QMC5883L | Technology Tutorials

In this video lesson we show how to calibrate a QMC5883L 3-Axis magnetometer using python and PyQt5. The program presents the user with a visual representation of the magnetic vector, allowing more precise calibration of the sensors. We are using the GY-87 module, and it is connected like this:

MPU6050 — Schematic for connecting the GY-87 module to the Arduino

This is the simple code on the Arduino side, sending the raw magnetometer data:

#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
#include <Wire.h>
#include <QMC5883LCompass.h>
int x,y,z;
Adafruit_MPU6050 mpu;
QMC5883LCompass compass;
void setup() {
Serial.begin(115200);
mpu.begin();
mpu.setI2CBypass(true);
compass.init();
}
void loop() {
 compass.read();
 x = compass.getX();
 y = compass.getY();
 z = compass.getZ();
Serial.print(x);
Serial.print(',');
Serial.print(y);
Serial.print(',');
Serial.println(z);
 delay(100);
}

#include <Adafruit_MPU6050.h>

#include <Adafruit_Sensor.h>

#include <Wire.h>

#include <QMC5883LCompass.h>

int x,y,z;

Adafruit_MPU6050 mpu;

QMC5883LCompass compass;

void setup() {

Serial.begin(115200);

mpu.begin();

mpu.setI2CBypass(true);

compass.init();

}

void loop() {

compass.read();

x = compass.getX();

y = compass.getY();

z = compass.getZ();

Serial.print(x);

Serial.print(',');

Serial.print(y);

Serial.print(',');

Serial.println(z);

delay(100);

}

This is the calibration code, running on the Python side;

import serial
import numpy as np
from PyQt5 import QtWidgets, QtCore
import pyqtgraph as pg
serialPort = 'COM8'
baudRate =115200
to =.1
ser =serial.Serial(serialPort, baudRate, timeout=to)
maxPoints = 2000
xRaw = np.empty(0)
yRaw = np.empty(0)
zRaw = np.empty(0)

xCal = np.empty(0)
yCal = np.empty(0)
zCal = np.empty(0)

calibrated = False
offsets = np.zeros(3)
scales = np.ones(3)

app = QtWidgets.QApplication([])
mainWindow = QtWidgets.QWidget()
mainWindow.setWindowTitle("Magnetometer Calibratioin")
mainLayout =QtWidgets.QVBoxLayout()
mainWindow.setLayout(mainLayout)

statusLabel = QtWidgets.QLabel("Program Running: Not Calibrated")
statusLabel.setAlignment(QtCore.Qt.AlignCenter)
statusLabel.setStyleSheet("color: green; font-weight: bold; font-size: 20px;")
mainLayout.addWidget(statusLabel)

minMaxLabel=QtWidgets.QLabel("Min/Max: N/A")
minMaxLabel.setAlignment(QtCore.Qt.AlignCenter)
minMaxLabel.setStyleSheet("color: green; font-weight: bold; font-size: 16px;")
mainLayout.addWidget(minMaxLabel)

calibrateButton = QtWidgets.QPushButton("Start Calibration")
calibrateButton.setCheckable(True)
mainLayout.addWidget(calibrateButton)


plotLayout =QtWidgets.QGridLayout()
mainLayout.addLayout(plotLayout)
xyPlot = pg.PlotWidget(title="XY Plane")
yzPlot = pg.PlotWidget(title="YZ Plane")
xzPlot = pg.PlotWidget(title="XZ Plane")
for plot in [xyPlot, yzPlot, xzPlot]:
    plot.setAspectLocked(True)
    plot.showGrid(x=True, y=True)
    plot.setMinimumSize(300,300)
plotLayout.addWidget(xyPlot, 0,0)
plotLayout.addWidget(yzPlot, 0,1)
plotLayout.addWidget(xzPlot, 1,0)

xyScatter = pg.ScatterPlotItem(size=5)
yzScatter = pg.ScatterPlotItem(size=5)
xzScatter = pg.ScatterPlotItem(size=5)

xyPlot.addItem(xyScatter)
yzPlot.addItem(yzScatter)
xzPlot.addItem(xzScatter)

def toggleCalibration():
    global calibrated, xRaw, yRaw, zRaw, xCal, yCal, zCal, offsets, scales
    
    if calibrateButton.isChecked():
        calibrateButton.setText("Stop Calibration")
        statusLabel.setText("Mode: Calibration")
        statusLabel.setStyleSheet("color: red; font-weight: bold; font-size: 20px;")
        minMaxLabel.setText("Min/Max: collecting . . .")
        minMaxLabel.setStyleSheet("color: red; font-weight: bold; font-size: 16px;")
        calibrated = False
        xRaw = np.empty(0)
        yRaw = np.empty(0)
        zRaw = np.empty(0)
    if not calibrateButton.isChecked():
        calibrateButton.setText("Start Calibration")
        statusLabel.setText("Mode: Calibrated")
        statusLabel.setStyleSheet("color: green; font-weight: bold; font-size: 20px;")
        
        rawData = np.column_stack((xRaw,yRaw,zRaw))
        minVals = np.min(rawData, axis=0)
        maxVals = np.max(rawData, axis=0)
        offsets = (maxVals + minVals)/2
        scales = 2.0/(maxVals-minVals)
        minMaxLabel.setStyleSheet("color: green; font-weight: bold; font-size: 16px;")
        minMaxLabel.setText("Min(x,y,z: "+str(minVals.round(2))+" Max(x,y,z): "
                            +str(maxVals.round(2))+" Offsets(x,y,z): "+str(offsets.round(2))
                            +"Scales(x,y,z): "+str(scales.round(5)))
        print("Calibration Completed.")
        print("Offsets: ", offsets)
        print("Scales: ", scales)
        
        xCal = np.empty(0)
        yCal = np.empty(0)
        zCal = np.empty(0)
        calibrated = True

calibrateButton.clicked.connect(toggleCalibration)
        
def updatePlot():
    global xRaw, yRaw, zRaw, xCal, yCal, zCal
    if ser.in_waiting > 0:
        try:
            line= ser.readline().decode('utf-8').strip()
            values = line.split(',')
            if len(values)==3:
                x = float(values[0])
                y = float(values[1])
                z = float(values[2])
                if not calibrated:
                    xRaw =np.append(xRaw, x)[-maxPoints:]
                    yRaw =np.append(yRaw, y)[-maxPoints:]
                    zRaw =np.append(zRaw, z)[-maxPoints:]
                    xyScatter.setData(x=xRaw, y=yRaw, brush=pg.mkBrush(0,0,255,255))
                    yzScatter.setData(x=yRaw, y=zRaw, brush=pg.mkBrush(0,255,0,255))
                    xzScatter.setData(x=xRaw, y=zRaw, brush=pg.mkBrush(255,0,0,255))
                    
                    if len(xRaw)>10:
                        minVals = np.min(np.column_stack((xRaw,yRaw,zRaw)),axis=0)
                        maxVals = np.max(np.column_stack((xRaw,yRaw,zRaw)),axis=0)
                        
                        minMaxLabel.setStyleSheet("color: red; font-weight: bold; font-size: 16px;")
                        minMaxLabel.setText("Min(x,y,z: "+str(minVals.round(2))+" Max(x,y,z): "
                            +str(maxVals.round(2)))
                
                if calibrated:
                    xC= (x - offsets[0])*scales[0]
                    yC= (y - offsets[1])*scales[1]
                    zC= (z - offsets[2])*scales[2]
                    
                    xCal = np.append(xCal, xC)[-maxPoints:]
                    yCal = np.append(yCal, yC)[-maxPoints:]
                    zCal = np.append(zCal, zC)[-maxPoints:]
                    
                    xyScatter.setData(x=xCal, y=yCal, brush=pg.mkBrush(0,0,255,120))
                    yzScatter.setData(x=yCal, y=zCal, brush=pg.mkBrush(0,255,0,120))
                    xzScatter.setData(x=xCal, y=zCal, brush=pg.mkBrush(255,0,0,120))             
        
        except Exception as e:
            print("Parse Error: ", e)

plotTimer =QtCore.QTimer()
plotTimer.timeout.connect(updatePlot)
plotTimer.start(50)
mainWindow.show()
try:
    app.exec_()
finally:
    ser.close()

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import serial

import numpy as np

from PyQt5 import QtWidgets, QtCore

import pyqtgraph as pg

serialPort = 'COM8'

baudRate =115200

to =.1

ser =serial.Serial(serialPort, baudRate, timeout=to)

maxPoints = 2000

xRaw = np.empty(0)

yRaw = np.empty(0)

zRaw = np.empty(0)

xCal = np.empty(0)

yCal = np.empty(0)

zCal = np.empty(0)

calibrated = False

offsets = np.zeros(3)

scales = np.ones(3)

app = QtWidgets.QApplication([])

mainWindow = QtWidgets.QWidget()

mainWindow.setWindowTitle("Magnetometer Calibratioin")

mainLayout =QtWidgets.QVBoxLayout()

mainWindow.setLayout(mainLayout)

statusLabel = QtWidgets.QLabel("Program Running: Not Calibrated")

statusLabel.setAlignment(QtCore.Qt.AlignCenter)

statusLabel.setStyleSheet("color: green; font-weight: bold; font-size: 20px;")

mainLayout.addWidget(statusLabel)

minMaxLabel=QtWidgets.QLabel("Min/Max: N/A")

minMaxLabel.setAlignment(QtCore.Qt.AlignCenter)

minMaxLabel.setStyleSheet("color: green; font-weight: bold; font-size: 16px;")

mainLayout.addWidget(minMaxLabel)

calibrateButton = QtWidgets.QPushButton("Start Calibration")

calibrateButton.setCheckable(True)

mainLayout.addWidget(calibrateButton)

plotLayout =QtWidgets.QGridLayout()

mainLayout.addLayout(plotLayout)

xyPlot = pg.PlotWidget(title="XY Plane")

yzPlot = pg.PlotWidget(title="YZ Plane")

xzPlot = pg.PlotWidget(title="XZ Plane")

for plot in [xyPlot, yzPlot, xzPlot]:

plot.setAspectLocked(True)

plot.showGrid(x=True, y=True)

plot.setMinimumSize(300,300)

plotLayout.addWidget(xyPlot, 0,0)

plotLayout.addWidget(yzPlot, 0,1)

plotLayout.addWidget(xzPlot, 1,0)

xyScatter = pg.ScatterPlotItem(size=5)

yzScatter = pg.ScatterPlotItem(size=5)

xzScatter = pg.ScatterPlotItem(size=5)

xyPlot.addItem(xyScatter)

yzPlot.addItem(yzScatter)

xzPlot.addItem(xzScatter)

def toggleCalibration():

global calibrated, xRaw, yRaw, zRaw, xCal, yCal, zCal, offsets, scales

if calibrateButton.isChecked():

calibrateButton.setText("Stop Calibration")

statusLabel.setText("Mode: Calibration")

statusLabel.setStyleSheet("color: red; font-weight: bold; font-size: 20px;")

minMaxLabel.setText("Min/Max: collecting . . .")

minMaxLabel.setStyleSheet("color: red; font-weight: bold; font-size: 16px;")

calibrated = False

xRaw = np.empty(0)

yRaw = np.empty(0)

zRaw = np.empty(0)

if not calibrateButton.isChecked():

calibrateButton.setText("Start Calibration")

statusLabel.setText("Mode: Calibrated")

statusLabel.setStyleSheet("color: green; font-weight: bold; font-size: 20px;")

rawData = np.column_stack((xRaw,yRaw,zRaw))

minVals = np.min(rawData, axis=0)

maxVals = np.max(rawData, axis=0)

offsets = (maxVals + minVals)/2

scales = 2.0/(maxVals-minVals)

minMaxLabel.setStyleSheet("color: green; font-weight: bold; font-size: 16px;")

minMaxLabel.setText("Min(x,y,z: "+str(minVals.round(2))+" Max(x,y,z): "

+str(maxVals.round(2))+" Offsets(x,y,z): "+str(offsets.round(2))

+"Scales(x,y,z): "+str(scales.round(5)))

print("Calibration Completed.")

print("Offsets: ", offsets)

print("Scales: ", scales)

xCal = np.empty(0)

yCal = np.empty(0)

zCal = np.empty(0)

calibrated = True

calibrateButton.clicked.connect(toggleCalibration)

def updatePlot():

global xRaw, yRaw, zRaw, xCal, yCal, zCal

if ser.in_waiting > 0:

try:

line= ser.readline().decode('utf-8').strip()

values = line.split(',')

if len(values)==3:

x = float(values[0])

y = float(values[1])

z = float(values[2])

if not calibrated:

xRaw =np.append(xRaw, x)[-maxPoints:]

yRaw =np.append(yRaw, y)[-maxPoints:]

zRaw =np.append(zRaw, z)[-maxPoints:]

xyScatter.setData(x=xRaw, y=yRaw, brush=pg.mkBrush(0,0,255,255))

yzScatter.setData(x=yRaw, y=zRaw, brush=pg.mkBrush(0,255,0,255))

xzScatter.setData(x=xRaw, y=zRaw, brush=pg.mkBrush(255,0,0,255))

if len(xRaw)>10:

minVals = np.min(np.column_stack((xRaw,yRaw,zRaw)),axis=0)

maxVals = np.max(np.column_stack((xRaw,yRaw,zRaw)),axis=0)

minMaxLabel.setStyleSheet("color: red; font-weight: bold; font-size: 16px;")

minMaxLabel.setText("Min(x,y,z: "+str(minVals.round(2))+" Max(x,y,z): "

+str(maxVals.round(2)))

if calibrated:

xC= (x - offsets[0])*scales[0]

yC= (y - offsets[1])*scales[1]

zC= (z - offsets[2])*scales[2]

xCal = np.append(xCal, xC)[-maxPoints:]

yCal = np.append(yCal, yC)[-maxPoints:]

zCal = np.append(zCal, zC)[-maxPoints:]

xyScatter.setData(x=xCal, y=yCal, brush=pg.mkBrush(0,0,255,120))

yzScatter.setData(x=yCal, y=zCal, brush=pg.mkBrush(0,255,0,120))

xzScatter.setData(x=xCal, y=zCal, brush=pg.mkBrush(255,0,0,120))

except Exception as e:

print("Parse Error: ", e)

plotTimer =QtCore.QTimer()

plotTimer.timeout.connect(updatePlot)

plotTimer.start(50)

mainWindow.show()

try:

app.exec_()

finally:

ser.close()

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Python PyQt5 Magnetometer Calibration Program

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