Arduino GY-273 HMC5883L Magnetometer Compass Tutorial

Find Your Heading with an Arduino

GY-273 Arduino TutorialBased on the Honeywell HMC5883L,  the GY-273 sensor module allows you add an electronic compass to your projects.  While coding for the device can be a bit of a chore,  there available libraries that make putting it to practical us a snap.

The device communicates with your Arduino via I2c.

This tutorial will show you how to connect the sensor and run sample sketch.  It will also point you to  a fantastic Adafruit library that will make using the device easy.

Getting a GY-273

eBay     Amazon     AliExpress

GY-273 Sensor Module Pin-outs

The device has five pins.  In most applications  (and this tutorial),  you will only be concerned with four of them.

GY-273 Magnetometer Pin OutsFunctional Description

This is a pretty complicated device, that by itself could take pages to describe.   This tutorial simply highlights the basics.

The Honeywell HMC5883L sensor used in the module is sensitive to the earths magnetic fields in three axes.  These axes are labeled as X, Y, and Z.     An output is provided for each of these axes that describes the position of these axes relative to the earth’s magnetic field.

As illustrated, twisting or turning the device  will provide the corresponding outputs.

GY-273 Magnetometer Rotation vs OutputGY-273 Arduino Basic Output Tutorial

In this tutorial, you will connect the GY-273, load a basic sketch and see an output to your serial monitor.  The purpose of this tutorial is to verify that you can read and output and to

Connect the Arduino to the GY-273

Just four connections are required.  Refer to the picture below.

GY-273 Magnetometer Tutorial hook up

Copy, Paste and Upload the GY-273 Example Sketch


#include <Wire.h> //I2C Arduino Library

#define addr 0x1E //I2C Address for The HMC5883

void setup(){
  Wire.beginTransmission(addr); //start talking
  Wire.write(0x02); // Set the Register
  Wire.write(0x00); // Tell the HMC5883 to Continuously Measure

void loop(){
  int x,y,z; //triple axis data

  //Tell the HMC what regist to begin writing data into
  Wire.write(0x03); //start with register 3.
 //Read the data.. 2 bytes for each axis.. 6 total bytes
  Wire.requestFrom(addr, 6);
    x =<<8; //MSB  x 
    x |=; //LSB  x
    z =<<8; //MSB  z
    z |=; //LSB z
    y =<<8; //MSB y
    y |=; //LSB y
  // Show Values
  Serial.print("X Value: ");
  Serial.print("Y Value: ");
  Serial.print("Z Value: ");

Open the Serial Monitor and Verify Your Output.

Your output should look something like this.  Once you’ve established that you have an output,  try turning your device along it’s various axes and view the results.

GY-273 Arduino Tutorial Output

Run the Adafruit Example

You won’t need to change any of your connections.

Get the Libraries

If you don’t already know this,  Adafruit is an awesome contributor to the Arduino community.  In fact, if you’re a buyer of Arduino devices,  I highly recommend you throw a few dollars their way on occasion.  They’ve earned it.

In the case of the HMC5883L,  they’ve put together a couple libraries that will really get you going in the right direction.   If you’re not familiar with using libraries for other devices,   I suggest reading the instructions on the Arduino website.

Like I alluded to, you will need two libraries…

The first is Adafruit’s Unified Sensor Library..  Found HERE

The second is Adafruit’s HMC5883L Library… Found HERE

Run Adafruit’s HMC5883L Example

Navigate to the Examples directory under your Arduino IDE file menu.  You’ll find the HMC5883 example there.  Open it, upload it and open your serial monitor.

When the plane defined by the X and Y axes is parallel to the ground,  you will get an output that indicates a compass heading.

GY-273 Adafruit Output Example