HMC5883L Magnetometer X, Z values constant, only Y value Changes

Question

I have a HMC5883L module connected to an Arduino Mega 2560 via +5, GND, SCL, SDA. The Arduino code is from the MagMaster-master example, as follows:

#include "Wire.h"
#include "HMC5883L.h"
HMC5883L compass; //Copy the folder "HMC5883L" in the folder "C:\Program Files\Arduino\libraries" and restart the arduino IDE.
float xv, yv, zv;
void setup()
{

  Serial.begin(9600);
  Wire.begin();

  compass = HMC5883L();

  setupHMC5883L();

}
void loop()
{
  getHeading();
Serial.flush(); 
  Serial.print(xv); 
  Serial.print(",");
  Serial.print(yv);
  Serial.print(",");
  Serial.print(zv);
  Serial.println();
delay(100); 
}
void setupHMC5883L()
{

  compass.SetScale(0.88);
  compass.SetMeasurementMode(Measurement_Continuous);
}
void getHeading()
{ 
  MagnetometerRaw raw = compass.ReadRawAxis();
  xv = (float)raw.XAxis;
  yv = (float)raw.YAxis;
  zv = (float)raw.ZAxis;
}

When I run the code, I get the following output on the serial monitor

-15872.00,-27601.00,1.00
-15872.00,3264.00,1.00
-15872.00,19536.00,1.00
-15872.00,-18208.00,1.00
-15872.00,12401.00,1.00
-15872.00,-27647.00,1.00
-15872.00,1170.00,1.00
-15872.00,17442.00,1.00
-15872.00,-21326.00,1.00
-15872.00,7235.00,1.00
-15872.00,21715.00,1.00
-15872.00,-15261.00,1.00
-15872.00,15604.00,1.00
-15872.00,-22396.00,1.00
-15872.00,7189.00,1.00
-15872.00,23717.00,1.00
-15872.00,-13259.00,1.00
-15872.00,14534.00,1.00
-15872.00,-24490.00,1.00
-15872.00,3303.00,1.00
-15872.00,17527.00,1.00
-15872.00,-20473.00,1.00
-15872.00,9368.00,1.00
-15872.00,26664.00,1.00
-15872.00,-8008.00,1.00
-15872.00,8265.00,1.00
-15872.00,23769.00,1.00
-15872.00,-14231.00,1.00
-15872.00,13562.00,1.00
-15872.00,-24438.00,1.00
-15872.00,3099.00,1.00
-15872.00,17579.00,1.00
-15872.00,-19397.00,1.00
-15872.00,11468.00,1.00

As can be seen from the above, only the Y (middle column) values change when I move the sensor around. If I plot these values in Excel, I get a plot that looks like this:

I have looked through the code, and the HMC5883L library code (below) and nothing seems amiss. I tried a different HMC5883L module and got the same (bad) result. I know I must be doing something wrong, but I can't for the life of me figure it out. Any hints would be appreciated! ;-)

HMC5883L.cpp:

/*
HMC5883L.cpp - Class file for the HMC5883L Triple Axis Magnetometer Arduino Library.
Copyright (C) 2011 Love Electronics (loveelectronics.co.uk)/ 2012 bildr.org (Arduino 1.0 compatible)
This program is free software: you can redistribute it and/or modify
it under the terms of the version 3 GNU General Public License as
published by the Free Software Foundation.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
WARNING: THE HMC5883L IS NOT IDENTICAL TO THE HMC5883!
 Datasheet for HMC5883L:
 http://www51.honeywell.com/aero/common/documents/myaerospacecatalog-documents/Defense_Brochures-documents/HMC5883L_3-Axis_Digital_Compass_IC.pdf
*/
#include <Arduino.h> 
#include "HMC5883L.h"
HMC5883L::HMC5883L()
{
  m_Scale = 1;
}
MagnetometerRaw HMC5883L::ReadRawAxis()
{
  uint8_t* buffer = Read(DataRegisterBegin, 6);
  MagnetometerRaw raw = MagnetometerRaw();
  raw.XAxis = (buffer[0] << 8) | buffer[1];
  raw.ZAxis = (buffer[2] << 8) | buffer[3];
  raw.YAxis = (buffer[4] << 8) | buffer[5];
  return raw;
}
MagnetometerScaled HMC5883L::ReadScaledAxis()
{
  MagnetometerRaw raw = ReadRawAxis();
  MagnetometerScaled scaled = MagnetometerScaled();
  scaled.XAxis = raw.XAxis * m_Scale;
  scaled.ZAxis = raw.ZAxis * m_Scale;
  scaled.YAxis = raw.YAxis * m_Scale;
  return scaled;
}
int HMC5883L::SetScale(float gauss)
{
    uint8_t regValue = 0x00;
    if(gauss == 0.88)
    {
        regValue = 0x00;
        m_Scale = 0.73;
    }
    else if(gauss == 1.3)
    {
        regValue = 0x01;
        m_Scale = 0.92;
    }
    else if(gauss == 1.9)
    {
        regValue = 0x02;
        m_Scale = 1.22;
    }
    else if(gauss == 2.5)
    {
        regValue = 0x03;
        m_Scale = 1.52;
    }
    else if(gauss == 4.0)
    {
        regValue = 0x04;
        m_Scale = 2.27;
    }
    else if(gauss == 4.7)
    {
        regValue = 0x05;
        m_Scale = 2.56;
    }
    else if(gauss == 5.6)
    {
        regValue = 0x06;
        m_Scale = 3.03;
    }
    else if(gauss == 8.1)
    {
        regValue = 0x07;
        m_Scale = 4.35;
    }
    else
        return ErrorCode_1_Num;
// Setting is in the top 3 bits of the register.
regValue = regValue &lt;&lt; 5;
Write(ConfigurationRegisterB, regValue);

}
int HMC5883L::SetMeasurementMode(uint8_t mode)
{
    Write(ModeRegister, mode);
}
void HMC5883L::Write(int address, int data)
{
  Wire.beginTransmission(HMC5883L_Address);
  Wire.write(address);
  Wire.write(data);
  Wire.endTransmission();
}
uint8_t* HMC5883L::Read(int address, int length)
{
  Wire.beginTransmission(HMC5883L_Address);
  Wire.write(address);
  Wire.endTransmission();
Wire.beginTransmission(HMC5883L_Address);
  Wire.requestFrom(HMC5883L_Address, length);
uint8_t buffer[length];
  if(Wire.available() == length)
  {
      for(uint8_t i = 0; i < length; i++)
      {
          buffer[i] = Wire.read();
      }
  }
  Wire.endTransmission();
return buffer;
}
char* HMC5883L::GetErrorText(int errorCode)
{
    if(ErrorCode_1_Num == 1)
        return ErrorCode_1;
return &quot;Error not defined.&quot;;

}

HMC5883L.h:

/*
HMC5883L.h - Header file for the HMC5883L Triple Axis Magnetometer Arduino Library.
Copyright (C) 2011 Love Electronics (loveelectronics.co.uk) / 2012 bildr.org (Arduino 1.0 compatible)
This program is free software: you can redistribute it and/or modify
it under the terms of the version 3 GNU General Public License as
published by the Free Software Foundation.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
WARNING: THE HMC5883L IS NOT IDENTICAL TO THE HMC5883!
 Datasheet for HMC5883L:
 http://www51.honeywell.com/aero/common/documents/myaerospacecatalog-documents/Defense_Brochures-documents/HMC5883L_3-Axis_Digital_Compass_IC.pdf
*/
#ifndef HMC5883L_h
#define HMC5883L_h
#include <Arduino.h>
#include <Wire.h>
#define HMC5883L_Address 0x1E
#define ConfigurationRegisterA 0x00
#define ConfigurationRegisterB 0x01
#define ModeRegister 0x02
#define DataRegisterBegin 0x03
#define Measurement_Continuous 0x00
#define Measurement_SingleShot 0x01
#define Measurement_Idle 0x03
#define ErrorCode_1 "Entered scale was not valid, valid gauss values are: 0.88, 1.3, 1.9, 2.5, 4.0, 4.7, 5.6, 8.1"
#define ErrorCode_1_Num 1
struct MagnetometerScaled
{
    float XAxis;
    float YAxis;
    float ZAxis;
};
struct MagnetometerRaw
{
    int XAxis;
    int YAxis;
    int ZAxis;
};
class HMC5883L
{
    public:
      HMC5883L();
  MagnetometerRaw ReadRawAxis();
  MagnetometerScaled ReadScaledAxis();

  int SetMeasurementMode(uint8_t mode);
  int SetScale(float gauss);

  char* GetErrorText(int errorCode);

protected:
  void Write(int address, int byte);
  uint8_t* Read(int address, int length);

private:
  float m_Scale;

};
#endif

Is this the Adafruit module? If so I would follow their tutorial step by step before breaking out on your own. Also, know that magnetometers are more difficult to align and use then, say, an accelerometer or gyroscope. — st2000, Jan 12 '21 at 00:36
No, it's not - just a typical GY-273 clone. I did look at the Adafruit tutorial, but it just covers the same ground. — starship15, Jan 12 '21 at 02:04
If it is not too big of an investment, I would buy the HW so as to be able to use the Adafruit tutorial exactly. Or, if you can, look for a working example that fits your HW situation. I've only worked w/the STMicro magnetometers & IMUs. Their magnetometers are very sensitive and need to be aligned either by setting registers inside the chip or externally in the SW. Regardless, there are usually many registers needing configuration before meaningful data is read out. Meanwhile, in the short term, perhaps someone will spot something missing in your code preventing your HMC5883L from working. — st2000, Jan 12 '21 at 15:50
Oh, do make sure that all your libraries are up to date. I know you may have heard this many times. But more often than not, code created for the Arduino by other hackers is only truly vetted after many others have tested and improved the code. — st2000, Jan 12 '21 at 15:53

HMC5883L Magnetometer X, Z values constant, only Y value Changes

0 Answers0