University of Bordeaux

IMSAT option

INTERNSHIP REPORT :

EDISON Electronics,a design and assembly company of printed

circuit boards

Gemma PRIETO AGUILAR

14 February 2015

Name of university tutor: Christophe FargesName of organism tutor: ngel Martnez Cereza

Acknowledgements

All the special thanks goes out to my Edison colleagues, whose courage,

smiles, laughs and advice have been the greatest values and lessons I took

from this company.

Contents

1 Introduction 5

2 EDISON Electronics... 62.1 ... a family business. . . . . . . . . . . . . . . . . . . . . . . . 62.2 ... a company focused on SMD. . . . . . . . . . . . . . . . . . 6

2.2.1 What is SMD? . . . . . . . . . . . . . . . . . . . . . . 62.2.2 PCB, the base of an electronic circuit . . . . . . . . . . 92.2.3 Design and assembly stages . . . . . . . . . . . . . . . 12

3 Apprentice in Edison 183.1 Assembly stage . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.1.1 Welding task . . . . . . . . . . . . . . . . . . . . . . . 183.1.2 Attach task . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2 Programming stage . . . . . . . . . . . . . . . . . . . . . . . . 203.2.1 Microcontroller programming task . . . . . . . . . . . . 203.2.2 Recording task . . . . . . . . . . . . . . . . . . . . . . 20

3.3 Test stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.3.1 Test procedure . . . . . . . . . . . . . . . . . . . . . . 213.3.2 Repairing task . . . . . . . . . . . . . . . . . . . . . . . 22

4 Programming a microcontroller 234.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1.1 Whats SCI? . . . . . . . . . . . . . . . . . . . . . . . . 244.1.2 Project objective . . . . . . . . . . . . . . . . . . . . . 24

4.2 Programming with CodeWarrior . . . . . . . . . . . . . . . . . 244.2.1 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 244.2.2 Programme created . . . . . . . . . . . . . . . . . . . . 254.2.3 Hyperterminal . . . . . . . . . . . . . . . . . . . . . . . 26

4.3 A Visual Basic Interface . . . . . . . . . . . . . . . . . . . . . 26

5 Conclusion 28

List of Tables

2.1 A PCB example with n layers. . . . . . . . . . . . . . . . . . 9

List of Figures

2.1 Surface-mount components on a USB flash drives circuit board. 72.2 A diagram showing how a through-hole mounted component

is inserted into a PCB prior to soldering. . . . . . . . . . . . . 82.3 This electronic circuit contains, mostly, SMD components:

resistors, transistors... but also some THT components: a(brown) transformer, a (blue) capacitor or the (white) plugs. . 8

2.4 (a) Soldermask and (b) Silkscreen . . . . . . . . . . . . . . . . 102.5 SMD and tru-hole pads. Components IC1 and R1 contains

8 and 2 SMD pads respectively, Q1 and PW 3 tru-hole padseach one. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.6 Schema showing a PCB with 2 (left) and 6 internal layers(right), alternated with the B stage and a non-conductivematerial, epoxy glass. . . . . . . . . . . . . . . . . . . . . . . . 11

2.7 Double-sided PCB with and without PTH . . . . . . . . . . . 122.8 Current process in PCB design . . . . . . . . . . . . . . . . . 132.9 PCB schema . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.10 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.11 One of the two Edisons pick and place machines . . . . . . . . 16

3.1 Tin crossing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.2 Weldering steps . . . . . . . . . . . . . . . . . . . . . . . . . . 193.3 Apprentice assembling components . . . . . . . . . . . . . . . 203.4 A Freescale recorder programming a PCB . . . . . . . . . . . 213.5 A PCB passing a test procedure . . . . . . . . . . . . . . . . . 22

4.1 MC9S08SH32 of freescale . . . . . . . . . . . . . . . . . . . . . 234.2 Hyperterminal returns 1 when Switch 1 is pressed. . . . . . . 264.3 Hyperterminal returns a ASCII value every time the wheel of

A/D converter is moved . . . . . . . . . . . . . . . . . . . . . 274.4 Interface with an open failure of serial port . . . . . . . . . . . 27

Chapter 1

Introduction

As part of my formation in GSAT, I have had the opportunity to do aninternship, in a company called Edison Electronics in Barcelona. Theinternship duration was of 10 weeks in which the company proposed to methe following objectives and tasks:

1. Learn the different electronic components used in a printed circuitboard (PCB)

2. Learn to assembly these components

3. Testing and repairing PCBs.

4. Observe and assist in the design of a PCB

5. Visual verification of PCBs

From all these objectives, I expected to consolidate a good base in electroniccircuits and be able to apprehend electronics components unknown to me.

In this report, first, I will present you this company and the context ofa electronic business, then the different activities I have done like apprenticein Edison, and finally a conclusion.

5

Chapter 2

EDISON Electronics...

2.1 ... a family business.

Edison Electronics is a printed circuit board company set up in 1995 inBadalona (Barcelona) by an electronic engineer, ngel Martnez Cereza. Inthe last 20 years, this Catalan engineer has counted on the help of his wife,and later on his two new graduate electronic engineer sons. Currently, thisbusiness is composed of 5 family members and 4 operators. Since its founda-tion, Edison has specialized on design, assembly, start-up and maintenanceof printed circuit boards (PCB).

2.2 ... a company focused on SMD.

2.2.1 What is SMD?

Surface-mount technology (SMT) is a method for producing electroniccircuits in which the components are mounted or placed directly onto thesurface of printed circuit boards (PCBs). An electronic device so made

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Figure 2.1: Surface-mount components on a USB flash drives circuit board.

is called a surface-mount device (SMD).In the industry it has largelyreplaced the through-hole technology (THT) construction method offitting components with wire leads into holes in the circuit board, as showsFigure 2.2.

Both technologies can be used on the same board for components notsuited to surface mounting such as large transformers and heat-sinked powersemiconductors.

Although both technologies, SMT and THT, have their own advantages,the SMT has very interesting advantages compared with THT: Smaller com-ponents, lower initial cost and time of setting up for production, simpler andfaster automated assembly, better mechanical performance under shake andvibration conditions, etc. But also some disadvantages: manual prototypesand reparations are expensive and difficult, etc.

After presenting the two main types of components used in electroniccompanies like EDISON, it is essential to mention the different phases whichare necessary to obtain our electronic circuit.

But first, lets talk about another indispensable component: the printedcircuit board (PCB).

7

Figure 2.2: A diagram showing how a through-hole mounted component isinserted into a PCB prior to soldering.

Figure 2.3: This electronic circuit contains, mostly, SMD components: resis-tors, transistors... but also some THT components: a (brown) transformer,a (blue) capacitor or the (white) plugs.

8

Layer Position Layer description1 Top silkscreen/overlay2 Top soldermask3 Top paste mask4 Layer 15 Substrate6 Layer 2... ...n Layer n

n+1 Bottom paste maskn+2 Bottom solder maskn+3 Bottom silkscreen/overlay

Table 2.1: A PCB example with n layers.

2.2.2 PCB, the base of an electronic circuit

A definition of PCB could be: Non-conductive substrate board which is usedlike mechanical support to electrically interconnect electronic components,through paths and tracks of a conductive material (copper) etched onto thisnon-conductive substrate".

Components of a PCB are, so:

1. A board, made of a non-conductive material, and

2. Conductive tracks, pads, and others features etched from coppersheets laminated onto this board.

Nowadays, PCBs classification is based on number and type of layers(stuckup), and connexion type between layers.

We could start by listing layers depending if these are conductive or not.In order to understand this, lets consider the PCB example of the Table 2.1.The different layers we could find are:

1. Top Silkscreen/overlay : Its the layer printed over the "Solder-mask" and which contains information leading to facilitate the assemblywork and subsequent verification, as for example, component position,

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Figure 2.4: (a) Soldermask and (b) Silkscreen

orientation and reference, or other kind of information like product andcompany name (Figure 2.4).

2. Top soldermask : Assembly process require use of welding to fixcomponents to the board. To prevent welding accidents such as short-circuits of two different nodes tracks, a soldermask is used. This sol-dermask is a varnish applied to PCB which, usually, is green, but alsored or blue (Figure 2.4).

3. Top paste mask : This layer is formed by pads and tracks.

(a) A pad is a cooper surface on a PCB allowing welding componentsto the board. There are two types of pads: thru-hole and SMD(surface mount) (Figure 2.5).

i. The thru-hole pads are designed to introduce the pin of thecomponent and then weld it on the opposite side which wasintroduced. This type of pads is very similar to a thru-holevia.

ii. The smd pads are designed for surface mounting, ie weld com-ponent on the same side of the board where it was placed.

(b) A track is a copper conductive path for connecting a pad (wherelies the pin or terminal of a component) to another pad. Thetracks may be of different width depending on the currents flowingthrough them (Figure 2.4).

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Figure 2.5: SMD and tru-hole pads. Components IC1 and R1 contains 8 and2 SMD pads respectively, Q1 and PW 3 tru-hole pads each one.

Figure 2.6: Schema showing a PCB with 2 (left) and 6 internal layers (right),alternated with the B stage and a non-conductive material, epoxy glass.

4. Internal layers : Some PCBs contains internal layers (etched cooper)alternated with finest substrate sheets and layers of insulating materialknown as prepreg (or B stage). These sheets are pressed togetherto form a kind of PCBs called "multi-layers PCB". Multi-layer PCBhas facilitated downsizing, weight and volume of systems by allowing inhigher packing density and interconnection. Figure 2.6 shows a schemaof two multi-layer PCBs.

Its very important to clarify multi-layers PCB are not always used. PCBswithout internal layers are still used. Actually, we can explain them bymaking a PCB classification based on components interconnection.

1. Single-sided Printed Circuit Boards : Interconnection of elementsis done by the solder side, components are placed on the other side ofthe substrate.

2. Double-sided Printed Circuit Boards : Interconnection of ele-

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Figure 2.7: Double-sided PCB with and without PTH

ments is done by both faces of substrate. Generally, a face is for weld-ing and the other one for components. Double-sided PCB can be withand without PTH (Figure 2.7).

PTH means plated through-hole connection, and its also used inmulti-layer PCBs. PTH allows interconnect 2 layers by metallizingthe walls of holes in the substrate.

2.2.3 Design and assembly stages

Since a costumer express a bill specifications to a electronic company likeEdison, until this customer receive their electronic circuits, a number ofstages must be completed.

Design stage

Design is one of the most complicated and expensive phases, which requiresthe work of engineers. Unfortunately, I didnt get to see design stage inEdison Electronics, but I will present, succinctly, how this stage devel-ops.

CAD tools (Computer Aided Design) are used in all design stage, andnot just in creation of circuit schemas. CAD tools allow users to simulate

12

Figure 2.8: Current process in PCB design

product functioning without needing to assembly it; with this lowering finalcost.

Figure 2.8 shows all design process, since pattern is not ended until aprototype works.

1. Library components : Before creating a schematic and PCB layoutits necessary to ensure that all components stored in a library withtheir schema and footprint. If not, it would be necessary to createa library and make symbol and footprint design of each componentmissing.

2. Schematic design : It is the process of description in which bill spec-ifications are translated into a schema of electrical components (fromlibraries) and their interconnections (Figure 2.9).

3. Layout design : A Layout (Figure 2.10) is a drawing where electroniccomponents appears with their respective footprints in the positionsthey will occupy in the final PCB, and with interconnection betweencomponent pins (routing).

4. Gerbers generation : Information is sent to PCB manufacturer in aspecial files named Gerbers. Its a format file which contains geometricinformation of different layers of PCB.

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Figure 2.9: PCB schema

Figure 2.10: PCB layout

14

CAD tools contains controllers called ERC (Electric Rules Chek) andDRC (Design Rule Check). These controllers can detect potential designerrors.

After a simulation of our PCB, a prototype is done and tested. If no erroris detected, product manufacturing can start.

Manufacturing stage

In Edison Electronics, PCB manufacturing is subcontracted to anothercompany. After engineers sent Gerbers files to this company, PCBs arriveready to be assembly.

Assembly stage

Once PCBs arrive at Edison, these are ready to be assembled.

1. Through hole assembly : This process can be manual or automatic.Components assembly is done inserting their pins through PADs, andthen fixing them, electrically and mechanically, to PCBs with welding.

This technique usually requires manual welding components, since it isdifficult to automate process of inserting components. However, a ma-chine called Wave Solder is often used to reduce welding time process.

2. SMD assembly : This technique is used especially in automated pro-cess through pick and place systems.

First of all, PCBs must pass by a solder paste printer. This has 2 basicfunctions: to facilitate SMD soldering, and to make a interconnectionof holes and tracks of different layers.

After that, PCBs are introduced in a pick and place system, whichautomatically take components from their packing and placed in pro-grammed coordinates (Figure 2.11).

Finally, PCBs are introduced in a SMD oven where components arefixed.

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Figure 2.11: One of the two Edisons pick and place machines

Generally, PCBs are composed of both components, Through hole andSMD. The order assembly is as follows: First, a PCB is inserted in a solderpaste printer, after SMD is assembled in a pick and place machine, andfixed in a SMD oven. At this moment, these are revised to solve frequentlyproblems like crossing weldings. If the PCB is a Double-sided board, then thisprocess is repeated twice. Through hole assembly starts here: first inserted,then fixed by a wave solder, and finally revised.

Programming stage

Some PCBs may contain microcontrollers to reduce the number of logic gatesthat a circuit contains. Indeed, these little components are capable to surpassthe number of functions for which hundreds of logic gates would be neces-saries. To define these functions, it is needed to programme different registerswith an IDE (integrated development environment), like CodeWarrior.

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Test stage

Lastly, all PCBs must be tested following a procedure created by engineers.This allows to verify hardware and software are correctly installed, and readyto be used by customers.

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Chapter 3

Apprentice in Edison

After explaining the different stages which are necessaries to make a PCB, Iwill present the different activities in which I have participated.

3.1 Assembly stage

3.1.1 Welding task

In the preceding chapter, I have explained how it is carried out this stage:first components are assembled, then fixed in a oven. Then, a verificationtest of components is done.

In the case of verification test of SMD components, operators verify ifcomponents are correctly fixed, if there are missing components, or tin cross-ings. To re-fix a SMD component it is necessary the use of a soldering heatgun. Due to difficulty of using this heat gun, apprentices we were not allowedto use it.

In the case of verification test of trough hole components, apprenticesused to verify if there were any tin crossings, but also if these were correctlyfixed. In some occasions, I could participate in this stage that allowed me tolearn soldering.

This task consisted, basically, to melt tin crossing like shown in Figure3.1 and fix manually components. For that, a solder and some solder wire (amixture of tin/lead) are necessaries. Welding steps are schematized in Figure

18

Figure 3.1: Tin crossing

Figure 3.2: Weldering steps

3.2.

3.1.2 Attach task

Before through hole components are fixed by a wave solder, these must be at-tached manually into a PCB. Engineers who design a PCB model, also createa document called "components list" where type and location of componentsof PCB are specified. With this list apprentices are capable to place them,but usually a sample already attached was given to us. This task use to belong and repetitive as some models of PCBs could be composed of series of10 000 PCBs.

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Figure 3.3: Apprentice assembling components

3.2 Programming stage

3.2.1 Microcontroller programming task

See chapter 4.

3.2.2 Recording task

Some PCBs contains microcontrollers. These are programmed by engineersin a programming language that can be C, C++, java, VB, etc.

My task consisted in record these programmes using a recorder, that mustbe of same brand of microcontrollers (for example, freescale). Basically, PCBsneeding to be recorded have a connector in which one the recorder can beattached. The recorder is automatic, and at the end, a message of success inrecorders screen confirms recording process has finished (Figure 3.4).

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Figure 3.4: A Freescale recorder programming a PCB

3.3 Test stage

3.3.1 Test procedure

Once PCB has been programmed, a test must be done to verify hardwareand software work. At the end of PCB design, engineers create a procedurecalled Test procedure in which a list of tests must be done in order to verifydifferent sectors of the circuit correctly work.

1. If all the tests are successfully passed, a label is stuck onto the PCB,and separated to, afterwards, be packed and sent to customer.

2. If one of the tests are not passed, the PCB is separated to, later, identifythe error(s) and to be repaired.

Complexity of these tests depend on the PCB model. Some of these testswere very repetitive, whereas others, more interesting, needed of the use of aoscilloscope, since I needed to measure volts and frequency of received signals(Figure 3.5).

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Figure 3.5: A PCB passing a test procedure

3.3.2 Repairing task

Depending on the PCB model, error rate may be high. When a PCB mustbe repaired, schemas created by engineers are needed (Figure 2.9). Withthese schemas and the error generated by PCB, an engineer with enoughexperience may detect quickly failing component(s).

A lot of components and their function were unknown for me, so to repairfailing PCB, I used to take a PCB correctly working and measure values Ishould, supposedly, obtain.

Most of time, errors were generated because of components placed incor-rectly, bad welding or, simply, faulted components.

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Chapter 4

Programming a microcontroller

After some weeks of work for Edison, I asked my tutor to assign me aproject related with my speciality: ISEE (Engineering of embedded electronicsystems). My tutor proposed me some projects, and at the end, the followingwas the only one which lead to some new learnings.

4.1 Context

MC9S08SH32 is a 8-bit microcontroller with multiple peripherals like SPI(Serial Peripheral Interface), Analog-to Digital converter, or SCI (Serial Com-munication Interface).

Figure 4.1: MC9S08SH32 of freescale

23

4.1.1 Whats SCI?

A serial communications interface (SCI) is a device that enables theserial (one bit at a time) exchange of data between a microprocessor andperipherals such as printers, external drives, scanners, or mice. The termSCI is sometimes used in reference to a serial port. This is a connector foundon most personal computers, and is intended for use with serial peripheraldevices.

4.1.2 Project objective

The objective were:

1. First to configure registers to enable communication between the se-rial port of the micro and a PC. Signals sent by the micro would begenerated by some switchers and an Analog-to Digital converter of themicro. To configure these registers and to do a program (in languageC) which would interpret, for example, the touch of a switch. Thisprogramme would be charged in the micro.

2. Finally, an interface created with Visual Basic would allow to showthese informations, received by the serial port.

4.2 Programming with CodeWarrior

CodeWarrior is an integrated development environment (IDE) for the cre-ation of software that runs on a number of embedded systems.

4.2.1 Registers

CodeWarrior provides an option which creates automatically registers andfunctions necessaries to work with any peripheral of any microcontroller ofFreescales family. From a viewpoint, this option can be very useful; butkeeping in mind that one of my objectives of this project was to learn toconfigure registers, this has been more a hindrance than a help.

24

Libraries created

For each peripheral activated with this option, two documents were created:a header file (.h), with prototypes of useful functions, and a code file (.c),with the code of these functions. In this code file, a function of registersinitialization is included. Lets see an example:

void AD1_Init ( void ){

OutFlg = FALSE; / No measured value /ModeFlg = STOP; / Device i sn t running /setReg8 (ADCSC2, 0x00 ) ; / Disab le HW t r i g g e r and autocompare /setReg8 (ADCCFG, 0x00 ) ; / Set p r e s c a l e r b i t s /setReg8 (ADCSC1, 0x1F ) ; / Disab le the module /

}

The function "setReg8" takes 2 parameters: Addressee and value of theregister.

4.2.2 Programme created

The C code I have created its quite simple and it contains no more than20 lines of code. For each switch and for the A/D converter, a flag detectsa switch is pressed or the A/D value changed, an infinite boucle send thisvalue bye the serial port. Lets see an example of a switch:

i f ( (PTAD_PTAD2==0)&(flag_S1 !=1)){flag_S1=1;( void )AS1_SendChar ( 1 ) ;

} e l s e {i f (PTAD_PTAD2==1){

flag_S1=0;}

}

If PTAD_PTAD2 is pressed (Switch 1 is connected to Port A, bite 3) andthe variable flag is not activated, then the flag is activated and the character

25

Figure 4.2: Hyperterminal returns 1 when Switch 1 is pressed.

1 is sent by the serial port.

4.2.3 Hyperterminal

Hyperterminal is an application of Windows that allows communication be-tween 2 computers, or in my case, between a PC and a microcontroller. Inthis phase of the project, I used this application to display the values thatthe microcontroller sent me every time i pressed a switch or moved the A/Dconverter (Figure 4.2 and Figure 4.3).

4.3 A Visual Basic Interface

Visual Basic (VB) is a programming language developed by Microsoft fortheir operating system Windows. The BASIC language is said to be easierto read than other languages.

Unfortunately, I have never used this language and I have not had enoughtime to work in this project, so I could not finished this objective of theproject.

The first idea was to create an interface which would simulate a cockpitin which, for example, the A/D converter values, obtained by the serial port,would simulate the radio broadcasting.

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Figure 4.3: Hyperterminal returns a ASCII value every time the wheel ofA/D converter is moved

Figure 4.4: Interface with an open failure of serial port

27

Chapter 5

Conclusion

Throughout 10 weeks of internship in Edison Electronics, I have beenable to observe how this kind of company works. This internship has allowedme to see the manufacturing process of PCBs.

However, I do not think having reached the goals I had set for myselfat the beginning of this internship ; moreover I acquired only partially theknowledge that I think I could have obtained from this company.

Edison Electronics is a family business with 20-year experience, stillsome problems of structuring and organisation were evident. For instance,discussions about lost or poorly ordered material were frequent. I dont findthat the company employed my abilities, as an engineer student, but only asan labourer.

For several reasons, I have not been tutored adequately by the personwho was in charge of me.

From a global point of view, the tasks I did in this company had noeducational interest.

Fortunately, I met wonderful people who gave me the motivation to con-tinue, and also a lot of useful advice.

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Bibliography

All information shown in Chapter 2, is extracted from the following websites:

Information about SMD and THT : http://goo.gl/DG5G5Z Information about design stage : http://goo.gl/eXYJUa Information about different layers of a PCB : http://goo.gl/qnoggN Information about production stages : http://goo.gl/21DbDi

29

Rsum

Edison Electronics S.L est une organisation fonde en1995 Badalona (Barcelona) et ddie la conception et lassemblagede cartes lectroniques. Son travail stend lchelle nationale, laplupart du temps avec les clients dans la communaut autonomede Catalogne. Les cartes lectroniques, ou Printed Circuit Boards(PCBs) en anglais, sont prsentes aujourdhui en tout systmelectronique, et comprendre les tapes de fabrication et leur util-isation est de vital importance pour tout tudiant spcialis enl?lectronique embarqu.

Abstract

Edison Electronics S.L is a company set up on 1995 inBadalona (Barcelona), and dedicated to the design and assemblyof electronic cards. His work extends nationwide, mostly withclients in the autonomous community of Catalonia. Printed Cir-cuit Boards (PCBs) are present today in any electronic system,and understand the stages of manufacture and their use is vitalto any student specializing in embedded electronics.

IntroductionEDISON Electronics...... a family business.... a company focused on SMD.What is SMD?PCB, the base of an electronic circuitDesign and assembly stages

Apprentice in EdisonAssembly stageWelding taskAttach task

Programming stageMicrocontroller programming taskRecording task

Test stageTest procedureRepairing task

Programming a microcontrollerContextWhat's SCI?Project objective

Programming with CodeWarriorRegistersProgramme createdHyperterminal

A Visual Basic Interface

Conclusion