Subversion Repositories group.electronics

#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(13, OUTPUT);

  digitalWrite(13, 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

}