pytrack gps decoder

gpsdecoder.py

class GPSDecoder:
    def __init__(self, i2c=None):
        if i2c is None:
            from machine import I2C
            i2c = I2C(0, mode=I2C.MASTER, pins=('G9', 'G8'))
        self.i2c = i2c
        self.buf = ""
        self.clear()
    def clear(self):
        self.fixStatus = self.lat = self.lng = self.utcTime = None
        self.pdop = self.hdop = self.vdop = None
        self.alt = self.geoid = None
        self.cogT = self.cogM = self.speedKnots = self.speedKm = None
        self.utcDate = None
    def to_decimal(self, pos, mod):
        import math

        dotoffset = pos.find('.')

        if 4 == dotoffset:
            d, m = (pos[0:2], pos[2:])
        elif 5 == dotoffset:
            d, m = (pos[0:3], pos[3:])

        d = float(d)
        m = float(m)

        r = m / 60.0

        result = (d + r)

        if -1 != "SW".rfind(mod):
            result *= -1.0

        return result
    def hasPosition(self):
        result = None != self.fixStatus

        result &= None != self.lat
        result &= None != self.lng
        result &= None != self.utcTime
        result &= None != self.pdop
        result &= None != self.hdop
        result &= None != self.vdop
        result &= None != self.alt
        result &= None != self.geoid
        result &= None != self.fixStatus
        result &= None != self.utcDate
        #result &= None != self.cogT
        #result &= None != self.cogM
        #result &= None != self.speedKnots
        #result &= None != self.speedKm

        return result
    def parse(self):
        from utime import sleep_ms
        from math import modf

        received = self.i2c.readfrom(0x10, 255)

        self.buf += received.decode("utf8")
        lines = self.buf.split("\n")
        off = 0
        for line in lines:
            # if len(line) > 2:
            #     print("line trailer: %s" % hexlify(line[-2:]))
            off += len(line) + 2

            exclude = False
            if not line:
                exclude = True
            elif len(line) <= 1:
                exclude = True
            elif '$' != line[0]:
                exclude = True
            elif line[-1:] != "\r":
                exclude = True

            if exclude:
                self.buf = self.buf[off:]
                continue

            if len(self.buf) > 1024:
                self.buf = self.buf[1+self.buf.rfind("\n"):]

            line = line.strip()

            lastAsterisk = line.rfind('*')

            if -1 != lastAsterisk:
                line = line[:lastAsterisk]

            args = line.split(",")

            command = args[0]

            if command[-3:] == "GLL":
                lat = args[1]
                ns = args[2]
                lng = args[3]
                ew = args[4]
                utcTime = args[5]
                dataValid = args[6]
                positioningMode = args[7]

                self.lat = self.to_decimal(lat, ns)

                self.lng = self.to_decimal(lng, ew)

                self.utcTime = utcTime
            elif command[-3:] == "GSA":
                self.fixStatus = args[2]

                self.pdop = float(args[-3])
                self.hdop = float(args[-2])
                self.vdop = float(args[-1])
            elif command[-3:] == "GSV":
                # Ignored. Pura Groselha.
                pass
            elif command[-3:] == "GGA":
                self.utcTime = args[1]
                self.lat = self.to_decimal(args[2], args[3])

                self.lng = self.to_decimal(args[4], args[5])

                self.fixStatus = args[6]

                self.hdop = float(args[8])
                self.alt = float(args[9])
                self.geoid = float(args[11])
            elif command[-3:] == "VTG":
                #print("args:%s" % repr(args))
                if 0 != len(args[1]):
                    self.cogT = float(args[1])

                if 0 != len(args[3]):
                    self.cogM = float(args[3])

                self.speedKnots = float(args[5])
                self.speedKm = float(args[7])
                self.fixStatus = args[9][0]
            elif command[-3:] == "RMC":
                valid = args[2]

                if "A" == valid:
                    self.utcTime = args[1]
                    self.lat = self.to_decimal(args[3], args[4])
                    self.lng = self.to_decimal(args[5], args[6])
                    self.speedKnots = float(args[7])
                    self.cogM = float(args[8])
                    self.utcDate = args[9]
                    self.fixStatus = args[12][0]
            else:
                print("Not parsed: %s" % repr(args))

            self.buf = self.buf[off:]
        # TODO: Use just the time difference instead of a fixed value
        sleep_ms(500)

        return self.hasPosition()

d = GPSDecoder()

while not d.parse():
    pass