All posts by admin

Below we show you an example KML file that allows you too display your logged GPS data on Google Earth. For simplicity, we have included two GPS points. First, notice that the ordered pairs are Longitude,Latitude. Notice this is reversed of what we would normally expect, but it is important to note the order . . . Longitude must be put as the first term in the ordered pair. Also notice that the ordered pair of data show up two times in the file. The first is to create the dot, or placemark on the map, and the second list creates the line over your logged path. Now, the challenge for you is to write a python program that takes your log.txt file, which contains simple comma delimited data, lat,lon, and use that to generate a .kml file as shown below.

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
  <Document>
    <name>Path from Pico</name>
    <Style id="pointStyle">
      <IconStyle>
        <Icon><href>http://maps.google.com/mapfiles/kml/shapes/placemark_circle.png</href></Icon>
        <scale>1.0</scale>
      </IconStyle>
    </Style>
    <Style id="lineStyle">
      <LineStyle><color>ff0000ff</color><width>3</width></LineStyle>
    </Style>
    <Placemark>
      <styleUrl>#pointStyle</styleUrl>
      <MultiGeometry>
<Point><coordinates>
33.16453,0.47860332
</coordinates></Point>
<Point><coordinates>
33.164512,0.478673336
</coordinates></Point>
</MultiGeometry>
    </Placemark>
    <Placemark>
      <name>Path</name>
      <styleUrl>#lineStyle</styleUrl>
      <LineString>
        <tessellate>1</tessellate>
        <altitudeMode>clampToGround</altitudeMode>
        <coordinates>
33.16453,0.47860332 
33.164512,0.478673336 
</coordinates>
      </LineString>
    </Placemark>
  </Document>
</kml>

<?xml version="1.0" encoding="UTF-8"?>

<Icon><href>http://maps.google.com/mapfiles/kml/shapes/placemark_circle.png</href></Icon>

</IconStyle>

</Style>

</Style>

<styleUrl>#pointStyle</styleUrl>

33.16453,0.47860332

</coordinates></Point>

33.164512,0.478673336

</coordinates></Point>

</MultiGeometry>

</Placemark>

<styleUrl>#lineStyle</styleUrl>

<altitudeMode>clampToGround</altitudeMode>

33.16453,0.47860332

33.164512,0.478673336

</coordinates>

</LineString>

</Placemark>

</Document>

</kml>

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:

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

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()

Python, Raspberry Pi Pico

Logging GPS Data on Your Raspberry Pi Pico W GPS Tracker Project

October 1, 2025 admin

In this lesson I show you how to log GPS data to the flash memory on your Raspberry Pi Pico W. This allows you to not only know where you are, but to also know where you have been. In this lesson, this is the schematic of your project circuit.

Schematic for Controlling GPS Tracker from the Breadvolt

For your convenience, here is the code we developed in the the video:

from machine import Pin,I2C,UART
import time
import _thread
from ssd1306 import SSD1306_I2C
import math

with open('log.txt','w') as file:
    pass
utcCorrect = 3
earthRadius = 6371000
i2c2 = I2C(1, sda=Pin(2), scl=Pin(3), freq=400000)
dsp = SSD1306_I2C(128,64,i2c2)

sysState = 0

dataLock = _thread.allocate_lock()
keepRunning = True
GPS = UART(1, baudrate=9600, tx=machine.Pin(8), rx=machine.Pin(9))
# Reset GPS
GPS.write(b'$PMTK314,-1*04\r\n')
#The following line ensures that the GPS reports the GPVTG NMEA Sentence
GPS.write(b"$PMTK314,0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0*28\r\n")
NMEAdata = {
    'GPGGA' : "",
    'GPGSA' : "",
    'GPRMC' : "",
    'GPVTG' : ""
    }
GPSdata = {
    'latDD' 	: 0,
    'lonDD'		: 0,
    'heading'	: 0,
    'fix'		: False,
    'sats'		: 0,
    'knots'		: 0,
    'time'		: '00:00:00',
    'date'		: '00/00/0000',
    'alt'		: 0.0
    }
def calculateDistance(lat1,lon1,lat2,lon2):
    lat1=lat1*2*math.pi/360
    lon1=lon1*2*math.pi/360
    lat2=lat2*2*math.pi/360
    lon2=lon2*2*math.pi/360
    theta = 2*math.asin(math.sqrt(
        math.sin((lat2-lat1)/2)**2 +
        math.cos(lat1)*math.cos(lat2)*math.sin((lon2-lon1)/2)**2
        ))
    distance = earthRadius * theta
    return distance
def calculateHeading(lat1,lon1,lat2,lon2):
    lat1=lat1*2*math.pi/360
    lon1=lon1*2*math.pi/360
    lat2=lat2*2*math.pi/360
    lon2=lon2*2*math.pi/360
    deltaLon=lon2-lon1
    xC=math.sin(deltaLon)*math.cos(lat2)
    yC=math.cos(lat1)*math.sin(lat2)-math.sin(lat1)*math.cos(lat2)*math.cos(deltaLon)
    beta = math.atan2(xC,yC)
    betaDeg = beta*360/2/math.pi
    return betaDeg
def gpsThread():
    print("Thread Running")
    global keepRunning,NMEAdata
    GPGGA = ""
    GPGSA = ""
    GPRMC = ""
    GPVTG = ""
    while not GPS.any():
        pass
    while GPS.any():
        junk = GPS.read()
        print(junk)
    myNMEA = ""
    while keepRunning:
        if GPS.any():
            myChar=GPS.read(1).decode('utf-8')
            myNMEA = myNMEA + myChar
            if myChar == '\n':
                myNMEA = myNMEA.strip()
                if myNMEA[1:6] == "GPGGA":
                    GPGGA = myNMEA
                if myNMEA[1:6] == "GPGSA":
                    GPGSA = myNMEA
                if myNMEA[1:6] == "GPRMC":
                    GPRMC = myNMEA
                if myNMEA[1:6] == "GPVTG":
                    GPVTG = myNMEA
                if GPGGA != "" and GPGSA!="" and GPRMC!="" and GPVTG!="":
                    dataLock.acquire()
                    NMEAdata = {
                        'GPGGA' : GPGGA,
                        'GPGSA' : GPGSA,
                        'GPRMC' : GPRMC,
                        'GPVTG' : GPVTG
                        }
                    dataLock.release()
                myNMEA = ""
    print("Thread Terminated Cleanly")
def parseGPS():
    readFix=int(NMEAmain['GPGGA'].split(',')[6])
    if readFix !=0:
        GPSdata['fix'] = True
        latRAW = NMEAmain['GPGGA'].split(',')[2]
        latDD = int(latRAW[0:2]) + float(latRAW[2:])/60
        if NMEAmain['GPGGA'].split(',')[3] == 'S':
            latDD = -latDD
        GPSdata['latDD']= latDD
        lonRAW=NMEAmain['GPGGA'].split(',')[4]
        lonDD=int(lonRAW[0:3]) + float(lonRAW[3:])/60
        if NMEAmain['GPGGA'].split(',')[5] == 'W':
            lonDD = -lonDD
        GPSdata['lonDD'] = lonDD
        heading = float(NMEAmain['GPRMC'].split(',')[8])
        GPSdata['heading'] = heading
        knots = float(NMEAmain['GPRMC'].split(',')[7])
        GPSdata['knots'] = knots
        sats = int(NMEAmain['GPGGA'].split(',')[7])
        GPSdata['sats'] = sats
        utcTime = NMEAmain['GPGGA'].split(',')[1]
        utcDate = NMEAmain['GPRMC'].split(',')[9]
        # utcTime = "013445.000"
        # utcDate = "010125"

        # Extract year from UTC date (format: DDMMYY), prepend '20' for full year (e.g., '25' → '2025')
        myYear = '20' + utcDate[4:]
        # Extract month from UTC date (e.g., '01' for January)
        myMonth = utcDate[2:4]
        # Extract day from UTC date (e.g., '01' for 1st)
        myDay = utcDate[0:2]
        # Calculate hours by adding UTC offset to UTC hours, convert to string
        myHours = str(int(utcTime[0:2]) + utcCorrect)
        # Extract minutes from UTC time (e.g., '34' from '013445.000')
        myMin = utcTime[2:4]
        # Extract seconds from UTC time (e.g., '45' from '013445.000')
        mySec = utcTime[4:6]

        # Define array of maximum days per month (index 0-11 for months 1-12: Jan to Dec)
        maxDays = ['31', '28', '31', '30', '31', '30', '31', '31', '30', '31', '30', '31']

        # Check if year is a leap year (simplified: divisible by 4); if so, set February to 29 days
        if int(myYear) % 4 == 0:
            maxDays[1] = '29'

        # Check if hours exceed 24 (for positive UTC offsets, e.g., UTC 22:00 + 5 = 27:00)
        if int(myHours) >= 24:
            # Subtract 24 from hours to wrap around to next day (e.g., 27 → 3)
            myHours = str(int(myHours) - 24)
            # Pad hours with leading zero if single digit (e.g., '3' → '03')
            if len(myHours) < 2:
                myHours = '0' + myHours
            # Increment day to account for crossing midnight (e.g., 30 → 31)
            myDay = str(int(myDay) + 1)
            # Check if day exceeds maximum days for the current month (e.g., June 31 > 30)
            if int(myDay) > int(maxDays[int(myMonth) - 1]):
                # Reset day to 1 for the next month
                myDay = '01'
                # Increment month (e.g., June → July)
                myMonth = str(int(myMonth) + 1)
                # Check if month exceeds 12 (e.g., December → January)
                if int(myMonth) > 12:
                    # Reset month to January
                    myMonth = '01'
                    # Increment year (e.g., 2025 → 2026)
                    myYear = str(int(myYear) + 1)
            # Pad day with leading zero if single digit (e.g., '1' → '01')
            if len(myDay) < 2:
                myDay = '0' + myDay
            # Pad month with leading zero if single digit (e.g., '7' → '07')
            if len(myMonth) < 2:
                myMonth = '0' + myMonth

        # Check if hours are negative (for negative UTC offsets, e.g., UTC 01:00 - 5 = -4)
        if int(myHours) < 0:
            # Add 24 to hours to wrap around to previous day (e.g., -4 → 20)
            myHours = str(int(myHours) + 24)
            # Pad hours with leading zero if single digit (e.g., '3' → '03')
            if len(myHours) < 2:
                myHours = '0' + myHours
            # Decrement day to account for crossing midnight backward (e.g., 01 → 00)
            myDay = str(int(myDay) - 1)
            # Check if day is less than 1 (e.g., January 1 → December 31)
            if int(myDay) < 1:
                # Decrement month (e.g., January → December)
                myMonth = str(int(myMonth) - 1)
                # Check if month is less than 1 (e.g., January → December of previous year)
                if int(myMonth) < 1:
                    # Set month to December
                    myMonth = '12'
                    # Decrement year (e.g., 2025 → 2024)
                    myYear = str(int(myYear) - 1)
                # Set day to maximum days of the new month (e.g., December → 31)
                myDay = maxDays[int(myMonth) - 1]
            # Pad day with leading zero if single digit (e.g., '1' → '01')
            if len(myDay) < 2:
                myDay = '0' + myDay
            # Pad month with leading zero if single digit (e.g., '7' → '07')
            if len(myMonth) < 2:
                myMonth = '0' + myMonth

        # Combine hours, minutes, seconds into time string (e.g., '20:34:45')
        myTime = myHours + ':' + myMin + ':' + mySec
        # Combine month, day, year into date string (e.g., '12/31/2024')
        myDate = myMonth + '/' + myDay + '/' + myYear
        # Store local time in GPSdata dictionary
        GPSdata['time'] = myTime
        # Store local date in GPSdata dictionary
        GPSdata['date'] = myDate
        GPSdata['alt'] = float(NMEAmain['GPGGA'].split(',')[9])
def dispOLED():
    global sysState,latitude1,longitude1,latitude2,longitude2
    dsp.fill(0)
    if GPSdata['fix'] == False:
        dsp.text("Waiting for Fix . . .",0,0)
    if GPSdata['fix'] == True:
        if sysState%3== 0:
            dsp.fill(0)
            dsp.text("Ultimate GPS",0,0)
            dsp.text(GPSdata['date'][0:5] + ' '+GPSdata['time'],0,16)
            dsp.text("LAT: "+str(GPSdata['latDD']),0,26)
            dsp.text("LON: "+str(GPSdata['lonDD']),0,36)
            dsp.text("SATS: "+str(GPSdata['sats']),0,46)
            dsp.text("Press Btn LOG",0,56)
        if sysState%3==1:
            lat=str(GPSdata['latDD'])
            lon=str(GPSdata['lonDD'])
            latLon = lat+','+lon+'\n'
            try:
                with open('log.txt', 'a') as file:
                    file.write(latLon)
                    file.flush()
                time.sleep(.1)
            except Exception as e:
                print("File Write Error:", e)
            dsp.fill(0)
            dsp.text("LOGGING DATA",0,0)
            dsp.text(GPSdata['date'][0:5] + ' '+GPSdata['time'],0,16)
            dsp.text("LAT: "+lat,0,26)
            dsp.text("LON: "+lon,0,36)
            dsp.text("Btn Stop Logging",0,56)
        if sysState%3==2:
            dsp.fill(0)
            dsp.text("Logging Stopped",0,0)
            dsp.text(GPSdata['date'][0:5] + ' '+GPSdata['time'],0,16)
            dsp.text("LAT: "+str(GPSdata['latDD']),0,26)
            dsp.text("LON: "+str(GPSdata['lonDD']),0,36)
            dsp.show()
            time.sleep(2)
            sysState=0
 
    dsp.show()
butOnePin = 12
butOne = Pin(butOnePin, Pin.IN, Pin.PULL_UP)
butOneUp = 0
butOneDown = 0
butOneOld = 1

def butOneIRQ(pin):
    global butOneUp,butOneDown,butOneOld,sysState
    butOneValue = butOne.value()
    if butOneValue==0:
        butOneDown=time.ticks_ms()
    if butOneValue==1:
        butOneUp = time.ticks_ms()
    if butOneOld==1 and butOneValue==0 and butOneDown-butOneUp>50:
        sysState = sysState + 1
        print('Button One Triggered')
    butOneOld=butOneValue
    
butOne.irq(trigger=Pin.IRQ_FALLING | Pin.IRQ_RISING , handler = butOneIRQ)
 
_thread.start_new_thread(gpsThread,())
time.sleep(3)
try:
    while True:
        dataLock.acquire()
        NMEAmain = NMEAdata.copy()
        dataLock.release()
        parseGPS()
        if GPSdata['fix'] == False:
            print("Waiting for Fix . . .")
        if GPSdata['fix'] == True:
            print("Ultimate GPS Tracker Report: ")
            print(GPSdata['time'],GPSdata['date'])
            print("Lat and Lon: ",GPSdata['latDD'],GPSdata['lonDD'])
            print("Knots: ",GPSdata['knots'])
            print("Heading: ",GPSdata['heading'])
            print("Elevation: ",GPSdata['alt'])
            print("Sats: ",GPSdata['sats'])
            print()
        dispOLED()
        time.sleep(1)


except KeyboardInterrupt:
    print("\nStopping Program . . . Cleaning Up UART")
    keepRunning = False
    time.sleep(1)
    GPS.deinit()
    time.sleep(1)
    dsp.fill(0)
    dsp.show()
    print("Exited Cleanly")

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from machine import Pin,I2C,UART

import time

import _thread

from ssd1306 import SSD1306_I2C

import math

with open('log.txt','w') as file:

pass

utcCorrect = 3

earthRadius = 6371000

i2c2 = I2C(1, sda=Pin(2), scl=Pin(3), freq=400000)

dsp = SSD1306_I2C(128,64,i2c2)

sysState = 0

dataLock = _thread.allocate_lock()

keepRunning = True

GPS = UART(1, baudrate=9600, tx=machine.Pin(8), rx=machine.Pin(9))

# Reset GPS

GPS.write(b'$PMTK314,-1*04\r\n')

#The following line ensures that the GPS reports the GPVTG NMEA Sentence

GPS.write(b"$PMTK314,0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0*28\r\n")

NMEAdata = {

'GPGGA' : "",

'GPGSA' : "",

'GPRMC' : "",

'GPVTG' : ""

}

GPSdata = {

'latDD' : 0,

'lonDD' : 0,

'heading' : 0,

'fix' : False,

'sats' : 0,

'knots' : 0,

'time' : '00:00:00',

'date' : '00/00/0000',

'alt' : 0.0

}

def calculateDistance(lat1,lon1,lat2,lon2):

lat1=lat1*2*math.pi/360

lon1=lon1*2*math.pi/360

lat2=lat2*2*math.pi/360

lon2=lon2*2*math.pi/360

theta = 2*math.asin(math.sqrt(

math.sin((lat2-lat1)/2)**2 +

math.cos(lat1)*math.cos(lat2)*math.sin((lon2-lon1)/2)**2

))

distance = earthRadius * theta

return distance

def calculateHeading(lat1,lon1,lat2,lon2):

lat1=lat1*2*math.pi/360

lon1=lon1*2*math.pi/360

lat2=lat2*2*math.pi/360

lon2=lon2*2*math.pi/360

deltaLon=lon2-lon1

xC=math.sin(deltaLon)*math.cos(lat2)

yC=math.cos(lat1)*math.sin(lat2)-math.sin(lat1)*math.cos(lat2)*math.cos(deltaLon)

beta = math.atan2(xC,yC)

betaDeg = beta*360/2/math.pi

return betaDeg

def gpsThread():

print("Thread Running")

global keepRunning,NMEAdata

GPGGA = ""

GPGSA = ""

GPRMC = ""

GPVTG = ""

while not GPS.any():

pass

while GPS.any():

junk = GPS.read()

print(junk)

myNMEA = ""

while keepRunning:

if GPS.any():

myChar=GPS.read(1).decode('utf-8')

myNMEA = myNMEA + myChar

if myChar == '\n':

myNMEA = myNMEA.strip()

if myNMEA[1:6] == "GPGGA":

GPGGA = myNMEA

if myNMEA[1:6] == "GPGSA":

GPGSA = myNMEA

if myNMEA[1:6] == "GPRMC":

GPRMC = myNMEA

if myNMEA[1:6] == "GPVTG":

GPVTG = myNMEA

if GPGGA != "" and GPGSA!="" and GPRMC!="" and GPVTG!="":

dataLock.acquire()

NMEAdata = {

'GPGGA' : GPGGA,

'GPGSA' : GPGSA,

'GPRMC' : GPRMC,

'GPVTG' : GPVTG

}

dataLock.release()

myNMEA = ""

print("Thread Terminated Cleanly")

def parseGPS():

readFix=int(NMEAmain['GPGGA'].split(',')[6])

if readFix !=0:

GPSdata['fix'] = True

latRAW = NMEAmain['GPGGA'].split(',')[2]

latDD = int(latRAW[0:2]) + float(latRAW[2:])/60

if NMEAmain['GPGGA'].split(',')[3] == 'S':

latDD = -latDD

GPSdata['latDD']= latDD

lonRAW=NMEAmain['GPGGA'].split(',')[4]

lonDD=int(lonRAW[0:3]) + float(lonRAW[3:])/60

if NMEAmain['GPGGA'].split(',')[5] == 'W':

lonDD = -lonDD

GPSdata['lonDD'] = lonDD

heading = float(NMEAmain['GPRMC'].split(',')[8])

GPSdata['heading'] = heading

knots = float(NMEAmain['GPRMC'].split(',')[7])

GPSdata['knots'] = knots

sats = int(NMEAmain['GPGGA'].split(',')[7])

GPSdata['sats'] = sats

utcTime = NMEAmain['GPGGA'].split(',')[1]

utcDate = NMEAmain['GPRMC'].split(',')[9]

# utcTime = "013445.000"

# utcDate = "010125"

# Extract year from UTC date (format: DDMMYY), prepend '20' for full year (e.g., '25' → '2025')

myYear = '20' + utcDate[4:]

# Extract month from UTC date (e.g., '01' for January)

myMonth = utcDate[2:4]

# Extract day from UTC date (e.g., '01' for 1st)

myDay = utcDate[0:2]

# Calculate hours by adding UTC offset to UTC hours, convert to string

myHours = str(int(utcTime[0:2]) + utcCorrect)

# Extract minutes from UTC time (e.g., '34' from '013445.000')

myMin = utcTime[2:4]

# Extract seconds from UTC time (e.g., '45' from '013445.000')

mySec = utcTime[4:6]

# Define array of maximum days per month (index 0-11 for months 1-12: Jan to Dec)

maxDays = ['31', '28', '31', '30', '31', '30', '31', '31', '30', '31', '30', '31']

# Check if year is a leap year (simplified: divisible by 4); if so, set February to 29 days

if int(myYear) % 4 == 0:

maxDays[1] = '29'

# Check if hours exceed 24 (for positive UTC offsets, e.g., UTC 22:00 + 5 = 27:00)

if int(myHours) >= 24:

# Subtract 24 from hours to wrap around to next day (e.g., 27 → 3)

myHours = str(int(myHours) - 24)

# Pad hours with leading zero if single digit (e.g., '3' → '03')

if len(myHours) < 2:

myHours = '0' + myHours

# Increment day to account for crossing midnight (e.g., 30 → 31)

myDay = str(int(myDay) + 1)

# Check if day exceeds maximum days for the current month (e.g., June 31 > 30)

if int(myDay) > int(maxDays[int(myMonth) - 1]):

# Reset day to 1 for the next month

myDay = '01'

# Increment month (e.g., June → July)

myMonth = str(int(myMonth) + 1)

# Check if month exceeds 12 (e.g., December → January)

if int(myMonth) > 12:

# Reset month to January

myMonth = '01'

# Increment year (e.g., 2025 → 2026)

myYear = str(int(myYear) + 1)

# Pad day with leading zero if single digit (e.g., '1' → '01')

if len(myDay) < 2:

myDay = '0' + myDay

# Pad month with leading zero if single digit (e.g., '7' → '07')

if len(myMonth) < 2:

myMonth = '0' + myMonth

# Check if hours are negative (for negative UTC offsets, e.g., UTC 01:00 - 5 = -4)

if int(myHours) < 0:

# Add 24 to hours to wrap around to previous day (e.g., -4 → 20)

myHours = str(int(myHours) + 24)

# Pad hours with leading zero if single digit (e.g., '3' → '03')

if len(myHours) < 2:

myHours = '0' + myHours

# Decrement day to account for crossing midnight backward (e.g., 01 → 00)

myDay = str(int(myDay) - 1)

# Check if day is less than 1 (e.g., January 1 → December 31)

if int(myDay) < 1:

# Decrement month (e.g., January → December)

myMonth = str(int(myMonth) - 1)

# Check if month is less than 1 (e.g., January → December of previous year)

if int(myMonth) < 1:

# Set month to December

myMonth = '12'

# Decrement year (e.g., 2025 → 2024)

myYear = str(int(myYear) - 1)

# Set day to maximum days of the new month (e.g., December → 31)

myDay = maxDays[int(myMonth) - 1]

# Pad day with leading zero if single digit (e.g., '1' → '01')

if len(myDay) < 2:

myDay = '0' + myDay

# Pad month with leading zero if single digit (e.g., '7' → '07')

if len(myMonth) < 2:

myMonth = '0' + myMonth

# Combine hours, minutes, seconds into time string (e.g., '20:34:45')

myTime = myHours + ':' + myMin + ':' + mySec

# Combine month, day, year into date string (e.g., '12/31/2024')

myDate = myMonth + '/' + myDay + '/' + myYear

# Store local time in GPSdata dictionary

GPSdata['time'] = myTime

# Store local date in GPSdata dictionary

GPSdata['date'] = myDate

GPSdata['alt'] = float(NMEAmain['GPGGA'].split(',')[9])

def dispOLED():

global sysState,latitude1,longitude1,latitude2,longitude2

dsp.fill(0)

if GPSdata['fix'] == False:

dsp.text("Waiting for Fix . . .",0,0)

if GPSdata['fix'] == True:

if sysState%3== 0:

dsp.fill(0)

dsp.text("Ultimate GPS",0,0)

dsp.text(GPSdata['date'][0:5] + ' '+GPSdata['time'],0,16)

dsp.text("LAT: "+str(GPSdata['latDD']),0,26)

dsp.text("LON: "+str(GPSdata['lonDD']),0,36)

dsp.text("SATS: "+str(GPSdata['sats']),0,46)

dsp.text("Press Btn LOG",0,56)

if sysState%3==1:

lat=str(GPSdata['latDD'])

lon=str(GPSdata['lonDD'])

latLon = lat+','+lon+'\n'

try:

with open('log.txt', 'a') as file:

file.write(latLon)

file.flush()

time.sleep(.1)

except Exception as e:

print("File Write Error:", e)

dsp.fill(0)

dsp.text("LOGGING DATA",0,0)

dsp.text(GPSdata['date'][0:5] + ' '+GPSdata['time'],0,16)

dsp.text("LAT: "+lat,0,26)

dsp.text("LON: "+lon,0,36)

dsp.text("Btn Stop Logging",0,56)

if sysState%3==2:

dsp.fill(0)

dsp.text("Logging Stopped",0,0)

dsp.text(GPSdata['date'][0:5] + ' '+GPSdata['time'],0,16)

dsp.text("LAT: "+str(GPSdata['latDD']),0,26)

dsp.text("LON: "+str(GPSdata['lonDD']),0,36)

dsp.show()

time.sleep(2)

sysState=0

dsp.show()

butOnePin = 12

butOne = Pin(butOnePin, Pin.IN, Pin.PULL_UP)

butOneUp = 0

butOneDown = 0

butOneOld = 1

def butOneIRQ(pin):

global butOneUp,butOneDown,butOneOld,sysState

butOneValue = butOne.value()

if butOneValue==0:

butOneDown=time.ticks_ms()

if butOneValue==1:

butOneUp = time.ticks_ms()

if butOneOld==1 and butOneValue==0 and butOneDown-butOneUp>50:

sysState = sysState + 1

print('Button One Triggered')

butOneOld=butOneValue

butOne.irq(trigger=Pin.IRQ_FALLING | Pin.IRQ_RISING , handler = butOneIRQ)

_thread.start_new_thread(gpsThread,())

time.sleep(3)

try:

while True:

dataLock.acquire()

NMEAmain = NMEAdata.copy()

dataLock.release()

parseGPS()

if GPSdata['fix'] == False:

print("Waiting for Fix . . .")

if GPSdata['fix'] == True:

print("Ultimate GPS Tracker Report: ")

print(GPSdata['time'],GPSdata['date'])

print("Lat and Lon: ",GPSdata['latDD'],GPSdata['lonDD'])

print("Knots: ",GPSdata['knots'])

print("Heading: ",GPSdata['heading'])

print("Elevation: ",GPSdata['alt'])

print("Sats: ",GPSdata['sats'])

print()

dispOLED()

time.sleep(1)

except KeyboardInterrupt:

print("\nStopping Program . . . Cleaning Up UART")

keepRunning = False

time.sleep(1)

GPS.deinit()

time.sleep(1)

dsp.fill(0)

dsp.show()

print("Exited Cleanly")

MicroPython, Raspberry Pi Pico

Transfer Data Log Files from the Raspberry Pi Pico W to Your Desktop PC

September 23, 2025 admin

Many Raspberry Pi Pico W project in microPython require the logging of sensor data. With these log files, we need a convenient way to transfer the data from the Pi Pico to a desktop PC. In earlier lessons, we showed how to log data to the Pi Pico flash memory. In today’s lesson we show how to transfer those log files to your PC. This is the code we developed in the video lesson.

import serial
import time
serialPort= 'COM7'
baudRate = 115200
ser = serial.Serial(serialPort,baudRate, timeout=5)
time.sleep(1)
ser.write(b"f=open('log.txt','r')\r\n")
line =ser.readline().decode('utf-8').strip()
print(line)
time.sleep(.1)
with open('log.txt','w') as file:
    while line !="''":
        ser.write(b"f.readline()\r\n")
        line =ser.readline().decode('utf-8').strip()
        print("LINE: ",line)
        line =ser.readline().decode('utf-8').strip()
        print("LINE: ",line)
        if line.startswith("'") and line !="''":
            line = line[1:-3]
            file.write(line+'\n')
ser.write(b"f.close()\r\n")
ser.close()

import serial

import time

serialPort= 'COM7'

baudRate = 115200

ser = serial.Serial(serialPort,baudRate, timeout=5)

time.sleep(1)

ser.write(b"f=open('log.txt','r')\r\n")

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

print(line)

time.sleep(.1)

with open('log.txt','w') as file:

while line !="''":

ser.write(b"f.readline()\r\n")

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

print("LINE: ",line)

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

print("LINE: ",line)

if line.startswith("'") and line !="''":

line = line[1:-3]

file.write(line+'\n')

ser.write(b"f.close()\r\n")

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);

}

Technology Tutorials

All posts by admin

Create a KML File to Display your GPS Data on Google Earth

Plotting X-Y-Z Magnetometer Data for Accurate Calibration

Logging GPS Data on Your Raspberry Pi Pico W GPS Tracker Project

Transfer Data Log Files from the Raspberry Pi Pico W to Your Desktop PC

Calibrating a 3-Axis Magnetometer

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