In this video lesson I show you how to parse NMEA sentences using the Raspberry Pi Pico W. In our project our pico is connected to the Adafruit Ultimate GPS V3. For this lesson we are using the following schematic:
For your convenience, I have included the code below developed in the video:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 | from machine import Pin,I2C,UART import time import _thread dataLock = _thread.allocate_lock() keepRunning = True GPS = UART(1, baudrate=9600, tx=machine.Pin(8), rx=machine.Pin(9)) # 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 } 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 = NMEAmain['GPGGA'].split(',')[7] GPSdata['sats'] = sats _thread.start_new_thread(gpsThread,()) time.sleep(2) 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("Lat and Lon: ",GPSdata['latDD'],GPSdata['lonDD']) print("Knots: ",GPSdata['knots']) print("Heading: ",GPSdata['heading']) print("Sats: ",GPSdata['sats']) print() time.sleep(10) except KeyboardInterrupt: print("\nStopping Program . . . Cleaning Up UART") keepRunning = False time.sleep(1) GPS.deinit() time.sleep(1) print("Exited Cleanly") |