HMC5883L vs QMC5883L: 3-Axis Magnetometer Comparison for Arduino

If you have ever ordered a GY-273 magnetometer module expecting to get an HMC5883L and ended up with code that does not work, you have stumbled into one of the most confusing situations in the maker electronics world. The HMC5883L from Honeywell and the QMC5883L from QST Corporation look identical on the breakout board, have almost identical names, but are fundamentally different ICs with different I2C addresses, different register maps, and different initialisation sequences. This comprehensive guide explains exactly how to identify which chip you have, shows you how to wire and code both correctly, and helps you build a tilt-compensated digital compass that works reliably with Arduino.

1. How to Identify HMC5883L vs QMC5883L

The GY-273 PCB silkscreen often says “HMC5883L” even when the actual chip is a QMC5883L. The easiest way to check is through software:

#include <Wire.h>

void setup() {
  Wire.begin();
  Serial.begin(115200);
  // HMC5883L is at 0x1E; QMC5883L is at 0x0D
  for (byte addr : {0x0D, 0x1E}) {
    Wire.beginTransmission(addr);
    byte err = Wire.endTransmission();
    if (err == 0) {
      Serial.print("Device found at 0x");
      Serial.println(addr, HEX);
      if (addr == 0x1E) Serial.println("→ This is an HMC5883L");
      if (addr == 0x0D) Serial.println("→ This is a QMC5883L");
    }
  }
}
void loop() {}

You can also check physically: if you have a magnifier or USB microscope, look at the IC markings. HMC5883L usually has “5883” or “H5883” visible; QMC5883L chips often show “QMC” or “Q5883”.

A third method: read the identification register. For HMC5883L, register 0x0A returns 0x48 (‘H’). The QMC5883L has a Chip ID register at 0x0D that returns 0xFF on most samples.

2. Specifications Comparison

Key takeaway: The QMC5883L is not an HMC5883L clone in any functional sense — it has a different address, different registers, and a higher data rate. The HMC5883L has been discontinued by Honeywell, so the vast majority of GY-273 modules being sold today in India contain the QMC5883L.

3. HMC5883L: Wiring and Initialisation

The GY-273 module includes a 3.3 V LDO and I2C pull-ups, making it safe to connect directly to 5 V Arduino boards.

GY-273 (HMC5883L) → Arduino Uno
VCC  → 5 V (module has onboard 3.3 V LDO)
GND  → GND
SCL  → A5
SDA  → A4
DRDY → D2 (optional, for interrupt-driven reads)

The I2C address is fixed at 0x1E — there is no address selection pin. This means you can only have one HMC5883L on the same I2C bus (unless you use an I2C multiplexer like the TCA9548A).

4. QMC5883L: Wiring and Initialisation

Wiring is identical to the HMC5883L — same GY-273 board layout, same pins. The only difference is the I2C address in your code:

GY-273 (QMC5883L) → Arduino Uno
VCC  → 5 V
GND  → GND
SCL  → A5
SDA  → A4
// I2C address in code: 0x0D (NOT 0x1E!)

The QMC5883L also has a SET/RESET pin (sometimes labelled SETP) that connects to a capacitor on the module for demagnetisation. The GY-273 module handles this with a capacitor already on the PCB — do not connect any external circuitry to this pin.

5. Arduino Code for HMC5883L

Install the QMC5883LCompass library (ironically, it supports both chips) or use the Adafruit HMC5883 Unified library.

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_HMC5883_U.h>

Adafruit_HMC5883_Unified mag(12345);

void setup() {
  Serial.begin(115200);
  if (!mag.begin()) {
    Serial.println("HMC5883L not found! Check wiring and address.");
    while (1);
  }
  sensor_t sensor;
  mag.getSensor(&sensor);
  Serial.print("Sensor: "); Serial.println(sensor.name);
}

void loop() {
  sensors_event_t event;
  mag.getEvent(&event);
  // Heading in degrees (0 = North)
  float heading = atan2(event.magnetic.y, event.magnetic.x) * 180.0 / PI;
  if (heading < 0) heading += 360;
  Serial.print("Heading: "); Serial.print(heading, 1); Serial.println("°");
  // Raw field components
  Serial.print("X: "); Serial.print(event.magnetic.x); Serial.print(" µT  ");
  Serial.print("Y: "); Serial.print(event.magnetic.y); Serial.print(" µT  ");
  Serial.print("Z: "); Serial.println(event.magnetic.z);
  delay(200);
}

6. Arduino Code for QMC5883L

Install the QMC5883LCompass library by MPrograms from the Library Manager:

#include <QMC5883LCompass.h>

QMC5883LCompass compass;

void setup() {
  Serial.begin(115200);
  Wire.begin();
  compass.init();           // Connects to 0x0D, sets continuous mode
  compass.setMode(0x01,     // Continuous mode
                  0x0C,     // 200 Hz ODR
                  0x10,     // ±8 Gauss range
                  0x00);    // Oversampling ratio 512
}

void loop() {
  compass.read();
  int x = compass.getX();
  int y = compass.getY();
  int z = compass.getZ();
  // Heading
  float heading = atan2((float)y, (float)x) * 180.0 / PI;
  if (heading < 0) heading += 360.0;
  Serial.print("Heading: "); Serial.print(heading, 1); Serial.print("°  ");
  Serial.print("X: "); Serial.print(x); Serial.print("  ");
  Serial.print("Y: "); Serial.print(y); Serial.print("  ");
  Serial.print("Z: "); Serial.println(z);
  delay(100);
}

The QMC5883L returns raw 16-bit signed integers in LSB units. To convert to µT: multiply by the scale factor for your chosen range (±2G: 0.0833 µT/LSB; ±8G: 0.333 µT/LSB).

GY-BME280-3.3 Precision Altimeter Sensor Module

Pair your magnetometer with a BME280 for weather-aware navigation projects. Shares the I2C bus at a different address, so both sensors work simultaneously.

View on Zbotic

7. Magnetometer Calibration: Hard-Iron and Soft-Iron

Without calibration, a magnetometer compass will be wildly inaccurate. Calibration corrects two types of distortion:

Hard-Iron Distortion

Caused by permanently magnetised materials near the sensor (speaker magnets, steel chassis, PCB copper pours). This creates a constant offset in all readings, shifting the measurement sphere off-centre. Correction: find the offset by rotating the sensor through all orientations and computing the centre of the data ellipsoid.

// Hard-iron calibration: collect data while rotating slowly
// in all orientations (flip upside down, rotate 360° on each axis)
int xMin = 32767, xMax = -32768;
int yMin = 32767, yMax = -32768;
// After collection:
float xOffset = (xMax + xMin) / 2.0;
float yOffset = (yMax + yMin) / 2.0;
// Apply: corrX = rawX - xOffset; corrY = rawY - yOffset;

Soft-Iron Distortion

Caused by magnetically permeable materials (soft iron, certain alloys) that distort the shape of the Earth’s field around the sensor. This stretches the sphere of raw measurements into an ellipsoid. Correcting it requires a 3×3 scaling matrix, but for most maker applications, a simple axis scaling approximation is sufficient:

// Soft-iron scale factors (computed from ellipsoid axes)
float xScale = 2.0 / (xMax - xMin);
float yScale = 2.0 / (yMax - yMin);
// Apply: scaledX = (rawX - xOffset) * xScale
//        scaledY = (rawY - yOffset) * yScale

After full calibration, the heading formula gives results accurate to within 2–5° in environments with moderate magnetic interference. For best results, calibrate the sensor in its final mounted position (inside your robot, PCB assembly, etc.) rather than in the open air.

8. Tilt Compensation with Accelerometer

A plain magnetometer compass only works when the sensor is perfectly horizontal. Tilting it changes the projection of the Earth’s magnetic field on the X-Y plane, giving large heading errors. The fix is tilt compensation using accelerometer data:

// Roll and pitch from accelerometer (in radians)
float roll  = atan2(ay, az);
float pitch = atan2(-ax, sqrt(ay*ay + az*az));

// Tilt-compensated magnetic components
float Xh = mx * cos(pitch) + mz * sin(pitch);
float Yh = mx * sin(roll) * sin(pitch) + my * cos(roll)
           - mz * sin(roll) * cos(pitch);

// Tilt-compensated heading
float heading = atan2(Yh, Xh) * 180.0 / PI;
if (heading < 0) heading += 360.0;

Where ax, ay, az are accelerometer readings in g, and mx, my, mz are calibrated magnetometer readings. The GY-273 does not have an accelerometer, so combine it with an ADXL345, MPU6050, or MPU9250 for tilt-compensated operation.

9. Magnetic Declination for Indian Cities

Magnetic north differs from geographic (true) north by the magnetic declination angle, which varies by location. In India, the declination is westward (negative), meaning magnetic north points slightly west of true north. Add the declination to your compass heading to get true north:

In code: trueHeading = magneticHeading + declination; where declination is positive for East, negative for West. Look up your exact declination at ngdc.noaa.gov/geomag/calculators/magcalc.shtml.

BMP280 Barometric Pressure and Altitude Sensor

Combine with your magnetometer for a full compass and altimeter setup. Perfect for hiking GPS loggers and drone navigation systems.

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10. Troubleshooting Common Problems