How to use Arduino

www.arduino.cc

By: Andrew Hoffmaster

Computers

• Computers talk in ones and zeros binary• We need language to convert English to Binary • The converter commonly used is C

What is a microcontroller

• Portable DAQ with on board processing power

• Used everywhere: power strips, calculators • Versatile with wide range of applications

Advantages and Disadvantages of Microcontrollers

• Advantages– Small– Portable– No Computer required – Programmable logic– Vast range of

applications– Cheap

• Disadvantages– Limited by ADC– Limited processing

power– No data storage

Arduino

• Italian made by ATMEGA • Development boards allow for easy use and

adaptability• Open source programming language • “Plug in and use” usability

Development boards

http://arduino.cc/en/Main/Hardware

Digital I/O

Analog inputsPower outputs

USB input

9V external power source

Initial steps

• Go to www.arduino.cc• Download the latest version for you computer

http://arduino.cc/en/Main/Software

• You may need to download drivers for the board you are using ( UNO or MEGA) but they come with the download they are just difficult to locate

Basics of Coding Arduino

• Arduino’s programming language is a version of C, most C commands work in the sketch editor

• Four basic components of Ardunio speak – Initialization– Setup – Loop– User defined functions

Initialization

• Include any extra libraries you are using• All variables need to be initialized • A=4; will not work int a= 4; will • Define variables you will assign later – Int a,b,c;

• Remember data structures – Int, double, float, char, string ….

Here you can see the library Math.h is included in the code this will allow the use to use math functions like cos sin tan …

ax, ay, az, gx, gy, gz are defined to specific values

These values will be assigned later but need to be initialized

Setup

• Initialization for the arduino board • Usually begin Serial communication • Usually assign digital pins to input or output

Void means setup will not output anything

pinMode defines the state of digital pins to OUPUT or INPUT.

Serial.begin(9600) opens serial communication at 9600 baud

Loop

• Loop is the main portion of the arduino code• Loop is what the microcontroller will do

forever • This is very much like a never ending for loop

User defined functions

• These functions can be called in the loop and are usually responses to conditions that are met in the loop.

• These functions must be defined with data structure and output type

User defined functions

• Here is a basic map function for floats • The user inputs a float x and the function

maps the number from an old data range to a new data range. float mapFloat(float x, float in_min, float in_max, float out_min, float out_max){return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;}

• float mapFloat(float x, float in_min, float in_max, float out_min, float out_max)• {• return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;• }

Defines output type as float and names function mapFloat

Inputs and their data types in this case they are all floats

Return is what the function output which is defined above as a float

The curly brackets { and } define what is inside the function these separate blocks of code and are very important

You can indent the inside of the code it is up to you and what fits your style

Analog v Digital

• Analog is a continuous signal (Voltage) in which the variable of the signal is a representation of some other time varying quantity. Hence analogous

• Digital is a physical signal that represents a sequence of discrete values. On and off like binary 1 and 0

ADC and DAC

• Analog Digital Converter- Computer cannot read Analog values only digital ( 5V or Gnd)

• Measured in bits 2^n example 10 bit = 2^10 = 1024

• Digital Analog Converter convert digitals signal to analog signal, Voltage

Analog to Digital

• Computers read Digital signals • Some sensors output analog signals (Voltage) • We read this voltage as a Bit – On a 5V analog pin 2.5 V is half of the number of

available bits• Precision depends on the number of Bits in

our ADC – With a 10 bit ADC bit= (Voltage/Vref )* num bits

ADC

Example

• A 2.5 V signal is applied to a 5Vref analog pin with a 10 bit ADC what bit is displayed?

– Answer: (2.5 / 5) * 1024 = 512

Analog Data

• The Arduino has analog ports labeled Analog in

• These are 10 bit data inputs that range from 0 to 5V although this can be changed

• Information is sent to the computer through USB line using the Serial library.

• Information can also be sent via the serial lines in the arduino

Simple Serial Communication

• Two wire communication– Tx to write data to an object – Rx to receive data– Labeled as digital ports 0 (Rx) and 1(Tx) on arduino

• For USB communication select the correct device (tools – board) and com port

• Open serial monitor to view incoming serial data (top right icon)

Serial Library

• Serial.begin(baudrate) – Opens Serial Port at baudrate

• Serial.avilable()– Returns the number of bytes available to read

• Serial.read()– Returns the first byte of incoming serial data available (or -1 if no data

is available)

• Serial.print(data,format)– Prints data to the serial port as readable ASCII text

• Serial.println(data,format)• Prints data to the serial port as readable ASCII text then ends the line

• http://arduino.cc/en/Reference/Serial

Analog Library

• analogReference(type)– Default is 5 V signal External is voltage applied to

VREF• analogRead(port)– Reads data coming into analog port, 1024 values

or 10 bit data• http://arduino.cc/en/Reference/AnalogRefere

nce

Digital Library

• pinMode(pin,mode)– Set as INPUT or OUTPUT

• digitalWrite(pin,state)– Write to HIGH 5v or LOW 0v or ground

• digitalRead(pin)– Returns high or low (1 or 0)

Control Structrues

If(variable comparison operator condition){

do something}

for(initialization; condition; increment) {

do something}

Computer checks to see if the condition is met for the variable and responds accordingly

Computer does something for a certain number of time for example read 500 lines of data very quickly

Comparison Operators

• == equal to• != not equal to• < less than• > greater than • <= less than or equal to • >= greater than or equal to

Boolean Operators

• && and• || or• ! not

Compound Operators

• ++ increment • -- decrement• += compound addition • -= compound subtraction • *= compound multiplication • /= compound division

What are compound operators?

• X+=4 is the same as X=X+4

• X*=2 is the same as X=X*2

• X=1 X++ means X=1 and during the next loop X=X+1 or X+=1

Data Structures

• Int • Double • Float • Char • String• Hex

How to start codingHardware setup

• Use a USB A to B cable to plug you computer into the arduino

• Plug the desired signals into the ports you choose (Digital to digital ports)

• Make sure to plug in LED’s the correct way

How to start codingSoftware setup

Open the Arduino main window shown on the left

Download is available at www.arduino.cc

Arduino environment

http://www.ladyada.net/learn/arduino/lesson1.html

Uploading code

Compile Upload Serial Monitor

Under tools make sure Board is the board you and using and Serial port is checked and is the correct port

First Code

Blink explained

• There are no variables assigned in this code so the first part is the setup

• We are not using any Serial communication so we only need to initialize the pinMode

• Writing the pin state to High will turn the LED on the board on, writing it to Low will turn the LED off

• The delay is in ms which causes the blink

Potentiometer setup

• Attach the outer wires of the potentiometer to the +5 and ground outputs on the arduino

• Insert the center wire on the potentiometer to the Analog input 0 (A0)

Advanced Projects

• Each project using arduino will be a combination of complex circuits and programming

• The two basic places of failure are faulty wiring or faulty coding

Wiring tips

• Always look at data sheet or schematic • Ground all circuits • Do not confuse analog and digital i/o• Digital outputs can only output 0 or 5 V and

very low current <500ma • Use digital out with relays for high current

applications

Coding tips

• Always follow basic structure initialize, setup, loop, user functions

• If you do not know how to do something use the internet

• Arduino forum is very helpful • Keep trying