Tutorial: Introduction to the Arduino

--D. Thiebaut 15:18, 20 April 2011 (EDT)

Before You Start Playing...

Video Introduction

Excellent introduction to the Arduino, its team, and some of the projects.

Good Reference Pages

The Arduino Language Reference
The Getting Started guide
The CSC231 Arduino project page (Fall 2008)

Good Tutorials on the Web

Arduino Tutorial at UCLA (currently unavailable)

Notes for Mac Users

You may have to install special drivers for your Mac to see the Arduino through the USB Port. Look here for more info: http://www.ftdichip.com/Drivers/VCP.htm

Important Concepts to Understand before Starting...

Action	Laptop	Arduino
Programs are written on the laptop	X
Programs are compiled on the laptop	X
Programs are downloaded to the Arduino	src	dest
Programs run on the Arduino		X
Programs output text information via the USB cable, and this information is captured by the IDE which shows it in the Serial Monitor.	display	print
The Arduino inputs character information that the User types in the Serial Monitor. This information is sent via the USB cable to the Arduino.	char sent in Monitor	get 1 char from USB

Circuits and Systems

This is just a very rough introduction to the Arduino circuits, and useful only as a support for an in-class presentation of the Arduino. Please refer to http://arduino.cc/en/Tutorial/Foundations for in-depth coverage of all these concepts.

Digital I/Os

Main reference: http://arduino.cc/en/Tutorial/DigitalPins
14 pins
Each can be input or output
5-Volt range
40 mA max
Internal pull-up resistor (disconnected by default)
Special pins
- Pins 0 & 1: Used to exchange data with USB
- Pins 2 & 3: can be used as interrupt pins (i.e. can trigger events)
- Pins 3, 5, 6, 9, 10, and 11: 8-bit Pulse-Width Modulation.
- Pin 13: on-board LED.

Analog Input

6 Analog inputs
each 10-bit resolution
range = 0 - 5 Volts.
- 0V --> 0
- 5V --> 1023
Important Note: Analog input pins can also be used as digital output pins. See http://www.arduino.cc/en/Tutorial/AnalogInputPins for more information.

Simulated Analog Output (PWM)

Digital Pins 3, 5, 6, 9, 10, and 11 can be used in 8-bit Pulse-Width Modulation.
Frequency = 500Hz, ==> Period = 2 ms
8-bit value: range = 0 --> 255
- 0 --> 0% duty cycle: constant low level output
- 127 --> 50% duty cycle: 50% of the time, the signal is low, 50% high.
- 255 --> 100% duty cycle: constant high level output
taken from http://www.arduino.cc/en/Tutorial/PWM

An Introduction to C in the Arduino Context

Comments

// this is a comment
/* and so is this */
/* and
    this 
    as 
    well */

Setup() and Loop()

Text Input/Output

Output strings from the Arduino to Laptop

Done with the Serial library
Use Serial.begin() to set the baud rate (# of bits per second)
Then output strings with Serial.println( ... ) or Serial.print( ... )

void setup() {                
 Serial.begin( 38400 );
 Serial.println( "Hello there!" );
}

void loop() {
 delay(1000);              // wait for a second
 Serial.println( "hello again!" );
}

Output numbers

Taken from http://arduino.cc/en/Serial/Print
- Serial.print(78) gives "78"
- Serial.print(1.23456) gives "1.23"
- Serial.print(byte(78)) gives "N" (whose ASCII value is 78)
- Serial.print('N') gives "N"
- Serial.print("Hello world.") gives "Hello world."

An optional second parameter specifies the base (format) to use; permitted values are BYTE, BIN (binary, or base 2), OCT (octal, or base 8), DEC (decimal, or base 10), HEX (hexadecimal, or base 16). For floating point numbers, this parameter specifies the number of decimal places to use. For example:

- Serial.print(78, BYTE) gives "N"
- Serial.print(78, BIN) gives "1001110"
- Serial.print(78, OCT) gives "116"
- Serial.print(78, DEC) gives "78"
- Serial.print(78, HEX) gives "4E"
- Serial.println(1.23456, 0) gives "1"
- Serial.println(1.23456, 2) gives "1.23"
- Serial.println(1.23456, 4) gives "1.2346"

Inputting characters

Use Serial.read() and Serial.available(), as illustrated below

void setup() {                
  Serial.begin( 38400 );
  Serial.println( "Enter one characterA in the console and send it: " );
}

void loop() {
  int charByte;
  
  if ( Serial.available() > 0 ) {
    charByte = Serial.read();
    Serial.print( charByte, DEC );
    Serial.print( " is " );
    Serial.print( charByte, HEX );
    Serial.print( " in hex.\n\n\n" );
    Serial.println( "Enter another character in the console and send it: " );
  }
}

Statements

statement;
statement;
statement;
// comment
statement;
compound-statement {
       statement;
       statement;
}

Control Statements

IF

if ( condition equal to 0 or different from 0 ) {
      // Action A
}
else {
      // Action B
}

FOR

same syntax and structure as in Java.
you can declare the variable in the loop.
the variable is undefined outside the loop.

for ( int i = 0; i < 100; i++ ) {
      statement;
      statement;
}

SWITCH

works with countable variables (not floats).

switch (var) {
   case 1:
     //do something when var equals 1
     break;
   case 2:
     //do something when var equals 2
     break;
   default: 
     // if nothing else matches, do the default
     // default is optional
 }

WHILE

while (expression evaluating to 0 or something different from 0 ) {
    statement;
    statement;
    statement;
}

BREAK/CONTINUE

break: break out of the most inner loop it is located in.
continue: skips the remainder of the current loop and returns to the closest for or while statement.

Variables and Data Types

void
boolean
char
unsigned char
byte
int
unsigned int
word
long
unsigned long
float
double
string (array of chars)
String (object) (see http://arduino.cc/en/Reference/StringObject)
array (see http://arduino.cc/en/Reference/Array)

Examples

int LEDpin = 5;       // LED on pin 5
int switchPin = 13;   // momentary switch on 13, other side connected to ground
boolean running = false;

char myChar = 'A';
char myChar = 65;      // both are equivalent

byte b = B10010;  // "B" is the binary formatter (B10010 = 18 decimal) 

float myfloat;
float sensorCalbrate = 1.117;

char Str1[15];
char Str2[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o'};
char Str3[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o', '\0'}; 
char Str4[ ] = "arduino";
char Str5[8] = "arduino";
char Str6[15] = "arduino";

String stringOne = "Hello String";                     // using a constant String 
String stringOne =  String('a');                       // converting a constant char into a String
String stringTwo =  String("This is a string");        // converting a constant string into a String object
String stringOne =  String(stringTwo + " with more");  // concatenating two strings
String stringOne =  String(13);                        // using a constant integer
String stringOne =  String(analogRead(0), DEC);        // using an int and a base
String stringOne =  String(45, HEX);                   // using an int and a base (hexadecimal)
String stringOne =  String(255, BIN);                  // using an int and a base (binary)
String stringOne =  String(millis(), DEC);             // using a long and a base

int myInts[6];
int myPins[] = {2, 4, 8, 3, 6};
int mySensVals[6] = {2, 4, -8, 3, 2};
char message[6] = "hello";


	Exercise Create a sketch based on the Blink sketch (in File/Examples/1. Basics) that outputs alternatively "hello" one second, then your name the next second, in an endless loop.


	Exercise Create a sketch that outputs the word Green one second, then outputs Yellow the next, then outputs Red the next, returning to Green the second after that. See example below.


	Exercise Same as previous one, but make the delay between outputs a quarter of a second.

Functions

Taken from http://arduino.cc/en/Reference/FunctionDeclaration

Static variables

 int process( int offset ) {
      static int current=0;
      
      current += offset;
      ...
 }

Digital Output

The Basics

The Arduino sports 14 output pins: Digital 0 to 13
Steps:
- in setup(), use pinMode() to identify what pin you will use, and set the direction of data transfer as OUTPUT
- in loop(), use digitalWrite( ) to output HIGH or LOW to that pin.

Example

int ledPin = 13;                 // LED connected to digital pin 13

void setup()
{
  pinMode(ledPin, OUTPUT);      // sets the digital pin as output
}

void loop()
{
  digitalWrite(ledPin, HIGH);   // sets the LED on
  delay(1000);                  // waits for a second
  digitalWrite(ledPin, LOW);    // sets the LED off
  delay(1000);                  // waits for a second
}

Exercises


	Exercise Follow the steps from http://arduino.cc/en/Tutorial/Blink and create a similar system. Instead of soldering the LED to the resistor, use the breadboard or aligator clips.


	Exercise Use the same approach and create a sketch that will controls 3 LEDs (which will represent a Green light, Yellow light, and Red light), and will alternate between all three in a cycle.

Digital Input

The approach is similar to the one take for output bits.


void setup() {
  Serial.begin(9600);
  pinMode(2, INPUT);
}

void loop() {
  int sensorValue = digitalRead(2);
  Serial.println(sensorValue, DEC);
}

Exercises


	Exercise Follow the steps from http://arduino.cc/en/Tutorial/Button, and control the on-board LED with the external switch.


	Exercise Replace the on-board LED by an external LED wired in a way similiar to the previous exercise.

Analog Input

Use the analogRead() function to read an analog value from a given pin:

void loop() {
  int sensorValue = analogRead(A0);  // Note: A0 is predefined
  Serial.println(sensorValue, DEC);   // display value on Monitor
}

Exercise


	Exercise Follow the steps presented in http://arduino.cc/en/Tutorial/AnalogReadSerial and build a simple meter that measures the rotation of a potentiometer.