%}

Thenextsectionisthewidget_contentsblock.Thisiswheretheactualcontentsofthewidgetshouldbewritten.

Here,youhaveaccesstoadatavariablethatcontainsthedatareturnedbytheget_datafunctioninthePythoncodeforthewidget:

{%blockwidget_contents%}

<p>{{data.greeting}}</p>

{%endblock%}

Typically,youwillfindthatalotofdynamiccontentishandledbyJavaScript,asoncethePihasbooted,thewebpagewillneverberefreshedundernormaloperation.Hence,thisHTMLgenerationstepisonlyeverperformedonce.

TipFormoreinformationontheJinjatemplatelanguage,refertothedocumentationathttp://jinja.pocoo.org/docs/dev/.

TheJavaScriptcode

Sincethedemowidgetdoesnothaveanydynamiccontent,thefunctionsintheJavaScriptfilearejustemptyplaceholders.However,themainpointtobeshownhereishowthefunctionsarecalledbytheframework.

Firstly,thereisaclosure(awayoflimitingscopeinJavaScripttogetsomethingthatbehavessimilartoaclassinobject-orientedlanguages)thatdefinesthewidget.Thiscanbeusedtostoreinstance-specificvariablesforthewidget:

varDemoWidget=function(){

}

Next,thereisapublicfunctionthatisexecutedwhenthepagefirstloads.Thisisusedtogetthewidgetintoitsinitialstate(forexample,populatingalistofRSSitemsbeforethenextupdateorsettingthetimeofaDateobject):

DemoWidget.prototype.init=function(widgetDOM){

return;

};

Thenextfunctioniscalledatintervalsoftheupdate_timevariablesetinthewidgetconfigurationfile(refertotheConfigurationsectionlaterinthischapter).Thisshouldbeusedtoupdatethecontentsofthewidgetsothatthemirrorkeepsdisplayingnewinformation,forexample,refreshingalistofnewsstoriesorincrementingthesecondhandofaclock:

DemoWidget.prototype.update=function(widgetDOM){

return;

};

ThewidgetDOMparametergiventoboththefunctionsistheDocumentObjectModel(DOM)ofthewidgetcontainerelement.ThisprovidesasafeandeasywaytoaccesstheelementsofyourwidgetwithouthavingtorelyonIDattributesintheHTML.

Forinstance,toaccessacertainparagraphelementofthewidget,youwouldfirstassignaclasstotheelementintheHTMLtemplate,shownasfollows:

<pclass="news-story-title"></p>

Then,youcaneasilyaccesstheelementandchangeitstestusingthefollowinglineofJavaScript:

widgetDOM.getELementsByClassName("news-story-title")[0].innerText="Hello,

World!"

TipFormoreinformationonJavaScriptdevelopment,refertothew3schoolsreferencepagesatwww.w3schools.com/jsref.

ThePisetupTheinitialstepstosetupthePiaretogetacopyofRaspbianinstalledonanSDcardofatleast4GB(although8GBorlargerispreferable),asdescribedinChapter1,RaspberryPiPirateRadio,andifdesired,connectthePitoyourWi-Finetwork.ThisprojectwillkeepthePioutsidethedisplayenclosuresothatWi-Fiisonlyreallyneededifawiredconnectionisnotavailable.

RotatingthedisplayYoumaywishtorotatethedisplaytousethemirrorinaportraitorientation,inwhichcasethevideooutputofthePiwillalsoneedtoberotated.Fortunately,thisisdonebyasimplechangetoaconfigurationfile:

1. Openthebootconfigurationfileusing:

sudonano/boot/config.txt

2. AddthefollowinglineandreplaceNwithoneoftheoptionsdescribedinthenextscreenshot:

display_rotate=N

Theconfigurationfilelookssimilartothefollowingscreenshot:

3. SavethefileandrebootthePitoseethechanges:

sudoreboot

ThepossibleoptionsthatcanbegivenforNare:

0:Normaldisplay1:Rotate90degreesclockwise2:Rotate180degreesclockwise3:Rotate270degreesclockwise

DeployingthewebapplicationNowthatthePiissetup,wecangoaheadwiththedeploymentofthewebapplicationonthePi.Onceagain,thisisaFlaskapplication,sotheprocedurewillbeverysimilartothatusedinthepreviousprojects:

1. First,startbycopyingtheconfig_filesandmirror_webappdirectoriestothe/home/pidirectoryontheRaspberryPi.

2. Now,wewillensurethatthesoftwareonthePiisuptodateandinstalltherequiredsoftwaretorunthewebapplication(notethatthelastlinesherearePythonlibrariesrequiredbysomeofthewidgets):

sudoapt-getupdate

sudoapt-getupgrade

sudoapt-getinstallpython-pipgitgunicornsupervisornginx

sudopipinstallrequestspytzfeedparser

3. Next,wewilldownloadtheFlaskcoderepositoryandinstallit:

gitclonehttps://github.com/mitsuhiko/flask.git

cdflask

sudopythonsetup.pyinstall

cd

4. Now,wewillcopytheNginxconfigurationforthemirrorwebapplication,enableit,andrestartNginxsothatitstartshandlingrequestsforthemirrorwebapplication:

sudocpconfig_files/nginx/mirror.conf/etc/nginx/sites-

available/mirror.conf

sudoln-s/etc/nginx/sites-available/mirror.conf/etc/nginx/sites-

enabled/

sudorm/etc/nginx/sites-enabled/default

sudonginx-t

sudoservicenginxrestart

5. Next,wewillcopythesupervisorconfigurationfortheapplication,whichwillallowthewebapplicationtobeservedbythePi,assoonasitboots:

sudocpconfig_files/supervisor/mirror_webapp.conf

/etc/supervisor/conf.d/mirror_webapp.conf

6. Next,copythedefaultwidgetconfigurationfiles.Fornow,wewilljustusethedefaultsuntilthemirrorisfullysetupandgooverthestepstoconfigurewidgetsandstyleslaterinthechapter:

cpconfig_files/mirror_app.conf~

cp-rconfig_files/widgets/widget_configs/

7. Finally,updatesupervisortoenablethewebapplication:

sudosupervisorctlreread

sudosupervisorctlupdate

sudosupervisorctlstartmirror_webappp

Oncethishasbeendone,youshouldbeabletobrowsethewebapplicationusingtheIPaddressofthePifromanyPConthesamenetwork.Ondoingso,youshouldbegreetedwithapagesimilartothatshowninthefollowingscreenshot:

Don’tworryifthepagelooksbadlyrendered,asthedefaultwidgetconfigurationisdesignedtobeshownonaportraitmonitorandthefontsizesaresetrelativetothewidthofthescreen.WhendisplayedonthePi,thislooksalotbetter.

SettingupChromiumNowthatwehavethewebapplicationsetup,wecanmoveontoinstalltheChromiumbrowser.WewillusethebrowserinthekioskmodetodisplaythewebapplicationonthePIautomatically,whenitboots.TosetupChromium,performthefollowingsteps:

1. Firstly,wemustconfigurethePitobootstraightintoLXDE(thedefaultwindowmanagerusedonRaspbian)insteadofaconsole.ThiscanbedoneusingthePiconfigurationutility:

sudoraspi-config

2. Next,selecttheEnableBoottoDesktop/ScratchoptionandhitEnter.

3. Now,selecttheDesktopLoginasuser‘pi’atthegraphicaldesktopoptionandhitEnter.

4. Next,selecttheFinishoptionandwhenaskedwhetheryouwouldliketorebootnow,selectNo.

5. Oncethatiscomplete,wenowneedtoinstalltheChromiumbrowser:

sudoapt-getinstallchromiumx11-xserver-utilsunclutter

6. Next,wewillmodifytheLXDEautostartscriptsothatChromiumautomaticallystartsandbrowsestothewebapplicationpagewhenthePiboots:

sudonano/etc/xdg/lxsession/LXDE/autostart

7. Commentoutthefollowingline.Thiswilldisablethedefaultscreensavertoensurethatthewebapplicationalwaysremainsvisible:

@xscreensaver-no-splash

8. Addthefollowinglinesattheendofthefile.Thefirstthreedisablethepowersavingfeaturesthatwouldautomaticallyturnthemonitorblankandturnitoffafteraperiodofinactivity.ThefinallinewillstarttheChromiumbrowserinafullscreenkioskmodeandbrowsetothewebapplication:

@xsetsoff

@xset-dpms

@xsetsnoblank

@chromium--kiosk--incognitohttp://localhost

Bythispoint,theautostartfileshouldlooksimilartothefollowingscreenshot:

9. Finally,rebootthePitotestthesetup:

sudoreboot

Allbeingwell,youshouldseethePibootintoLXDE(indicatedbytheRaspberryPilogoshownonawhitebackground)andshortlyafterthat,Chromiumshouldstartandbrowsetothewebapplication.

EnclosureconstructionNowthattheelectronicsandsoftwareinstallationiscomplete,wecanmoveontobuildtheplywoodenclosureforthemirror.Ifyoudonothaveaccesstoarouterandtableforthisproject,thenrefertotheBuildingthemirrorwithoutanenclosuresectiondescribedlaterinthechapterforinstructionsonhowtoconstructthedisplaywithouttheplywoodenclosure.

NoteWhenusingpowertools,propersafetyprecautionsshouldbetaken.Eyeandearprotectionshouldalwaysbewornandmains-poweredtoolsshouldbeprotectedbyusingaresidualcurrentdevice(RCD).

First,weneedtomeasurethemonitortodetermineboththesizeofthemirroredacrylicsheetthatneedstobeorderedandthesizestowhichthepanelsfortheenclosureshouldbecut.

Theupcomingdiagramshowsthepanelsthatmustbecutouttomaketheplywoodenclosure.Eachofthedimensionsaregivenbythefollowingcalculations:

W=monitorwidth+24H=monitorheightWb=W+10Hb=H+10T=monitorthickness+9

NoteNotethatallthesizesareinmm.

Toconstructtheenclosure,performthefollowingsteps:

1. Whiletakingthemeasurementsoftheheightandwidth,itisadvisabletoleavearound2mmoneachsideofthemonitor,whichwillallowustorectifyanyerrorsinthemeasurementwhilemanufacturing.

2. Inordertotakethenextmeasurement,wemustfirstremovethefrontplasticbezelfromthemonitor.Thisisusuallyheldonwithaseriesofsmallplasticclipsaroundtheedgeofthemonitor,asshowninthefollowingimage.Toremovethem,useasmall,flatscrewdrivertoprizeopenthegapbetweenthebackofthemonitorcaseandthefrontbezel.Gradually,workaroundthemonitoruntilalltheclipsarereleased.Thefrontbezelshouldnowliftoffwithease.

3. IfthemonitorhasanybuttonsorLEDsonthefrontpanel,thereislikelyanadditionalPCBthatmustberemovedfromthefrontbezel.Thisusuallyrequiresustounscrewtheboard.

4. Oncethebezelisremoved,wecannowmeasurethespacerequiredinsidetheboxforthemonitor.Thisisthedistancefromthebackofthemonitor(specificallytheVESAmountingpoints)tothefront(preferablylevelwiththedisplaysurface),asshowninthefollowingimage.Itisadvisabletoaddatleastanadditional5mmtothismeasurement,asitiseasytoaddwasherstomovethemonitorforwardifthepanelsarecuttoolarge.However,thisisimpossibletorecoverifyoucutthepaneltoosmall.

5. Onceyouhavethesethreemeasurements,youcansubstitutethemintothecalculationsshowninthediagram.Usingajigsaw,cutthepanelstosize.Youwillneedtwoofboththelongandshort12mmplywoodsidepanelsandoneoftheback6mmplywoodpanel.

6. Oncethesepanelsarecut,itistimetocuttheslotsinthemtoplacethemirroredacrylic.Thisisdoneusinga4mmrebaterouterbitinaroutertable,whichcanbeseenintheupcomingimage.Todothis,performthefollowingsteps:

1. Firstly,ensurethattherouterisfirmlyfixedintothetableandthebitistightenedcorrectlyintotherouter.

2. Next,usetherouter’sdepthlocktofixtheheightoftherouter,sothattheloweredgeofthebladesarearound4-5mmabovethetable.

3. Now,movethefencesothataround5-6mmofthecutterisexposedonthefrontofthefence(thatis,thecuttercanonlycutupto5-6mmfromthematerialpassedalongthefence).

7. Oncetherouterandtablearesetup,itisagoodideatomakeafewtestcutsonascrappieceofmaterialtoensurethattherouterissetupcorrectly.Aimtogetaslotthatisaround5-6mmdeepintotheplywoodandaround4mmawayfromoneedge,asshowninthefollowingimage:

8. Onceyouarehappythatthesetupiscorrect,youcanmachinetheactualpanelstoendupwithasetofpanels,asshowninthefollowingphotograph.Atthisstage,itisagoodideatosandthepanelswithsomecoarsegritsandpapertoremoveanyraggededgesleftbytherouterorjigsaw.

9. Thenextstepistoassemblethefoursidepanelsthatformtheoutsideoftheenclosure.Thisisdoneusingtwoscrewsateachendofthelongpanelsthatarescrewedintotheendsofthetwoshortpanels.Forthis,wewillusescrewsthatareatleast1inchinlength,butnomorethan2inch.Performthefollowingsteps:

1. First,wemustdrillclearanceholesintotheendsofthetwolongsidestoallowthescrewshafttopassthrougheasily.Thisholeshouldbejustlargerthantheshaftofthescrew,butsmallerthanthehead.

2. Next,alignoneofthelongpanelsagainstashortone,asshowninthefollowingfigure,andusetheclearanceholeasguidancetodrillapilotholeintheendoftheshortsidepanel.Thisholeshouldbearound0.5-1mmsmallerthantheshaftofthescrew.

3. Repeatthepreviousstepuntilallthejointshavebeenfastened,ensuringthattheslotforthemirrorrunsallthewayaroundtheinsideedge,asshowninthefollowingphotograph:

10. Thenextstepistoattachtherear6mmplywoodpaneltothebackoftheenclosureframe.Thiscanbedoneusingseveralself-tappingscrewsaroundtheedgeoftheenclosure.Notethatthispanelhasintentionallybeenmadelargerthanwhatisrequired.

1. Firstly,withtheenclosureplacedontopoftherearpanel,drawaroundtheinsideoftheenclosuretohelpmarkoutthepositionsfortheclearanceholessothatthescrewsholdontothebackpanel.

2. Next,usingthismarkingasaguide,drillseveralclearanceholesaroundtheperimeteroftheenclosure.Typically,twoholesontheshortpanelsandthreeholesonthelongonesshouldbeenough.

3. Oncethisisdone,drillpilotholesforthescrewssothattheygointothesidepanelsandattachthebackpaneltotherestoftheenclosure.

11. Thenextstepistotrimtheexcessmaterialfromthebackpanel(thewholeideaherewastoremovetheneedforaccuracywhilecuttingandfittingthebackpanel).Thisisdoneusingastraight,bearingguided,routercutter.

1. Firstly,movethefencetowardthebackoftheroutertable(wewillnotuseitasaguidehere)andfitthestraightbitintherouter.

2. Next,usingthedepthstop,movetheroutertoapositionwherethebearingisonthesamelevelasthe12mmsidepanels,sothatthereisenoughclearancetoallowthecuttertoremovetheexcessmaterialonthebackpanelonly.

3. Now,youcanmachineawaytheexcessmaterialonthebackpanelbykeepingtheenclosuretightagainsttherouterbitwhilemakingapassalongalltheedgesoftheenclosure.Oncethisisdone,thepanelshouldlooksimilartothefollowingimage:

12. ThenextstepistomarkthepositionoftheVESAmountsonthebackpanelinordertodrilltherequiredholesinthebackpanel.Theeasiestwaytodothisistocarefullyremovethedisplayassemblyfromtherearplastichousing,usingthefollowingstepsasaguide:

1. Thedisplayassemblyisrarelyfixedintotheplastichousingbyanythingotherthanthefactthatitisenclosedby.So,ifwegiveenoughforce,thedisplaypanelandelectronicsenclosurebehindthedisplaypanelwillberemoved.

NoteBecarefulwhenremovingthedisplayassemblyasthedisplaypanelandelectronicsenclosureareusuallynotfixedtoeachotherandexcessstresscoulddamagethecablesrunningbetweenthetwo.

Itisalsonotadvisedthatyouapplypowertoamonitorwiththebackcoverremovedastherearepotentiallydangerousvoltagesintherearelectronicscabinet.

2. Oncethisisdone,youshouldbeabletoplacetherearplasticcaseintotheenclosureandeasilymarkthepositionsofthefourVESAmountingholes.

3. Atthisstage,itwouldalsobeusefultomarkthepositionoftheholethatwillallowpowerandvideocablestoreachthemonitor.Thisholeshouldbeatleast25mmindiametersothatitaccommodatesanIECpowerconnector.

4. Oncetheholesaremarked,youcannowputthedisplayassemblybackintotherearplasticcase.

13. Oncetheholesinthebackpanelaremarked,thepanelcanberemovedandtheholesdrilledwiththefollowingsteps:

1. ThefourholesfortheVESAmountcanbedrilledusinga4.5mmdrillbit.2. The25mmholewillhavetobedrilledwitheitherafairlypowerfulmainshand

drillor,better,adrillpressusingaForstnerdrillbit.

14. Oncethebackpanelhastherequiredholesdrilledinit,itisworthgivingitaquicksandoverbyusingacoarsegritsandpaper,justtotidytheedgeleftbytherouterandForstnerdrillbit.

15. Next,reattachthebackpanelontotherestoftheenclosureusingthescrewholesmadepreviously.

16. Atthispoint,itisworthpoweringupthemonitorandensuringthatthedisplayissettofairlyhighcontrastandbrightnesssettingsinordertogetthebestimagequalitythroughthemirroredacrylic.

17. Oncethisisdone,feedthecablesthroughtheholepreviouslymadeforthem.LineuptheVESAmountwiththeholesdrilledforthemandscrewthemonitorintoposition.

Ifyourmonitorhasbuttonsmountedonthefrontpanel,youcansimplyplacethePCBtheyaremountedonbehindthemonitorwithintherangeofthecablethroughwhichtheyareconnectedtothemonitor.

Notethatifthemonitoristoofarbackintheenclosure(thatis,thedisplaysurfaceismorethan1mmawayfromtheslotforthemirror),thenyoumayneedtoaddsomewashersandspacerstothescrewstomovethemonitorslightlyforward,asshowninthefollowingimage:

Bythispointtheenclosureshouldlooksomethinglikethefollowingimage:

18. Thefinalstepistoinsertthemirroredacrylicpanelintotheslotcutforit.Thiscanbeeasilydonebyremovingoneoftheshortsidepanelswiththefollowingsteps:

1. Firstly,removethescrewsthatholdtheshortpanelinplaceonboththelongsidepanelsandthebackpanelandremovethepanel.

2. Youshouldnowbeabletoslidethemirroredacrylicpanelintotheenclosureeasily.

3. Atthispoint,youmaywishtopoweronthemonitoroncemoretocheckwhetherthedisplaysettingsleakanylightthroughthemirrorpanelwhenthedisplayisblack.Ifso,turnthebrightnessdownslightly.

4. Thefinalstepistoreattachtheshortsidepanelandtheenclosureiscomplete.

Sincethebuttonsonthemonitorarenolongereasilyaccessiblefromoutsidetheenclosure,itisimportanttoensurethatthemonitorwillautomaticallyturnonwhenpowerisappliedtoit.Thiswillbethemethodusedtoenableanddisabletheinformationdisplayonthemirror.

NoteAstheenclosureisalmostfullyenclosed,itisdiscouragedthatyouleavethemonitoronforalongperiodoftimetoavoidexcessivebuildupofheatinsidetheenclosure.Instead,itisrecommendedthatyouonlyapplypowertothemonitorwhentheinformationdisplayisdesired.

Ifdesired,hardwarefittingscanbeusedtomakethemirrorwallmountable.However,fornow,wewilluseoursasadeskmountedmirroronly.Itisrecommendedthatyouplacethemirroragainstawalltoensuregoodstability,asitshighcenterofgravitydoesmakeitmoreliabletofalloverevenifverylittleforceisappliedtoit.Ifthisisanissue,thenyoucoulduseitinthelandscapemodebychangingthedisplayrotation.

BuildingthemirrorwithoutanenclosureIfyoudonothaveaccesstothetoolsrequiredtobuildtheplywoodenclosure(orwouldsimplypreferamoremodern-stylemirror)thenyoucanadaptanexistingmonitorintoamirrorrelativelysimplywithoutanytools.Allthatisrequirednowisanadhesive.

Youmaywishtouseatemporaryadhesive,suchasacleartapeorhotglueforthistoensurethatthemonitorcanbereusedifyoudecidetoremovethemirrormaterial.Althoughnothingisstoppingyouusingsomethinglikeacontactadhesive,suchasAraldite,foramorepermanentfitting.

1. Thefirststeptoconstructthedisplayistomeasurethesizeofthemirrormaterialthatwillbeneeded.Theseareessentiallythedimensionsofthescreenthatisexposedontheinsideoftheplasticbezelaroundthesideofthemonitor(refertothefollowingimage).Orderthemirrormaterialtobecutafewmillimeterssmallertoensurethatitwilldefinitelyfitwithintheinsideofthebezel.

2. Onceyouhavethemirrormaterial,youshouldfindthatitsimplydropsintothebezelwitharound1mmsparedoneachside.

3. Next,usingyouradhesiveofchoice,fixthemirrormaterialintothebezelofthemonitor.Itisimportantheretoavoidgettingadhesiveofanytypeonthedisplaysurface,asthiscandamagethemonitor.

ThePienclosureSincethePiisnotpartoftheenclosurewehavebuilt,youmaywishtokeepthePiinanexternalenclosure.Therearemanyoftheseavailableatonlineretailers.OneofmypersonalfavoritesisthePibowrangebyPimoroni(http://shop.pimoroni.com/products/pibow-raspberry-pi-case).

ConfigurationNowthatthewebapplicationhasbeendeployedtothePiandthedisplayenclosureisconstructed,itistimetoconfigurewhatinformationisshownandhowitisshownonthemirror.

Notethatwhenchangingthestylesheet,simplyreloadthepageinChromiumbypressingF5onaconnectedkeyboardtoshowthechange.Changestowidgetconfigurationswillrequireyoutorestartthewebapplicationbyusingthefollowingcommands:

sudosupervisordstopmirror_webapp

sudosupervisordstartmirror_webapp

WidgetsThewidgetsareconfiguredusingseveralconfigurationfilesinthe/home/pi/widget_configs/directory.Eachwidgetthatisdisplayedonthemirrorrequiresitsownconfigurationfile.

Theconfigurationfilesaredividedintoseveralsections:core,ui,position,andwidget,eachcontainingseveralvaluesrelatedtothewidget.Theseoptionsaredescribedasfollows:

core

class:Thenameofthewidgetclassupdate_time:TheintervalatwhichtheUIisrefreshed(inseconds;itdefaultsto1minuteiftheintervalnotprovided)title:Thetitleofthewidget(canbeleftblanktohidethetitle)

ui

width:Thisisthewidthallocatedtothewidget(inpixels)show_borders:Ifaborderistobedrawnaroundthewidget

position

type:Thisisthetypeofpositioning(top,bottom,left,right,andfloating)index:Thisisthenumberthatdenotesthepositionofthewidgetinabar(onlyvalidifthetypeisoneoftop,bottom,left,andright)x:Thisisthedistancebetweentheleft-handsideofthewidgetandtheleftofthemirror(onlyvalidiftypeissettofloating)y:Thisisthedistancebetweenthetopofthewidgetandthetopofthemirror(onlyvalidiftypeissettofloating)

widget:Thiscontainsconfigurationinformationspecifictothewidget

Theeffectsofthepositionconfigurationoptionsareshowninthefollowingdiagram:

IncludedwidgetsHereisalistofthewidgetsthatcomewiththemirrorwebapplicationandalistoftheirconfigurationoptions:

Digitalclock(class:DigitalClock)

timezone:Thetimezoneforwhichthetimeisdisplayed(forexample,US/Eastern)

Analogclock(class:AnalogClock)

timezone:Thetimezoneforwhichthetimeisdisplayed(forexample,US/Eastern)

Textcalendar(class:TextCalendar)

timezone:Thetimezoneforwhichthedateisdisplayed(forexample,US/Eastern)

Currentweather(class:Weather)

location:Thelocationforwhichthecurrentweatherconditionsaredisplayed(forexample,Oxford,UK)

RSSfeed(class:RSSFeed)

feed_url:TheURLfortheRSSfeednum_items:Thisisthenumberoffeeditemstobedisplayed(itdefaultsto10ifitisnotset)

RSSheadlineticker(class:RSSTicker)

feed_url:TheURLforRSSfeednum_items:Numberoffeeditemstofetch(thisdefaultsto10ifitisnotset)text_type:Thisisthetypeoftexttobedisplayed(eithertitleforashortheadlineorsummaryforamoredetaileddescription)ticker_update_time:ThisisthetimeintervalshownbetweennewRSSitems(inseconds)

ExampleconfigurationsHereareacoupleofexampleconfigurationfileswithanexplanationofwhateachvaluedoes;botharetakenfromthedefaultwidgetconfigurationincludedinthecodeforthischapter.

bbc_ticker.conf

TheBBCnewsticketisshownatthebottomofthemirrorusingthedemoconfiguration.ThiswidgetgivesanewheadlinefromtheBBCUKnewsRSSfeedevery10seconds:

[core]

class=RSSTicker#UsingtheRSSTickerwidget

title=BBCUKNews#Giveitatitle

[ui]

show_borders=true#Showtheroundedbordersroundthewidget

width=450#Allowthewidgettobeupto450pixelswide

[position]

mode=bottom#Putthewidgetinthebottombar

index=1#Thisisthesecondwidgetfromthecorner

[widget]

#ThisistheBBCUKnewsRSSfeedURL

feed_url=http://feeds.bbci.co.uk/news/uk/rss.xml

text_type=summary#Justdisplaytheshorttitle

ticker_update_time=10#Giveanewheadlineevery10seconds

clock.conf

Theanalogclockisshownatthetop,intheleft-handcornerofthemirrorusingthedemoconfiguration:

[core]

class=AnalogClock#UsingtheAnalogClockwidget

update_interval=1#Clocksmusthavethissetto1second

[ui]

width=200#AnalogClockmustbesettoawidthof200

show_borders=false#AnalogClocklookbetterwithbordersdisabled

[position]

mode=top#Puttheclockinthetopbar

index=0#Thiswillbethefirstitem

[widget]#Donotneedanyconfigurationhere

StylesTheglobalstyleisconfiguredusingthemirror_webapp/static/style.cssstylesheet.Thiscontainsthestylesthatareusedinallotherwidgetsandistheeasiestwaytomakealterationstofontsizesandlayoutmargins.

TipForanyconfigurationthatshouldonlyaffectasinglewidget,thestyle.cssfileforthatspecificwidgetisabetterplacetomakethechange.

Themainsectionsthatyoumaywishtomakealterationstoareasfollows:

Thisdefinesthedefaultstyleforallthetextdisplayedonthemirror,includingthefont.Ifyouwishtouseanalternativefont,thiswouldbetheplacetomakethechange(bydefault,IamusingtheRobotofontbyChristianRobertson):

h1,h2,h3,h4,h5,h6,p,li{

font-family:'Roboto',sans-serif;;

margin:0;

font-weight:normal;

color:#FFF;

}

Thefollowingsetofstylesdefinethesizeofeachofthedifferentlevelsoftext.Bydefault,theyusetheviewportwidthCSSsize:

h1{font-size:5vw;}

h2{font-size:3.75vw;}

h2,h3,h4,h5,h6{font-size:3.25vw;}

p{font-size:2.5vw;}

p.small{font-size:1.8vw;}

li{font-size:2.5vw;}

Inmirror_webapp/templates/mirror.html,youwillalsonoticethefollowinglineatthetopofthepage.ThisisusedtoloadtheRobotofontfromtheGoogleFontservice(www.google.com/fonts):

<linkhref='http://fonts.googleapis.com/css?family=Roboto:400,100'

rel='stylesheet'type='text/css'>

Oncetheconfigurationiscomplete,rebootthePiandyoushouldbegreetedwithyourcustomizedinformationdisplay.

TroubleshootingThissectiondetailssomeofthecommonissuesyoumayencounterwhilebuildingthisprojectandthestepstobetakentoresolvethem.

Forissuesnotlistedhere,checkeitherthelogfilesinthe/home/pidirectory(anditssubdirectories)ortheChromium(orGoogleChrome)developerconsole.

Thewebapplicationfailswiththe500InternalServerErrorThiscanbecausedbyavarietyofreasons.Moreinformationastothecauseoftheproblemwillbeavailableinthe/home/pi/mirror_webapp/mirror_app.loglogfile.

Someofthecommonissuesthatarelikelytocausethisare:

ThelackofInternetconnectionmaycausefailuretoupdatewidgets,suchasweatherandRSSTickerErrorsinwidgetconfigurationfilescancausefailureoftheserver-sidePythonscriptingErrorsinthewidgetcodeitselfwillalsocausethisissue;althoughthisislesslikely

ThedisplaydoesnotworkTherecanbeissueswiththeusageofcertainHDMItoVGAadapterswiththePi.Editthe/boot/config.txtfileanduncommentthefollowingline:

hdmi_force_hotplug=1

ThisforcesthePitooutputthevideoontheHDMIoutputevenifitfailstodetectadeviceconnectedtoit.

Ifyoustillhaveproblemsafterthis,thenthereislikelyanissuewiththepowersupplyyouareusingtopowerthePi.SinceHDMItoVGAadaptersalsodrawpower,alargerUSBpowersupply(preferablycapableofoutputtingupto2A)isneededtoperformstableoperations.

SummaryInthischapter,welookedathowtorunawebapplicationonthePiusingFlaskandPythontocreateaframeworkthatprovidesaneasywaytoaddnewinformationdisplaystothemirrordisplay.

Wealsohadalookatsomemoreadvancedtechniquestomanufactureanenclosure,whichcanbeappliedtoawiderangeofprojectsyoumaywishtopursueafterthisbook.

Inthenextchapter,wewilllookatyetanotherexampleofhowthePicanbeusedtocontrolelectronicdevicesinrealtime,whenwewillbuildanelectronicxylophonethatplaysmusicfromMIDIfiles.

Chapter10.BottleXylophoneInthischapter,wewillbuildaconfigurableMIDI-controlledxylophone-likeinstrumentmadewithemptyglassbottlesandasetofservos.ThiswillmakeuseofalmostallofthePi’sGPIOheaderstodrivetheservos.

TheservosarecontrolledusingawebapplicationthatallowsyoutouploadaMIDIfile,setatemp,andallowsthePitoplaythefileonthebottlesusingaconfigurationfiletotellitwhichbottleistunedtowhichnote.Thetuningitselfisdonebyvaryingthelevelofwaterineachbottle.

SincethisprojectrequiresalotofGPIOpins,youmaywishtooptforaB+model,whichhasanadditionalnineGPIOpinsonits40-pinconnector.

WhatyouwillneedForthisproject,youwillneedthefollowing:

TheRaspberryPiB+AsmallsectionofaprototypingboardUSBpowersupplyandamicroUSBcableHighcurrent5VpowersupplySeveral1000uFcapacitors(www.maplin.co.uk/p/1000f-35v-85c-radial-electrolytic-capacitor-vh51f)Abreadboard(www.maplin.co.uk/p/ad-100-breadboard-ag08j)Astripof0.1-inchpinheaders0.1-inchmale-to-femalepinjumpersM3nutsandmachinescrewsCableties15xemptyglassbottles15xmicroservosA15xservomountbaseA15xservomount

Ifoundthatthelarger500mlbottlesarebetterforthisasopposedtothe330mlones.Anythinglargerthen500mlwillstillwork;however,theymaynotfitontheservomountbasecorrectly(thisshouldnotstoptheservofromworkingcorrectly).

Tomaketuningeasier,itisrecommendedthatyouusethesamesizebottlesforallthe15notes.

Theamountofcapacitorsyouwillneedisdeterminedbythepoweroutputofthepowersupplyyouareusingandthenumberofservosyouhave;atleastfivecapacitorsarerecommendedforthis.Thepowersupplyshouldberatedforatleast2Atoensurereliableoperation.

AssemblinganotebottleThebottlemountsarecomprisedoftwolasercutsectionsof3mmmaterial.Thiscanbeanyrigidmaterial,suchasMDF,plywood,oracrylic.IwouldrecommendyouuseMDF,asitislesspronetodamageunderforceandcanbesandedeasilyifthejointsaretootight.

Thebasedesignhastwolayers,oneforthesectionthatistobecutandasectionthatshowstheroughplacementofthebottles.Thiscanbeengravedifyouwouldlikeitaspartofthe“notebottle”assembly;however,thisisnotrequired.

Thepartsrequiredtoassembleonenotebottle

Theservoarmsthatactuallyhitthebottleswillbemadeusingashortsectionofmetalbar.Thiscanreallybeanymetalbaraslongasalltheservosusethesametypeinordertomaketuningeasier.Todothis,performthefollowingsteps:

1. Thefirststepistocut15lengthsofthemetalbar.Todothis,useapieceofkitchenrolltotightlygripthebarattheedgeofatableandcutasectionaround10cmlongusingahacksaw.

2. Oncethisisdone,youcanthenattachthebarstotheplasticservoarmsthatcamewitheachservo.Todothis,wewillusethearmwithtwolargeservoarmsoppositeeachother(asshowninthefollowingimage)toattachthemetalbartotheservousingtwocableties.

3. Thenextstepistoattachthesmallservomounttothelargermountbase.Youcanattachthemountoneitherofthesetsofthemountingholes;however,youonlyneedtoattachoneservomountperbase.

4. Ifthejointisslack,thenyoucanuseanM3nutandmachinescrewstotightenthejoint.Whetherthisisneededornotdependsontheresolutionofthelasercutterusedtomachinetheparts.Ifthejointfeelsfairlytightonitsown,thenyoucanskipthisstep.

5. Now,allthatisleftistoattachtheservototheservomount.Thiscanbedoneusingeitherthesmallscrewsthatcamewiththeservoorusinganadhesive,suchashotglueorAraldite.

Oncethisisdone,youshouldhaveanotebottleassemblythatlookssimilartotheoneshowninthefollowingimage:

ElectronicsNowthatthenotebottleassemblyisbuilt,itistimetobuildtheelectronicsthatwillconnecttheservostothePi.Thisstepisrelativelysimple,asallthatyouneedtodoisconnectthePidirectlytothesignalwireoftheservos(usuallyyelloworwhite,sometimesorange)andprovidepowertotheservos.

SincethisprojecthasthescopetousealotofGPIOpins,wewillusethePiB+forthisproject,whichhasanadditionalnineusableGPIOpinsonits40-pinheaderthanontheolderPimodelB’s26pinheader.

Forreference,thecircuitwewillconstructislaidoutsimilartothefollowingdiagram(notethatforsimplicity,onlyoneservoisshownhere):

Thefirststeptocreatetheelectronicpartsofthisprojectistobuildapowerdistributionboardthatcanbeconnectedtoalltheservosinordertoreceivepower.ThisboardisverysimilartotheoneusedfortheservosontheroboticarminChapter8,Remote-operatedRoboticArm.Performthefollowingstepstobuildapowerdistributionboard:

1. Takeasectionoftheprototypingboardand0.1-inchpinheadersandsolderthem,asshowninthefollowingdiagram,suchthattherearetwolongstripsofconnectedpins:

Oncethisiscomplete,youshouldhaveaboardthatlookssimilartothis:

2. Ifyourpowersupplyisratedfor3Aorless,youwillmostlikelyneedtoincludeacapacitorbanktoensurethatthereisaconstantreliablepowersupplyforthemotors.Thiscanbebuiltbysimplyconnectingthecapacitorsalongwithoneofthepowerrailsofabreadboard.Usingtwomale-to-femalejumperwires,connectthistotheservopowerdistributionboard.

NoteWhilebuildingthecapacitorbank,ensurethatallthecapacitorsarewiredinthecorrectway.Therewillbealightstripwithseveralnegative(-)symbolsnexttothelegthatmustbeconnectedtotheground.Thislegisalsoshorterthanthepositiveleg.

Ifthistypeofcapacitorisconnectedintheincorrectwayinthecircuit,thenitcanswell,leak,orexplode.

3. Next,wewillconnecteachoftheservostothepowerdistributionboardsuchthatthesignalpinisoverhangingontheedge.Notethatbecauseofthewidthoftheservoheaders,youarebetteroffifyouconnecttheminsetsoffive,asshowninthefollowingimage:

4. Finally,wecanconnecttheservosignalwirestothePi.Thefollowingdiagram

showsthepinsthatareavailableonboththePimodelB(justthepinsabovetheblueline)andthemodelB+(theentireconnector).Inordertousethedefaultconfigurationsuppliedwiththecode,youmusthaveanotebottleonthesepins:4,17,18,27,22,23,24,10,9,25,11,8,7,and5.ThefollowingdiagramshowstheGPIOpinsavailabletoconnecttheservostoandthecommongroundpin:

Oncethisiscompleteandallthebottlesareinplace,thefinishedsetupshouldlooksomethinglikethis:

Ifyoufindthatyoucannotlayouteachofthenotebottlesinaverysuitablewayduetotheshortcablesontheservos,youcanusesomeextensioncablesthatgivearoundanother30cmofcablelength.Suchcablescanbefoundatwww.amazon.co.uk/Remote-Control-Servo-Extension-Cable/dp/B007SUKUXM.

ThewebapplicationAswiththepreviouschapter,thewebapplicationthatcontrolstheservosisbuiltusingtheFlaskframeworkandservedusingNginxandGunicorn.Hence,thedeploymentprocedurewillbeverysimilarhere:

1. First,wemustensurethattheRaspbianinstallationisuptodateandinstallthepackagesthatweneedtodeployonthewebapplication:

sudoapt-getupdate

sudoapt-getupgrade

sudoapt-getinstallpython-pipgitpython-devgunicornsupervisor

nginxswiglibasound-dev

sudopipinstallRPIO

2. Next,wewillclonethecoderepositoryfortheMIDIparsinglibrarythatwillbeusedtoreadMIDIfilesandtheninstallitusingPythonsetuptools:

gitclonehttps://github.com/vishnubob/python-midi.git

cdpython-midi

sudopythonsetup.pyinstall

cd

3. Next,wewillclonethecoderepositoryfortheFlaskframeworkandinstallitusingPythonsetuptools:

gitclonehttps://github.com/mitsuhiko/flask.git

cdflask

sudopythonsetup.pyinstall

cd

4. Next,wewillcopytheNginxconfigurationfilesfromtheprojectfoldertotheconfigurationdirectories;wewillhaveNginxverifytheconfigurationandapplytheconfigurationbyrestartingtheNginxservice:

sudocpconfig_files/nginx/bottle_xylophone.conf/etc/nginx/sites-

available/bottle_xylophone.conf

sudoln-s/etc/nginx/sites-available/bottle_xylophone.conf

/etc/nginx/sites-enabled/

sudorm/etc/nginx/sites-enabled/default

sudonginx-t

sudoservicenginxrestart

5. Now,wewillcopythesupervisorconfigurationandhavethesupervisorrereaditsconfigurationfiles:

sudocpconfig_files/supervisor/bottle_xylophone_webapp.conf

/etc/supervisor/conf.d/bottle_xylophone_webapp.conf

sudosupervisorctlreread

6. Next,wewillcopythewebapplicationconfiguration,whichwillbereadbyourwebapplication.Itcontainstheconfigurationfortheservooutput:

cpconfig_files/bottle_xylophone.conf~

7. Finally,wewillupdatethesupervisorandstartthewebapplication:

sudosupervisorctlupdate

sudosupervisorctlstartbottle_xylophone_webappp

Nowthatthewebapplicationhasbeendeployed,youshouldbeabletobrowsetotheapplicationusingtheIPaddressofthePifromaPConthesamenetworkasthePi.Whenyoudoso,youshouldseeapagesimilartothefollowing:

ConfigurationChancesarethatthePiandbottleswillneedtobereconfiguredandretunedonapersongbasisduetothelimitednumberofnotesthatcanbeconfiguredatthesametime(ifyouusethePimodelB+,thismaynotbeabigproblem).Tohelpmakethisprocesseasier,thereisascript(midi_note_summary.py)includedwiththischapterthatwilltakeaMIDIfileandgenerateareportofexactlywhatnotesareusedinthefile.ThiswillmakeiteasierforustodeterminewhichnoteshavetobeconfiguredonthePiandaccordingly,thebottlescanbetunedforthem.

Thisscriptshouldbeusedwiththefollowingcommand,whereMIDI_FILEisthefilenameoftheMIDIfile:

pythonmidi_note_summary.pyMIDI_FILE.mid

Itsoutputisshowninthefollowingscreenshot:

NotethatthisscriptwillworkstraightawayonthePiwithoutadditionalconfiguration,asalltherequiredlibrariesareinstalledwhenthewebapplicationisdeployed.However,tousethescriptonadifferentPC,youwillfirsthavetodownloadandinstallthepython-midilibrary(https://github.com/vishnubob/python-midi).

Onceyouhavedeterminedtherangeofnotesthatareneededforaparticularsong,youcanthenmodifythebottle_xylophone.confconfigurationfiletosettheGPIOpinsthatwillbeusedforeachMIDInote.

Thisfilemustfirstcontaintwosettingsthatdeterminetheservotimingoutputvaluesthatcorrespondtotheretractedposition(whichtheservoisinwhenitisnotbeingused)andhitposition(thepositionatwhichtheservoarmwillhitthebottle).Thesesettingswillbeappliedtoalltheconfiguredservosunlessstatedotherwisewithaservo-specificconfiguration:

DEFAULT_HIT=1700

DEFAULT_RETRACT=1500

ThefollowingsectionoftheconfigurationfileshouldnowcontainthemappingbetweentheMIDInoteandGPIOnumber.Thegeneralformatforthisisasfollows:

MIDI_GPIO_[NOTE]=[GPIO]

Here,[NOTE]istheMIDInotenumberand[GPIO]istheGPIOnumber.Anexampleofhownotesshouldbemappedisshownasfollows:

MIDI_GPIO_49=4

MIDI_GPIO_50=17

MIDI_GPIO_51=18

MIDI_GPIO_53=27

Inthecasewhereaparticularservohasdifferenthitandretractpositionsfromtheothers(forexample,becauseofadifferentsizedbottleorservoarm),thiscanbeconfiguredusingthegeneralformat:

MIDI_HIT_[NOTE]=[SERVOOUTPUT]

MIDI_RETRACT_[NOTE]=[SERVOOUTPUT]

Here,[NOTE]istheMIDInotenumberand[SERVOOUTPUT]istheservotimingvaluetotheoutput.Anexampleofthisisshownasfollows:

MIDI_HIT_49=1800

MIDI_RETRACT_49=1550

MIDI_HIT_50=1850

Onceyouhaveconfiguredthewebapplication,itisworthchangingthedefaultloglevelfromDEBUGtoeitherINFOorWARNINGtoreducetheamountofinformationthatissavedtothelogfile.Thiscanbedoneusingthefollowingentryintheconfigurationfile:

LOG_LEVEL=[LOGLEVEL]

Here,[LOGLEVEL]iseitherINFOorWARNING.

Whenyouarefinishedmakingchangestotheconfigurationfile,makesuretoreloadthewebapplicationusingthefollowingtwocommands:

sudosupervisorctlstopbottle_xylophone_webapp

sudosupervisorctlstartbottle_xylophone_webapp

TuningTogetassistancefortuningthebottles,itisbesttouseatonegeneratortogetanideaofthesoundyouareaimingforwhenyoustrikethebottles.Theseareavailableinmanyforms;onegoodwebsitethatdoesthisishttp://plasticity.szynalski.com/tone-generator.htm,whichallowsyoutoselectanynoteandplayasampleofit.Audacity(http://audacity.sourceforge.net/)isanexampleofapieceofdesktopsoftwarethatdoesasimilarthing.Therearealsomanysmartphoneapplicationsthathavesimilarfeatures.

Thefirststeptotuneasetofbottlesistosortthebottlesintogroupsofuniquecombinationsofshapesandsizes.Thecombinationofthesetwopropertieswilldefinethepitchofthesoundabottlewithoutanyliquidmakeswhenitisstruck(thefrequencyofwhichisknownasthebottle’snaturalfrequency,thatis,thefrequencyatwhichitwilloscillatewhennotexposedtoexternaldampening).Wewillthenusethebottleswiththelowestpitchforthelower-pitchedMIDInotesandviceversa.

Onceyouhaveasourceoftheactualnoteyouareaimingfor,yousimplyhavetohiteachnotewithoneoftheservoarms(detachedfromtheservoitself)andchangethelevelofwaterinthebottleuntilthenotesoundssimilartothetargetnote.

TestingNowthatwehavefinishedbuildingthebottlexylophone,itistimetogiveitatestusingaMIDIfile.First,browsetotheIPaddressofthePiandyoushouldbegreetedwithapagesimilartothefollowing:

Towardthebottomofthepage,youwillhavetheoptiontobrowseforaMIDIfile(withthe.midfileextension)andtouploadit.Onceyouhavedoneso,youwillseethefilelistedintheMIDIFilessectionofthepageaswellasaconfirmationmessagethatthefilewassuccessfullyuploaded,asshowninthefollowingscreenshot:

Ifrequired,thetempoatwhichthefilewillbeplayedcanbemodifiedusingthetemposettingatthetopofthepage.ThismustbesetbeforeyouselectafiletobeplayedbychangingthevalueinthefieldandbyclickingonSubmit.Oncethetempohasbeenchanged,youwillseeanotification,asshowninthefollowingscreenshot:

Onceyouarereadytoplayafile,simplyclickonthe[play]linknexttothefilename.Youshouldseeanotification,asshowninthefollowingscreenshot,andtheservosshouldstarttomove.Ifyouhaveanyissueshere,refertotheTroubleshootingsectionlaterinthischapter.

Playbackcanthenbestoppedusingthe[stop]linknearthetopofthepage.

TroubleshootingThissectiondetailssomeofthecommonissuesyoumayencounterwhilebuildingthisprojectandstepsyoucanusetoresolvethem.

NotesaremissedThemostcommoncauseofmissednotesisthedelaybetweenthenoteoneventandnoteoffeventintheMIDIfile.IftheMIDIfileistooshort,itwillnotgivetheservoarmtimetoextendandretract.Thiscanberectifiedusingthemidi_note_expand.pyscriptincludedinthecodeforthischapter.

Thisscriptcanberunusingthefollowingcommand;here,MIDI_FILEisthefilenameoftheMIDIfile,DELAYisthedesiredminimumdelayinmillisecondsbetweennoteonandnoteoffevents,andTEMPOisthetempoyouintendtoplaythefileat(thedelaytimewillvarydependingonthetempoatwhichthefileisplayed):

pythonmidi_note_expand.py-fMIDI_FILE.mid-dDELAY-tTEMPO

Thisscriptwillproduceanoutputsimilartothatshowninthefollowingscreenshot.Bydefault,itsavesthemodifiedfileasMIDI_FILE_modified.mid.Bydefault,thescriptwillonlymodifythedelaybetweenthenotesifitislessthanthevaluesetusingthe-dparameter.Thescriptcanalsobeusedtosetthedelaybetweennoteeventsforallthenotesinthefiletothesamevaluebyaddingthe-sflagtotheendofthecommand.

ServosdonotmovecorrectlyIftheservosseemtobebehavingerratically,thenthereisalmostcertainlyanissueregardingalackofsufficientpowersupplyforalltheservos.Thiscanbeconfirmedbymeasuringthevoltageacross5Vandgroundconnectionsontheservopowerdistributionboard.

SummaryInthischapter,wecontinuedtolookatthepossibilitiestocontrolhardwareusingtheGPIOportsandhadaquicklookattheadditionalfeaturesofthePimodelB+.

Wealsolookedatsomeoftheissuescausedbydrivinglargenumbersofelectronicdevicesthatrequirealargeamountofpowerduringtheiroperations.Wealsolookedathowtheseissuescanbeovercome.

Nowthatyouhavecompletedalltheprojectsinthisbook,itistimeforyoutoembarkonyourownprojectsusingtheRaspberryPiandthevastrangeofdevicesthatcanbeusedwithittocreatesomeimpressiveprojectsthatcaninteractwiththeworldaroundyou.

IndexA

AdafruitURL/UsingthebuttonsandjoystickwithPiPlay

AllThingsPiURL/InstallingLogitechMediaServer

Arduinosettingup,forMaplinsensors/SettingupyourArduinosettingup,forRFnetwork/SettingupArduino

ArduinoIDEURL/SettingupyourArduino

AudacityURL/Tuning

Bbottlexylophone

requisites/Whatyouwillneednotebottle,assembling/Assemblinganotebottleelectronics,configuring/Electronicswebapplication,creating/Thewebapplicationconfiguration/Configurationtuning/Tuningtesting/Testingtroubleshooting/Troubleshooting

Ccalibration,roboticarm

chassismotors/Chassismotorsarm2/Arm2andhandservoshandservos/Arm2andhandservosarm1servos/Thearm1servos

camerasettingup,forroboticarm/Settingupthecamera

CameraSerialInterface(CSI)about/Settingupthecamera

captures,GPS-enabledTimelapseRecorderusing/Usingthecapturestimelapsevideo,creating/Creatingatime-lapsevideoGPSdata,exportingasCSV/ExportingGPSdataasCSV

capturesoftware,GPS-enabledTimelapseRecordersettingup/Settingupthecapturesoftware

Chromiumsettingup/SettingupChromium

closureabout/TheJavaScriptcode

comma-separatedvalue(CSV)fileabout/ExportingGPSdataasCSV

configuration,MagicMirrorwidget/Widgetsstyles/Styles

CoreutilsViewerURL/LinuxandMacOS

DDocumentObjectModel(DOM)

about/TheJavaScriptcodedriveelectronics

configuring,forroboticarm/Driveelectronics

Eelectronics,PortableSpeakerSystem

building/Buildingtheelectronicsamplifiercircuit,connecting/Theamplifiercircuitbattery,using/Runningthespeakersystemonbatterypower

enclosureconstruction,MagicMirrorinstructions/Enclosureconstructionwithoutplywoodenclosure/BuildingthemirrorwithoutanenclosurePienclosure/ThePienclosureURL,forPienclosure/ThePienclosure

extensioncablesreferencelink/Electronics

FFileZilla

URL/TransferringMP3filestothePiFlask

URL/Theweatherstationwebapplication

GGoogleChartsAPI

URL/TheweatherstationwebapplicationGoogleFonts

URL/StylesGPS-enabledTimelapseRecorder

requisites/Whatyouwillneedhardware,settingup/Settingupthehardwarecapturesoftware,settingup/Settingupthecapturesoftwarecaptures,using/Usingthecaptures

GunicornURL/Theweatherstationwebapplication

HHackspaces

about/Whatyouwillneedhardware,GPS-enabledTimelapseRecorder

settingup/Settingupthehardwarecameraboard/Thecameraboardcameramodule,connectingtoRaspberryPi/ConnectingthecameramoduletothePiRaspberryPicamera,settingup/SettinguptheRaspberryPicameraGPSmodule,settingup/TheGPSmodule

homesecuritysystemrequisites/Whatyouwillneedstructure/Thesecuritysystemstructuredesigning/Designingyoursecuritysystemwebapplication,creating/Webapplicationssensors,interfacing/InterfacingsensorsRFnetwork/TheRFnetworktroubleshooting/Troubleshooting

hometheatrePCrequisites/WhatyouwillneedOpenELEC,settingup/SettingupOpenELECLCD,settingup/SettinguptheLCDswitches,settingup/Settinguptheswitchesassembling/Finalassembly

Iinstallation,LogitechMediaServer

about/InstallingLogitechMediaServer

JJavaScriptdevelopment

referencelink/TheJavaScriptcodeJavaScriptObjectNotation(JSON)

about/ThePythoncodeJinjatemplatelanguage

referencelink/TheJinjapagetemplate

LLCD

settingup/SettinguptheLCDLCDconfigurationfiles

referencelink/SettinguptheLCDLCDproc

about/SettinguptheLCDlight-dependentresistor(LDR)

about/UnderstandingthesensorsLinux

SDcard,writing/LinuxandMacOSLinuxdistribution

selecting,forRaspberryPi/ChoosingaLinuxdistributionLinuxshellcommands

cd/CommonLinuxcommandsls/CommonLinuxcommandsmkdir/CommonLinuxcommandscat/CommonLinuxcommandspwd/CommonLinuxcommandschmod/CommonLinuxcommandssudo/CommonLinuxcommandsmv/CommonLinuxcommandscp/CommonLinuxcommandsrm/CommonLinuxcommands

LogitechMediaServersettingup/SettingupLogitechMediaServerrunning/RunningLogitechMediaServeronthePibackupimage,creatingofSDcard/CreatingabackupimageofanSDcardUSBstoragedevice,automounting/AutomountingaUSBstoragedeviceinstalling/InstallingLogitechMediaServerPi,settingupasWi-Fiaccesspoint/SettingupthePiasaWi-Fiaccesspoint

MMacOS

SDcard,writing/LinuxandMacOSMagicMirror

requisites/Whatyouwillneedrequiredtools/Toolsyouwillneedtheory/Theorywebapplication,developing/ThewebapplicationPisetup/ThePisetupenclosure,constructing/Enclosureconstructionconfiguration/Configurationtroubleshooting/Troubleshooting

magneticdoorsensorsusing/Magneticdoorsensors

Maplinsensorsusing/ReverseengineeringtheMaplinsensorsworkingwith/Understandingthesensorswiring/WiringArduino,settingup/SettingupyourArduino

measurementunitsforwindspeed/Usingthewebapplicationfortemperature/Usingthewebapplicationforhumidity/Usingthewebapplicationforpressure/Usingthewebapplicationforlightlevelandrain/Usingthewebapplication

mediafilestypes/UploadingmediafilestothePi

mediaplayerscripting/ScriptingamediaplayerPiFM,callingfromPython/CallingPiFMfromPythonMP3files,searching/SearchingforMP3filesinput,obtainingfromcommandline/Gettinginputfromacommandlinemediafiles,queuing/Queuingthemediafilestobeplayedplayer.pyscript,using/Usingthemediaplayerscript

mediumdensityfiberboard(MDF)about/Buildingtheenclosureforthespeakersystem

milesperhour(MPH)about/Understandingthesensors

MinibianURL/ChoosingaLinuxdistribution

miniretro-stylearcadecabinetrequisites/Requirementsinputelectronics,settingup/Settinguptheinputelectronics

cabinet,building/Buildingthecabinetreferencelink/BuildingthecabinetPiPlay,settingup/SettingupPiPlaybuttons,usingwithPiPlay/UsingthebuttonsandjoystickwithPiPlayjoystick,usingwithPiPlay/UsingthebuttonsandjoystickwithPiPlay

miniretro-stylearcadecabinet,requisiteshardware/Requirementstools/Requirements

mountpointabout/Linux

MP3filestransferring,toRaspberryPi/TransferringMP3filestothePi

Nnetwork

scanning,withNmaputility/NetworkscanningNginx

URL/TheweatherstationwebapplicationNmaputility

URL/Networkscanningused,forscanningnetwork/Networkscanning

OOnlineToneGenerator

URL/TuningOpenELEC

settingup/SettingupOpenELECbooting/ThefirstbootandinitialsetupPi,connectingtowirelessnetwork/ConnectingthePitoawirelessnetworkmediafiles,uploadingtoPi/UploadingmediafilestothePimediafiles,uploadingonWindows/Windowsmediafiles,uploadingonLinux/LinuxPi,shuttingdown/ShuttingdownthePi

outdoorweatherstationrequisites/WhatyouwillneedMaplinsensors,using/ReverseengineeringtheMaplinsensorssensors,settingup/Settinguptheremainingsensorsweatherstationwebapplication,creating/Theweatherstationwebapplicationassembling/Assemblingtheweatherstationusing/Usingthewebapplication

PPiPlay

URL/SettingupPiPlaysettingup/SettingupPiPlaybuttons,using/UsingthebuttonsandjoystickwithPiPlayjoystick,using/UsingthebuttonsandjoystickwithPiPlay

PirateRadiosettingup/SettingupthepirateradioMP3files,transferringtoRaspberryPi/TransferringMP3filestothePi

PIRmotionsensorsusing/ThePIRmotionsensors

Pisetup,forMagicMirrordisplay,rotating/Rotatingthedisplaywebapplication,deploying/DeployingthewebapplicationChromium,settingup/SettingupChromium

PortableSpeakerSystemrequisites/Whatyouwillneedrequiredtools/ToolsyouwillneedLogitechMediaServer,settingup/SettingupLogitechMediaServerRaspberryPi,settingasSqueezeboxclient/SettingupthePiasaSqueezeboxclientelectronics,building/Buildingtheelectronicsenclosure,building/BuildingtheenclosureforthespeakersystemLogitechMediaServer,runningonPi/RunningLogitechMediaServeronthePi

potentialdividerabout/Understandingthesensors

printedcircuitboard(PCB)about/Understandingthesensors

prototypingboardabout/SettinguptheLCD

pull-upresistorabout/Understandingthesensors

PulseWidthModulation(PWM)about/Driveelectronics

push-to-make(PTM)buttonsabout/Whatyouwillneed

PuTTYURL/ConnectingtothePiviaSSH

python-midilibraryURL/Configuration

PythonSMTPlibraryURL/Deployingourapplication

RRaspberryPi

settingup/SettingupthePiLinuxdistribution,selecting/ChoosingaLinuxdistributionURL,fordownloading/ChoosingaLinuxdistribution,WritinganSDcardSDcard,writing/WritinganSDcardbooting/BootingthePiforthefirsttimenetworkscanning,withNmaputility/Networkscanningconnecting,viaSSH/ConnectingtothePiviaSSH,CommonLinuxcommandsinitialsetup/TheinitialsetupMP3files,transferring/TransferringMP3filestothePisettingup,forRFnetwork/SettinguptheRaspberryPi

RaspberryPi,asSqueezeboxclientsettingup/SettingupthePiasaSqueezeboxclientWi-Fi,settingup/SettingupWi-FionthePisqueezelite,runningasdaemon/Runningsqueezeliteasadaemon

remotecontrolfunctionsInput.Up/SettinguptheswitchesInput.Down/SettinguptheswitchesInput.Left/SettinguptheswitchesInput.Right/SettinguptheswitchesInput.Select/SettinguptheswitchesInput.Back/SettinguptheswitchesInput.Home/SettinguptheswitchesPlayer.PlayPause/SettinguptheswitchesPlayer.Stop/SettinguptheswitchesPlayer.GoPrevious/SettinguptheswitchesPlayer.GoNext/Settinguptheswitches

residualcurrentdevice(RCD)about/Buildingtheenclosureforthespeakersystem,Buildingthecabinet,Enclosureconstruction

revolutionsperminute(RPM)about/Understandingthesensors

RF24NetworklibraryURL/TheRFnetwork

RFnetworkusing/TheRFnetworkRaspberryPi,settingup/SettinguptheRaspberryPiArduino,settingup/SettingupArduino

RH(relativehumidity)about/Whatyouwillneed

roboticarmrequisites/Whatyouwillneed

driveelectronics,configuring/Driveelectronicscamera,settingup/Settingupthecamerawebapplication,deploying/Deployingwebapplicationsarm,constructing/Thearmandchassisconstructionchassis,constructing/Thearmandchassisconstructioncalibrating/Calibrationtroubleshooting/Troubleshooting

Sscheduledoperatingsystem

about/UnderstandingthesensorsSDcard

writing/WritinganSDcardwriting,onWindows/Windowswriting,onLinux/LinuxandMacOSwriting,onMacOS/LinuxandMacOSbackupimage,creating/CreatingabackupimageofanSDcard

SecureFileTransferProtocol(SFTP)about/TransferringMP3filestothePi

sensorssettingup/SettinguptheremainingsensorsDHT11/22,settingup/DHT11/22BMP180,settingup/BMP180readings,recording/Takingreadingsfromthesensors

sensors,homesecuritysysteminterfacing/InterfacingsensorsPIRmotionsensors,using/ThePIRmotionsensorsmagneticdoorsensors,using/Magneticdoorsensors

servicesetidentifier(SSID)about/SettingupWi-FionthePi

squeezeliteURL/SettingupthePiasaSqueezeboxclientrunning,asdaemon/Runningsqueezeliteasadaemon

SSHRaspberryPi,connecting/ConnectingtothePiviaSSH,CommonLinuxcommands

SupervisorapplicationURL/DeployingtheapponthePi

switchessettingup,forhometheatrePC/Settinguptheswitches

Ttroubleshooting,bottlexylophone

missednotes/Notesaremissedservosmovement/Servosdonotmovecorrectly

troubleshooting,MagicMirrorissues,withwebapplication/Thewebapplicationfailswiththe500InternalServerErrordisplayissue/Thedisplaydoesnotwork

troubleshooting,roboticarmvideostream/Thevideostreamhasasubstantialdelayservos/Theservosmakealoudhummingnoiserobotcontrol/Controloftherobotislostarmsmovement/Thearmjumpstonewpositions

Uultracabs

about/SettinguptheinputelectronicsURL/Settinguptheinputelectronics

USBstoragedeviceautomounting/AutomountingaUSBstoragedevice

VVideoforLinux2(V4L2)driver

about/Settingupthecamerareferencelink/Settingupthecamera

Wweatherstationwebapplication

creating/Theweatherstationwebapplicationdeploying/DeployingtheapponthePi

webapplication,homesecuritysystemcreating/Webapplicationsdeploying/Deployingourapplicationsensors,configuring/Configuringsensorsandalarmsalarms,configuring/Configuringsensorsandalarms

webapplication,MagicMirrordeveloping/Thewebapplicationwidget,developing/Developinganewwidget

Wi-Fisettingup,onRaspberryPi/SettingupWi-FionthePireferencelink/SettingupWi-FionthePi

widget,MagicMirrorPythoncode/ThePythoncodeJinjapagetemplate/TheJinjapagetemplateJavaScriptcode/TheJavaScriptcodeconfigurationfiles/Widgets,Exampleconfigurationsconfigurationoptions/Includedwidgets

widgetconfiguration,MagicMirrorbbc_ticker.conffile/bbc_ticker.confclock.conffile/clock.conf

Win32DiskImagerURL/Windows

WindowsSDcard,writing/Windows

XXBMCmediacentersoftware

URL/SettingupOpenELEC

Z7-Zip

URL/SettingupOpenELEC