QMC5883l not giving accurate reading

Projects Networking, Protocols, and Devices
1

Hi, I am trying to use the QMC5883l compass, however, the readings from the compass are clearly inaccurate. If the heading it shows is 200 degrees, and I rotate it ~90 deg CCW, the heading only changes by 40-50 deg. However, if it reads a heading below 100, and I move the compass very slightly, by around 10 deg, the heading jumps by 90 - 100 deg on the compass. I doubt there is an issue with the code because I am using the code provided by the DFRobot_5883 library. I have already factored in magnetic declination, but is any other calibration required?

/*!
 * @file getCompassdata.ino
 * @brief Output the compass data
 * @copyright   Copyright (c) 2010 DFRobot Co.Ltd (http://www.dfrobot.com)
 * @license     The MIT License (MIT)
 * @author      [dexian.huang](952838602@qq.com)
 * @version  V1.0
 * @date  2017-7-3
 * @url https://github.com/DFRobot/DFRobot_QMC5883
 */
#include <DFRobot_QMC5883.h>

DFRobot_QMC5883 compass(&Wire, /*I2C addr*/0X0D);

void setup()
{
  Serial.begin(115200);
  while (!compass.begin())
  {
    Serial.println("Could not find a valid 5883 sensor, check wiring!");
    delay(500);
  }

  if(compass.isHMC())
  {
    Serial.println("Initialize HMC5883");

    //Set/get the compass signal gain range, default to be 1.3 Ga
    // compass.setRange(HMC5883L_RANGE_1_3GA);
    // Serial.print("compass range is:");
    // Serial.println(compass.getRange());

    //Set/get measurement mode
    // compass.setMeasurementMode(HMC5883L_CONTINOUS);
    // Serial.print("compass measurement mode is:");
    // Serial.println(compass.getMeasurementMode());

    //Set/get the data collection frequency of the sensor
    // compass.setDataRate(HMC5883L_DATARATE_15HZ);
    // Serial.print("compass data rate is:");
    // Serial.println(compass.getDataRate());

    //Get/get sensor status
    // compass.setSamples(HMC5883L_SAMPLES_8);
    // Serial.print("compass samples is:");
    // Serial.println(compass.getSamples());
  }
  else if(compass.isQMC())
  {
    Serial.println("Initialize QMC5883");
    // compass.setRange(QMC5883_RANGE_2GA);
    // Serial.print("compass range is:");
    // Serial.println(compass.getRange());

    // compass.setMeasurementMode(QMC5883_CONTINOUS);
    // Serial.print("compass measurement mode is:");
    // Serial.println(compass.getMeasurementMode());

    // compass.setDataRate(QMC5883_DATARATE_50HZ);
    // Serial.print("compass data rate is:");
    // Serial.println(compass.getDataRate());

    // compass.setSamples(QMC5883_SAMPLES_8);
    // Serial.print("compass samples is:");
    // Serial.println(compass.getSamples());
  }
  else if(compass.isVCM())
  {
    Serial.println("Initialize VCM5883L");
    // compass.setMeasurementMode(VCM5883L_CONTINOUS);
    // Serial.print("compass measurement mode is:");
    // Serial.println(compass.getMeasurementMode());

    // compass.setDataRate(VCM5883L_DATARATE_200HZ);
    // Serial.print("compass data rate is:");
    // Serial.println(compass.getDataRate());
  }
  delay(1000);
}
void loop()
{
  /**
   * @brief  Set declination angle on your location and fix heading
   * @n      You can find your declination on: http://magnetic-declination.com/
   * @n      (+) Positive or (-) for negative
   * @n      For Bytom / Poland declination angle is 4'26E (positive)
   * @n      Formula: (deg + (min / 60.0)) / (180 / PI);
   */
  float declinationAngle = (11.0 - (41.0 / 60.0)) / (180 / PI);
  compass.setDeclinationAngle(declinationAngle);
  sVector_t mag = compass.readRaw();
  compass.getHeadingDegrees();
  /*Serial.print("X:");
  Serial.print(mag.XAxis);
  Serial.print(" Y:");
  Serial.print(mag.YAxis);
  Serial.print(" Z:");
  Serial.println(mag.ZAxis);*/
  Serial.print("Degress = ");
  Serial.println(mag.HeadingDegress);
  delay(100);
}
2

It seems tha there are QMC5883 and HMC5883 devices and they are not the same. See here,

3

Yes, I was aware of that and I am using a library made for the QMC5883. I ran a code to check the I2C address to make sure, and the address was 0X0D, which means it should be QMC5883. Is there a better library that you would recommend?

4

Magnetometers must be calibrated before they can be used as compasses, and must held level in use and kept away from iron objects, magnetized materials and current carrying wires.

Quick and dirty calibration: Accelerometer Calibration II: Simple Methods | Chionotech

Much better overview and tutorial: Tutorial: How to calibrate a compass (and accelerometer) with Arduino | Underwater Arduino Data Loggers