I2C HMC6352 compass heading (sparkfun breakout) by BARRAGAN (http://barraganstudio.com)

Demonstrates use of the Wire library reading data from the HMC6352 compass heading On Wiring v1 boards the SCL and SDA pins are: 0 and 1 On Wiring S board the SCL and SDA pins are: 8 and 9

#include <Wire.h> 

int compassAddress = 0x42 >> 1; // From datasheet compass address is 0x42
// shift the address 1 bit right, the Wire library only needs the 7
// most significant bits for the address
int reading = 0; 

void setup() 
{ 
  Wire.begin();       // join i2c bus (address optional for master) 
  Serial.begin(9600); // start serial communication at 9600bps 
  pinMode(WLED, OUTPUT);
  digitalWrite(WLED, HIGH);
} 

void loop() 
{ 
  // step 1: instruct sensor to read echoes 
  Wire.beginTransmission(compassAddress);  // transmit to device
  // the address specified in the datasheet is 66 (0x42) 
  // but i2c adressing uses the high 7 bits so it's 33 
  Wire.write('A');        // command sensor to measure angle  
  Wire.endTransmission(); // stop transmitting 

  // step 2: wait for readings to happen 
  delay(10); // datasheet suggests at least 6000 microseconds 

  // step 3: request reading from sensor 
  Wire.requestFrom(compassAddress, 2); // request 2 bytes from slave device #33 

  // step 4: receive reading from sensor 
  if (2 <= Wire.available()) // if two bytes were received 
  { 
    reading = Wire.read();  // receive high byte (overwrites previous reading) 
    reading = reading << 8; // shift high byte to be high 8 bits 
    reading += Wire.read(); // receive low byte as lower 8 bits 
    reading /= 10;
    Serial.println(reading); // print the reading
  } 

  delay(500); // wait for half a second
}