Compass

Components

• Compass Module CMPS03 http://www.robot-electronics.co.uk/htm/cmps3tech.htm
• DC Boarduino http://learn.adafruit.com/boarduino-kits/dc-parts-list
• FTDI Friend http://www.adafruit.com/products/284

Other potential components

• SCF5740 Siemens (OSRAM) 4 digit display http://catalog.osram-os.com/media/_en/Graphics/00034126_0.pdf
• 0.96" OLED Display https://www.adafruit.com/products/684
• FTDI/USB http://www.parallax.com/catalog/integrated-circuits/ftdi

Code

The following will give a compass heading via serial monitor

/*
CMPS03 with arduino I2C example

This will display a value of 0 - 359 for a full rotation of the compass.

The SDA line is on analog pin 4 of the arduino and is connected to pin 3 of the CMPS03.
The SCL line is on analog pin 5 of the arduino and is conected to pin 2 of the CMPS03.
Both SDA and SCL are also connected to the +5v via a couple of 1k8 resistors.
A switch to callibrate the CMPS03 can be connected between pin 6 of the CMPS03 and the ground.
*/

#include <Wire.h>

#define ADDRESS 0x60 //defines address of compass

void setup(){
  Wire.begin(); //conects I2C
  Serial.begin(9600);
}

void loop(){
  byte highByte;
  byte lowByte;
  
   Wire.beginTransmission(ADDRESS);      //starts communication with cmps03
   Wire.write(2);                         //Sends the register we wish to read
   Wire.endTransmission();

   Wire.requestFrom(ADDRESS, 2);        //requests high byte
   while(Wire.available() < 2);         //while there is a byte to receive
   highByte = Wire.read();           //reads the byte as an integer
   lowByte = Wire.read();
   int bearing = ((highByte<<8)+lowByte)/10; 
   
   Serial.println(bearing);
   delay(100);
}