Arduino introduction

Installation

Windows

Arduino and AVR

Serial communication from Arduino to computer

void setup()
{
  //sets the baud rate and initializes serial communication
  Serial.begin(9600);  
}

void loop()
{
  //send message
  Serial.println("Hello world!");
  //wait for one second
  delay(1000);
}

Linux

Windows

Speaker beep example

void setup() {                
}

/* 
   square wave tone on pin# pin
   freq in Hz and duration in ms
 */
void play_tone(int pin, int freq, int duration) {
  int i = 0;
  int sleep = 1000 / (2*freq);
  int periods = duration / (2 * sleep);
  pinMode(pin, OUTPUT);
  for (i = 0 ; i < periods; i++) {
    digitalWrite(pin, 1);
    delay(sleep);
    digitalWrite(pin, 0);
    delay(sleep);
  }
}

void loop() {
  play_tone(13, 220, 1000);
  delay(1000);  
}

Switch example

/*
Connect a switch between GND and pin 7.
Will transmit "Closed" / "Open" whenever the switch closes or
opens.
*/

int switch_state = HIGH;

void setup() {
  Serial.begin(9600);
  pinMode(7, INPUT);
  // activate pull-up resistor on pin 7
  digitalWrite(7, HIGH);
}

void loop() {
  int state = digitalRead(7);
  if (state != switch_state) {
    switch_state = state;
    if (switch_state == HIGH)
      Serial.println("Open");
    else
      Serial.println("Closed");
  }
  delay(1);
}

Blinkenlights example

/* 
  Blinkenlights program, which listens for commands
  to turn LEDs on or off.

   Serial data :
   A - turn on LED 0 (at pin 2)
   B - turn on LED 1 (at pin 3)
   ...
   a - turn off LED 0
   b - turn off LED 1
   ...
*/   

// number of LEDs
int n_leds = 12;

// skip pins 0 and 1. They are needed for serial rx and tx
int first_led = 2; 

// on / off commands 
int first_led_on = 'A';
int first_led_off = 'a';

// serial data
int data;

void setup() {
  int i;
  for (i = 0; i < n_leds; i++) {
    pinMode(first_led + i, OUTPUT);
    digitalWrite(first_led + i, LOW); // start with everything off
  }
  Serial.begin(9600);
}


void loop() {
  //look for incoming data
  if (Serial.available() > 0) {
    data = Serial.read();
    if (data >= first_led_on && data < first_led_on + n_leds) {
      //turn on
      digitalWrite(data - first_led_on + first_led, HIGH);
    }
    if (data >= first_led_off && data < first_led_off + n_leds) {
      //turn off
      digitalWrite(data - first_led_off + first_led, LOW);
    }    
  }  
  delay(1);
}

#!/usr/bin/python
import sys
import serial
import time
import os

device = "/dev/ttyUSB0"
if (len(sys.argv) > 1) :
  device = sys.argv[1]

ser = serial.Serial(device)
ser.baudrate = 9600

blink_data = []
# Add more entries to taste
# Format: (file to monitor, On command, Off command)
blink_data.append(("/var/log/httpd/access_log", 'L', 'l'))

mod_time = []
for entry in blink_data :
  mod_time.append(time.localtime(os.path.getmtime(entry[0])))

while (True):
  index = 0
  for entry in blink_data :
    t = time.localtime(os.path.getmtime(entry[0]))
    if (mod_time[index]) != t :
      mod_time[index] = t
      ser.write(entry[1])  # Send ON
    else :
      ser.write(entry[2])  # Send OFF
    index = index + 1
  time.sleep(1)

Further examples