Dear Sir

I bought the Digital Compass module HMC6352 last month.
Today I connected it with the Arduino.
I copied the follwing code from some guy’s blog.
It works but the result is starnge.
When the arrow with the character ‘N’ on the module points to the Sourth, the value is close to zero.

I would like to know the measured value of the Digital Compass module HMC6352 is the relative value or the absolute one.
Thanks very much.

#include <Wire.h>
int HMC6352Address = 0x42;
// This is calculated in the setup() function
int slaveAddress;
int ledPin = 13;
boolean ledState = false;
byte headingData[2];
int i, headingValue;
void setup()
// Shift the device’s documented slave address (0x42) 1 bit right
// This compensates for how the TWI library only wants the
// 7 most significant bits (with the high bit padded with 0)
slaveAddress = HMC6352Address >> 1; // This results in 0x21 as the address to pass to TWI
pinMode(ledPin, OUTPUT); // Set the LED pin as output
void loop()
// Flash the LED on pin 13 just to show that something is happening
// Also serves as an indication that we’re not “stuck” waiting for TWI data
ledState = !ledState;
if (ledState) {
// Send a “A” command to the HMC6352
// This requests the current heading data
Wire.send(“A”); // The “Get Data” command
delay(10); // The HMC6352 needs at least a 70us (microsecond) delay
// after this command. Using 10ms just makes it safe
// Read the 2 heading bytes, MSB first
// The resulting 16bit word is the compass heading in 10th’s of a degree
// For example: a heading of 1345 would be 134.5 degrees
Wire.requestFrom(slaveAddress, 2); // Request the 2 byte heading (MSB comes first)
i = 0;
while(Wire.available() && i < 2)
headingData[i] = Wire.receive();
headingValue = headingData[0]*256 + headingData[1]; // Put the MSB and LSB together
Serial.print(“Current heading: “);
Serial.print(int (headingValue / 10)); // The whole number part of the heading
Serial.print(int (headingValue % 10)); // The fractional part of the heading
Serial.println(" degrees");

It is absolute value. :slight_smile: