tk102-nmea.py

def parse( data ):
    """
        @return {ok:<0|1>,ts:<utc_datetime>,coord:[<lon>,<lat>],speed:<km/h>,dir:<bearing>}
        or None on error or not gps ok
    """

    try:
        gp = data.index("GPRMC")
        cp = data.index("*",gp+4)

        i = data.index('imei:', cp)
        imei = data[i+5:data.index(',',i+6)]

        gprmc = data[gp:cp]

        csum = 0
        for c in gprmc:
            csum ^= ord(c)
        if csum != int(data[cp+1:cp+3], 16):
            return None     # bad checksum

        f = gprmc.split(',',10)

        return {
            'imei': imei,
            'ok': [0,1][f[2] == 'A'],
            'ts': datetime.strptime(f[9]+'-'+f[1]+"000","%d%m%y-%H%M%S.%f"),
            'coord': [
                (float(f[5][0:3]) + (float(f[5][3:])/60))*{'E':1,'W':-1}[f[6]],
                (float(f[3][0:2]) + (float(f[3][2:])/60))*{'N':1,'S':-1}[f[4]],
            ],
            'speed': float(f[7])*1.852, # knots to km/h
            'dir': float(f[8]),     # azimuth (deg.)
        }

    except (ValueError, IndexError):
        # wrong format
        pass

    return None
#--