Code for Compass Module test

DigitalCompass.ino

//This reads the heading from HMC6352, spit it out via serial and lights up 1-2 lights to show North
//HMC6352 compass is hooked up this way: SDA is on analog input pin 4, and SCL is on analog pin 5

#include <Wire.h>
int HMC6352SlaveAddress = 0x42;
int HMC6352ReadAddress = 0x41; //"A" in hex, A command is: 

int headingValue;

int EPin = 13;//east
int SPin = 12;//south
int WPin = 9;//west
int NPin = 8;//north

void setup(){
  // "The Wire library uses 7 bit addresses throughout. 
  //If you have a datasheet or sample code that uses 8 bit address, 
  //you'll want to drop the low bit (i.e. shift the value one bit to the right), 
  //yielding an address between 0 and 127."
  HMC6352SlaveAddress = HMC6352SlaveAddress >> 1; // I know 0x42 is less than 127, but this is still required

  pinMode(WPin, OUTPUT);  
  pinMode(NPin, OUTPUT);  
  pinMode(EPin, OUTPUT);  
  pinMode(SPin, OUTPUT);  
  Serial.begin(9600);
  Wire.begin();
}

void loop(){
  //"Get Data. Compensate and Calculate New Heading"
  Wire.beginTransmission(HMC6352SlaveAddress);
  Wire.write(HMC6352ReadAddress);              // The "Get Data" command
  Wire.endTransmission();

  //time delays required by HMC6352 upon receipt of the command
  //Get Data. Compensate and Calculate New Heading : 6ms
  delay(6);

  Wire.requestFrom(HMC6352SlaveAddress, 2); //get the two data bytes, MSB and LSB

  //"The heading output data will be the value in tenths of degrees
  //from zero to 3599 and provided in binary format over the two bytes."
  byte MSB = Wire.read();
  byte LSB = Wire.read();

  float headingSum = (MSB << 8) + LSB; //(MSB / LSB sum)
  float headingInt = headingSum / 10; 

  Serial.print(headingInt);
  Serial.println(" degrees");
  
  //North
  if (headingInt > 330 || headingInt < 30 ){
    digitalWrite(NPin, HIGH); 
    digitalWrite(EPin, LOW);
    digitalWrite(SPin, LOW);
    digitalWrite(WPin, LOW);
  } 
  //NorthEast
  if (headingInt > 30 && headingInt < 60 ){
    digitalWrite(NPin, HIGH);
    digitalWrite(EPin, HIGH); 
    digitalWrite(SPin, LOW);
    digitalWrite(WPin, LOW);
  }
  //East
  if (headingInt > 60 && headingInt < 120 ){
    digitalWrite(EPin, HIGH);
    digitalWrite(SPin, LOW);
    digitalWrite(WPin, LOW);
    digitalWrite(NPin, LOW);
  }
  
  //SouthEast
  if (headingInt > 120 && headingInt < 150 ){
    digitalWrite(EPin, HIGH);
    digitalWrite(SPin, HIGH);
    digitalWrite(NPin, LOW);
    digitalWrite(WPin, LOW);
  } 
  //South
  if (headingInt > 150 && headingInt < 210 ){
    digitalWrite(SPin, HIGH);
    digitalWrite(NPin, LOW);
    digitalWrite(WPin, LOW);
    digitalWrite(EPin, LOW);
  }
  //SouthWest
  if (headingInt > 210 && headingInt < 240 ){
    digitalWrite(SPin, HIGH);
    digitalWrite(WPin, HIGH);
    digitalWrite(EPin, LOW);
    digitalWrite(NPin, LOW);
  }
  //West
  if (headingInt > 240 && headingInt < 300 ){
    digitalWrite(WPin, HIGH);
    digitalWrite(SPin, LOW);
    digitalWrite(EPin, LOW);
    digitalWrite(NPin, LOW);
  }
  //NorthhWest
  if (headingInt > 300 && headingInt < 330 ){
    digitalWrite(NPin, HIGH);
    digitalWrite(WPin, HIGH);
    digitalWrite(SPin, LOW);
    digitalWrite(EPin, LOW);
  }


  delay(100);
}