Category Archives: Arduino

In this video lesson we add a low pass filter to our calibration and digital compass program. This allows more precise calibration, and removes the jitter from the digital compass display. We continue to use the QMC5883L 3-Axis Magnetometer, which is on our GY-87 IMU module. We are using the following schematic for our project:

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

We collect the data using the GY-87 connected to an Arduino. Below is the simple program which takes the magnetometer data and sends it to the serial port.

#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);

}

The code for the Python side to do the calibration and display a Digital Compass is:

import serial
import numpy as np
from PyQt5 import QtWidgets, QtCore, QtGui
import pyqtgraph as pg
import math
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)
x=0
y=0
z=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)

headingPlot = pg.PlotWidget(title="Compass Heading")
headingPlot.setAspectLocked(True)
headingPlot.showGrid(x=True, y=True)
headingPlot.setMinimumSize(300,300)
headingPlot.hideAxis('left')
headingPlot.hideAxis('bottom')
plotLayout.addWidget(headingPlot,1,1)

compassCircle=pg.EllipseROI([-1.5,-1.5],[3.,3.],pen=pg.mkPen('b',width=4),movable=False, resizable=False)
headingPlot.addItem(compassCircle)
compassCircle.removeHandle(0)
compassCircle.removeHandle(0)
compassCircle.setZValue(0)

arrowShaft=pg.PlotCurveItem( x=[0,0],y=[0,1.5],pen=pg.mkPen('r',width=4))
headingPlot.addItem(arrowShaft)
dot=pg.ScatterPlotItem(pos=[(0,1.5)],width=4,size=10,pen=pg.mkPen('y'),brush=pg.mkBrush('y'))
dot.setZValue(1)
headingPlot.addItem(dot)

for angle, label in zip([0,90,180,270],['E','N','W','S']):
    rad = angle/360*2*math.pi
    xPos = np.cos(rad)*1.8
    yPos = np.sin(rad)*1.8
    text=pg.TextItem(label, anchor = (.5,.5), color='g')
    font=QtGui.QFont()
    font.setBold(True)
    font.setPointSize(12)
    text.setFont(font)
    text.setPos(xPos,yPos)
    headingPlot.addItem(text)
    
liveHeading = pg.TextItem("Heading: 0.0\u00B0",anchor= (.5,.5),color='w')
liveHeading.setFont(font)
liveHeading.setPos(0,-2.2)
liveHeading.setZValue(1)
headingPlot.addItem(liveHeading)


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, x, y ,z
    if ser.in_waiting > 0:
        try:
            line= ser.readline().decode('utf-8').strip()
            values = line.split(',')
            if len(values)==3:
                x = x*.75 + float(values[0])*.25
                y = y*.75 + float(values[1])*.25
                z = z*.75 + float(values[2])*.25
                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))
                    
                    headRad= math.atan2(yC,xC)
                    headDeg=(headRad*360/2/math.pi)%360
                    compassRad= -headRad+ math.pi/2
                    compassDeg = (-headDeg + 90)%360
                    xDot=1.5*math.cos(compassRad)
                    yDot=1.5*math.sin(compassRad)
                    dot.setData(pos=([(xDot,yDot)]))
                    arrowShaft.setData(x=[0,xDot],y=[0,yDot])
                    liveHeading.setText("Heading: "+str(int(headDeg))+"\u00B0")      
        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, QtGui

import pyqtgraph as pg

import math

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)

x=0

y=0

z=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)

headingPlot = pg.PlotWidget(title="Compass Heading")

headingPlot.setAspectLocked(True)

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

headingPlot.setMinimumSize(300,300)

headingPlot.hideAxis('left')

headingPlot.hideAxis('bottom')

plotLayout.addWidget(headingPlot,1,1)

compassCircle=pg.EllipseROI([-1.5,-1.5],[3.,3.],pen=pg.mkPen('b',width=4),movable=False, resizable=False)

headingPlot.addItem(compassCircle)

compassCircle.removeHandle(0)

compassCircle.setZValue(0)

arrowShaft=pg.PlotCurveItem( x=[0,0],y=[0,1.5],pen=pg.mkPen('r',width=4))

headingPlot.addItem(arrowShaft)

dot=pg.ScatterPlotItem(pos=[(0,1.5)],width=4,size=10,pen=pg.mkPen('y'),brush=pg.mkBrush('y'))

dot.setZValue(1)

headingPlot.addItem(dot)

for angle, label in zip([0,90,180,270],['E','N','W','S']):

rad = angle/360*2*math.pi

xPos = np.cos(rad)*1.8

yPos = np.sin(rad)*1.8

text=pg.TextItem(label, anchor = (.5,.5), color='g')

font=QtGui.QFont()

font.setBold(True)

font.setPointSize(12)

text.setFont(font)

text.setPos(xPos,yPos)

headingPlot.addItem(text)

liveHeading = pg.TextItem("Heading: 0.0\u00B0",anchor= (.5,.5),color='w')

liveHeading.setFont(font)

liveHeading.setPos(0,-2.2)

liveHeading.setZValue(1)

headingPlot.addItem(liveHeading)

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, x, y ,z

if ser.in_waiting > 0:

try:

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

values = line.split(',')

if len(values)==3:

x = x*.75 + float(values[0])*.25

y = y*.75 + float(values[1])*.25

z = z*.75 + float(values[2])*.25

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))

headRad= math.atan2(yC,xC)

headDeg=(headRad*360/2/math.pi)%360

compassRad= -headRad+ math.pi/2

compassDeg = (-headDeg + 90)%360

xDot=1.5*math.cos(compassRad)

yDot=1.5*math.sin(compassRad)

dot.setData(pos=([(xDot,yDot)]))

arrowShaft.setData(x=[0,xDot],y=[0,yDot])

liveHeading.setText("Heading: "+str(int(headDeg))+"\u00B0")

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()

Arduino, Python

Calibrated Compass Display in Python and PyQt5

October 15, 2025 admin

In this video lesson we develop a Graphical Digital Compass using python and PyQt5. The data comes from a QMC5883L magnetometer connected to an arduino. The magnetometer is on the GY-87 IMU module. The arduino sends the raw data to python. With the raw data in Python, we then calibrate the sensor, and create a graphical representation of a digital compass. The circuit schematic we are using is:

The simple program for collecting the raw data on Arduino is:

#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);

}

On the python side, this is the code we developed which both calibrates the magnetometers, and displays a Digital Compass.

import serial
import numpy as np
from PyQt5 import QtWidgets, QtCore, QtGui
import pyqtgraph as pg
import math
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)
x=0
y=0
z=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)

headingPlot = pg.PlotWidget(title="Compass Heading")
headingPlot.setAspectLocked(True)
headingPlot.showGrid(x=True, y=True)
headingPlot.setMinimumSize(300,300)
headingPlot.hideAxis('left')
headingPlot.hideAxis('bottom')
plotLayout.addWidget(headingPlot,1,1)

compassCircle=pg.EllipseROI([-1.5,-1.5],[3.,3.],pen=pg.mkPen('b',width=4),movable=False, resizable=False)
headingPlot.addItem(compassCircle)
compassCircle.removeHandle(0)
compassCircle.removeHandle(0)
compassCircle.setZValue(0)

arrowShaft=pg.PlotCurveItem( x=[0,0],y=[0,1.5],pen=pg.mkPen('r',width=4))
headingPlot.addItem(arrowShaft)
dot=pg.ScatterPlotItem(pos=[(0,1.5)],width=4,size=10,pen=pg.mkPen('y'),brush=pg.mkBrush('y'))
dot.setZValue(1)
headingPlot.addItem(dot)

for angle, label in zip([0,90,180,270],['E','N','W','S']):
    rad = angle/360*2*math.pi
    xPos = np.cos(rad)*1.8
    yPos = np.sin(rad)*1.8
    text=pg.TextItem(label, anchor = (.5,.5), color='g')
    font=QtGui.QFont()
    font.setBold(True)
    font.setPointSize(12)
    text.setFont(font)
    text.setPos(xPos,yPos)
    headingPlot.addItem(text)
    
liveHeading = pg.TextItem("Heading: 0.0\u00B0",anchor= (.5,.5),color='w')
liveHeading.setFont(font)
liveHeading.setPos(0,-2.2)
liveHeading.setZValue(1)
headingPlot.addItem(liveHeading)


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))
                    
                    headRad=math.atan2(yC,xC)
                    headDeg=(headRad*360/2/math.pi)%360
                    compassRad= -headRad+ math.pi/2
                    compassDeg = (-headDeg + 90)%360
                    xDot=1.5*math.cos(compassRad)
                    yDot=1.5*math.sin(compassRad)
                    dot.setData(pos=([(xDot,yDot)]))
                    arrowShaft.setData(x=[0,xDot],y=[0,yDot])
                    liveHeading.setText("Heading: "+str(int(headDeg))+"\u00B0")
                    
                    
        
        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, QtGui

import pyqtgraph as pg

import math

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)

x=0

y=0

z=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)

headingPlot = pg.PlotWidget(title="Compass Heading")

headingPlot.setAspectLocked(True)

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

headingPlot.setMinimumSize(300,300)

headingPlot.hideAxis('left')

headingPlot.hideAxis('bottom')

plotLayout.addWidget(headingPlot,1,1)

compassCircle=pg.EllipseROI([-1.5,-1.5],[3.,3.],pen=pg.mkPen('b',width=4),movable=False, resizable=False)

headingPlot.addItem(compassCircle)

compassCircle.removeHandle(0)

compassCircle.setZValue(0)

arrowShaft=pg.PlotCurveItem( x=[0,0],y=[0,1.5],pen=pg.mkPen('r',width=4))

headingPlot.addItem(arrowShaft)

dot=pg.ScatterPlotItem(pos=[(0,1.5)],width=4,size=10,pen=pg.mkPen('y'),brush=pg.mkBrush('y'))

dot.setZValue(1)

headingPlot.addItem(dot)

for angle, label in zip([0,90,180,270],['E','N','W','S']):

rad = angle/360*2*math.pi

xPos = np.cos(rad)*1.8

yPos = np.sin(rad)*1.8

text=pg.TextItem(label, anchor = (.5,.5), color='g')

font=QtGui.QFont()

font.setBold(True)

font.setPointSize(12)

text.setFont(font)

text.setPos(xPos,yPos)

headingPlot.addItem(text)

liveHeading = pg.TextItem("Heading: 0.0\u00B0",anchor= (.5,.5),color='w')

liveHeading.setFont(font)

liveHeading.setPos(0,-2.2)

liveHeading.setZValue(1)

headingPlot.addItem(liveHeading)

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))

headRad=math.atan2(yC,xC)

headDeg=(headRad*360/2/math.pi)%360

compassRad= -headRad+ math.pi/2

compassDeg = (-headDeg + 90)%360

xDot=1.5*math.cos(compassRad)

yDot=1.5*math.sin(compassRad)

dot.setData(pos=([(xDot,yDot)]))

arrowShaft.setData(x=[0,xDot],y=[0,yDot])

liveHeading.setText("Heading: "+str(int(headDeg))+"\u00B0")

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()

Arduino, Python

Plotting X-Y-Z Magnetometer Data for Accurate Calibration

October 1, 2025 admin

In this video lesson we create a PyQt5 Widget in Python to help calibrate the QMC5883L 3-Axis Magnetometer on the GY-87 module. The Widget plots the data coming from the Magnetometer in real time to allow more accurate calibration.

This is the circuit schematic for our project:

This is the simple code for the arduino to generate the raw 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 code we run on the Python side to plot the raw data:

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)

app = QtWidgets.QApplication([])
mainWindow = QtWidgets.QWidget()
mainWindow.setWindowTitle("Magnetometer Calibratioin")
mainLayout =QtWidgets.QVBoxLayout()
mainWindow.setLayout(mainLayout)
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 updatePlot():
    global xRaw, yRaw, zRaw
    if ser.in_waiting > 0:
        try:
            line= ser.readline().decode('utf-8').strip()
            print(line)
            values = line.split(',')
            if len(values)==3:
                x = float(values[0])
                y = float(values[1])
                z = float(values[2])
                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(0,0,255,120))
                yzScatter.setData(x=yRaw, y=zRaw, brush=pg.mkBrush(0,255,0,120))
                xzScatter.setData(x=xRaw, y=zRaw, 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()

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)

app = QtWidgets.QApplication([])

mainWindow = QtWidgets.QWidget()

mainWindow.setWindowTitle("Magnetometer Calibratioin")

mainLayout =QtWidgets.QVBoxLayout()

mainWindow.setLayout(mainLayout)

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 updatePlot():

global xRaw, yRaw, zRaw

if ser.in_waiting > 0:

try:

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

print(line)

values = line.split(',')

if len(values)==3:

x = float(values[0])

y = float(values[1])

z = float(values[2])

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(0,0,255,120))

yzScatter.setData(x=yRaw, y=zRaw, brush=pg.mkBrush(0,255,0,120))

xzScatter.setData(x=xRaw, y=zRaw, 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()

Arduino

Calibrating a 3-Axis Magnetometer

September 20, 2025 admin

In this video lesson we show you how to calibrate the QMC5883L 3-axis magnetometer. The lesson is geared toward this specific magnetometer, but the procedure will be the same for any 3-axis magnetometer. We then use the calibrated reading to measure and calculate the magnetic heading of the device. With this, we have created a calibrated digital compass. In this lesson we are using the GY-87 module, which contains the QMC5883L magnetometer. We are connecting the module to the arduino using the following schematic:

In the video we develop two programs. The first program determines your sensor’s calibration constants. Then the second program uses those calibration constants to calculate heading, or yaw. The second program uses the offsets and scale parameters for MY PARTICULAR SENSOR. These values were determined using the first program. You must determine these values for your sensor, and then edit the second program to use your particular calibration parameters.

Program to determine your calibration parameters:

#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
#include <Wire.h>
#include <QMC5883LCompass.h>
int x, y, z;
int xMax = -10000;
int xMin = 10000;
int yMax = -10000;
int yMin = 10000;
int zMax = -10000;
int zMin = 10000;
float xOffset, xScale, yOffset, yScale, zOffset, zScale;
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();
  if (x > xMax) {
    xMax = x;
  }
  if (x < xMin) {
    xMin = x;
  }
  if (y>yMax){
    yMax=y;
  }
  if (y<yMin){
    yMin=y;
  }
  if (z > zMax) {
    zMax = z;
  }
  if (z < zMin) {
    zMin = z;
  }
  xOffset = (xMax + xMin) / 2.;
  yOffset = (yMax + yMin) / 2.;
  zOffset = (zMax + zMin) / 2.;
  xScale = 2. / (xMax - xMin);
  yScale = 2. / (yMax - yMin);
  zScale = 2. / (zMax - zMin);
  Serial.print(x);
  Serial.print(',');
  Serial.print(y);
  Serial.print(',');
  Serial.print(z);
    Serial.print(',');
  Serial.print(xMax);
  Serial.print(',');
  Serial.print(xMin);
  Serial.print(',');
  Serial.print(yMax);
  Serial.print(',');
  Serial.print(yMin);
  Serial.print(',');
  Serial.print(zMax);
  Serial.print(',');
  Serial.print(zMin);
  Serial.print(',');
  Serial.print(xOffset);
  Serial.print(',');
  Serial.print(yOffset);
  Serial.print(',');
  Serial.print(zOffset);
  Serial.print(',');
  Serial.print(xScale,5);
  Serial.print(',');
  Serial.print(yScale,5);
  Serial.print(',');
  Serial.println(zScale,5);
  delay(100);
}

#include <Adafruit_MPU6050.h>

#include <Adafruit_Sensor.h>

#include <Wire.h>

#include <QMC5883LCompass.h>

int x, y, z;

int xMax = -10000;

int xMin = 10000;

int yMax = -10000;

int yMin = 10000;

int zMax = -10000;

int zMin = 10000;

float xOffset, xScale, yOffset, yScale, zOffset, zScale;

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();

if (x > xMax) {

xMax = x;

}

if (x < xMin) {

xMin = x;

}

if (y>yMax){

yMax=y;

}

if (y<yMin){

yMin=y;

}

if (z > zMax) {

zMax = z;

}

if (z < zMin) {

zMin = z;

}

xOffset = (xMax + xMin) / 2.;

yOffset = (yMax + yMin) / 2.;

zOffset = (zMax + zMin) / 2.;

xScale = 2. / (xMax - xMin);

yScale = 2. / (yMax - yMin);

zScale = 2. / (zMax - zMin);

Serial.print(x);

Serial.print(',');

Serial.print(y);

Serial.print(',');

Serial.print(z);

Serial.print(',');

Serial.print(xMax);

Serial.print(',');

Serial.print(xMin);

Serial.print(',');

Serial.print(yMax);

Serial.print(',');

Serial.print(yMin);

Serial.print(',');

Serial.print(zMax);

Serial.print(',');

Serial.print(zMin);

Serial.print(',');

Serial.print(xOffset);

Serial.print(',');

Serial.print(yOffset);

Serial.print(',');

Serial.print(zOffset);

Serial.print(',');

Serial.print(xScale,5);

Serial.print(',');

Serial.print(yScale,5);

Serial.print(',');

Serial.println(zScale,5);

delay(100);

}

Once you get your calibration parameters, then put them into this program. This program will then calculate your compass heading:

#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
#include <Wire.h>
#include <QMC5883LCompass.h>
float x,y,z;
//The following numbers are for my particular sensor. You need
//to edit the following lines to put in your sensor calibration
//numbers
float xOffset=-382.5;
float yOffset=378.5;
float zOffset=1014.5;
float xScale = .00121;
float yScale=.00115;
float zScale=.00105;
float head;

Adafruit_MPU6050 mpu;
QMC5883LCompass compass;
void setup() {
Serial.begin(115200);
mpu.begin();
mpu.setI2CBypass(true);
compass.init();
}
void loop() {
 compass.read();
 x = (compass.getX()-xOffset)*xScale;
 y = (compass.getY()-yOffset)*yScale;
 z = (compass.getZ()-zOffset)*zScale;

// Serial.print(x);
// Serial.print(',');
// Serial.print(y);
// Serial.print(',');
// Serial.println(z);
head = atan2(y,x)*360/2/PI;
Serial.print("Heading: ");
Serial.println(head);
 delay(100);
}

#include <Adafruit_MPU6050.h>

#include <Adafruit_Sensor.h>

#include <Wire.h>

#include <QMC5883LCompass.h>

float x,y,z;

//The following numbers are for my particular sensor. You need

//to edit the following lines to put in your sensor calibration

//numbers

float xOffset=-382.5;

float yOffset=378.5;

float zOffset=1014.5;

float xScale = .00121;

float yScale=.00115;

float zScale=.00105;

float head;

Adafruit_MPU6050 mpu;

QMC5883LCompass compass;

void setup() {

Serial.begin(115200);

mpu.begin();

mpu.setI2CBypass(true);

compass.init();

}

void loop() {

compass.read();

x = (compass.getX()-xOffset)*xScale;

y = (compass.getY()-yOffset)*yScale;

z = (compass.getZ()-zOffset)*zScale;

// Serial.print(x);

// Serial.print(',');

// Serial.print(y);

// Serial.print(',');

// Serial.println(z);

head = atan2(y,x)*360/2/PI;

Serial.print("Heading: ");

Serial.println(head);

delay(100);

}

Arduino

Using the QMC5883L Magnetometers on the GY-87 Module

September 17, 2025 admin

In this video lesson we activate the QMC5883L 3-axis magnetometer on our GY-87 module. We show how to read the raw magnetic field strength in the x, y, and z axis. Your homework assignment will be to then calibrate the measurements such that you center the measured values around 0, and create a unit circle. This calibration will be very similar to what we did for the accelerometers a few weeks ago. This is the schematic we continue to use in this lesson:

This is the code we developed in todays lesson to read the raw data from the magnetometers.

#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);

}

Technology Tutorials

Category Archives: Arduino

Improving Digital Compass Accuracy With a Low Pass Filter

Calibrated Compass Display in Python and PyQt5

Plotting X-Y-Z Magnetometer Data for Accurate Calibration

Calibrating a 3-Axis Magnetometer

Using the QMC5883L Magnetometers on the GY-87 Module

Making The World a Better Place One High Tech Project at a Time. Enjoy!