Source code for adafruit_gps

# SPDX-FileCopyrightText: 2017 Tony DiCola for Adafruit Industries
# SPDX-FileCopyrightText: 2021 James Carr
#
# SPDX-License-Identifier: MIT

"""
`adafruit_gps`
====================================================

GPS parsing module.  Can parse simple NMEA data sentences from serial GPS
modules to read latitude, longitude, and more.

* Author(s): Tony DiCola, James Carr

Implementation Notes
--------------------

**Hardware:**

* Adafruit `Ultimate GPS Breakout <https://www.adafruit.com/product/746>`_
* Adafruit `Ultimate GPS FeatherWing <https://www.adafruit.com/product/3133>`_

**Software and Dependencies:**

* Adafruit CircuitPython firmware for the ESP8622 and M0-based boards:
  https://github.com/adafruit/circuitpython/releases

"""
import time
from micropython import const

__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_GPS.git"


_GPSI2C_DEFAULT_ADDRESS = const(0x10)

_GLL = 0
_RMC = 1
_GGA = 2
_GSA = 3
_GSA_4_11 = 4
_GSV7 = 5
_GSV11 = 6
_GSV15 = 7
_GSV19 = 8
_RMC_4_1 = 9
_ST_MIN = _GLL
_ST_MAX = _RMC_4_1

_SENTENCE_PARAMS = (
    # 0 - _GLL
    "dcdcfcC",
    # 1 - _RMC
    "fcdcdcffiDCC",
    # 2 - _GGA
    "fdcdciiffsfsIS",
    # 3 - _GSA
    "ciIIIIIIIIIIIIfff",
    # 4 - _GSA_4_11
    "ciIIIIIIIIIIIIfffS",
    # 5 - _GSV7
    "iiiiiiI",
    # 6 - _GSV11
    "iiiiiiIiiiI",
    # 7 - _GSV15
    "iiiiiiIiiiIiiiI",
    # 8 - _GSV19
    "iiiiiiIiiiIiiiIiiiI",
    # 9 - _RMC_4_1
    "fcdcdcffiDCCC",
)


# Internal helper parsing functions.
# These handle input that might be none or null and return none instead of
# throwing errors.
def _parse_degrees(nmea_data):
    # Parse a NMEA lat/long data pair 'dddmm.mmmm' into a pure degrees value.
    # Where ddd is the degrees, mm.mmmm is the minutes.
    if nmea_data is None or len(nmea_data) < 3:
        return None
    raw = float(nmea_data)
    deg = raw // 100
    minutes = raw % 100
    return deg + minutes / 60


def _parse_int(nmea_data):
    if nmea_data is None or nmea_data == "":
        return None
    return int(nmea_data)


def _parse_float(nmea_data):
    if nmea_data is None or nmea_data == "":
        return None
    return float(nmea_data)


def _parse_str(nmea_data):
    if nmea_data is None or nmea_data == "":
        return None
    return str(nmea_data)


def _read_degrees(data, index, neg):
    x = data[index]
    if data[index + 1].lower() == neg:
        x *= -1.0
    return x


def _parse_talker(data_type):
    # Split the data_type into talker and sentence_type
    if data_type[0] == b"P":  # Proprietary codes
        return (data_type[:1], data_type[1:])

    return (data_type[:2], data_type[2:])


def _parse_data(sentence_type, data):
    """Parse sentence data for the specified sentence type and
    return a list of parameters in the correct format, or return None.
    """
    # pylint: disable=too-many-branches

    if not _ST_MIN <= sentence_type <= _ST_MAX:
        # The sentence_type is unknown
        return None

    param_types = _SENTENCE_PARAMS[sentence_type]

    if len(param_types) != len(data):
        # The expected number does not match the number of data items
        return None

    params = []
    try:
        for i, dti in enumerate(data):
            pti = param_types[i]
            len_dti = len(dti)
            nothing = dti is None or len_dti == 0
            if pti == "c":
                # A single character
                if len_dti != 1:
                    return None
                params.append(dti)
            elif pti == "C":
                # A single character or Nothing
                if nothing:
                    params.append(None)
                elif len_dti != 1:
                    return None
                else:
                    params.append(dti)
            elif pti == "d":
                # A number parseable as degrees
                params.append(_parse_degrees(dti))
            elif pti == "D":
                # A number parseable as degrees or Nothing
                if nothing:
                    params.append(None)
                else:
                    params.append(_parse_degrees(dti))
            elif pti == "f":
                # A floating point number
                params.append(_parse_float(dti))
            elif pti == "i":
                # An integer
                params.append(_parse_int(dti))
            elif pti == "I":
                # An integer or Nothing
                if nothing:
                    params.append(None)
                else:
                    params.append(_parse_int(dti))
            elif pti == "s":
                # A string
                params.append(dti)
            elif pti == "S":
                # A string or Nothing
                if nothing:
                    params.append(None)
                else:
                    params.append(dti)
            else:
                raise TypeError(f"GPS: Unexpected parameter type '{pti}'")
    except ValueError:
        # Something didn't parse, abort
        return None

    # Return the parsed data
    return params


# lint warning about too many attributes disabled
# pylint: disable-msg=R0902


[docs]class GPS: """GPS parsing module. Can parse simple NMEA data sentences from serial GPS modules to read latitude, longitude, and more. """ def __init__(self, uart, debug=False): self._uart = uart # Initialize null starting values for GPS attributes. self.timestamp_utc = None self.latitude = None self.longitude = None self.fix_quality = 0 self.fix_quality_3d = 0 self.satellites = None self.satellites_prev = None self.horizontal_dilution = None self.altitude_m = None self.height_geoid = None self.speed_knots = None self.track_angle_deg = None self._sats = None # Temporary holder for information from GSV messages self.sats = None # Completed information from GSV messages self.isactivedata = None self.true_track = None self.mag_track = None self.sat_prns = None self.sel_mode = None self.pdop = None self.hdop = None self.vdop = None self.total_mess_num = None self.mess_num = None self._raw_sentence = None self._mode_indicator = None self._magnetic_variation = None self.debug = debug
[docs] def update(self): """Check for updated data from the GPS module and process it accordingly. Returns True if new data was processed, and False if nothing new was received. """ # Grab a sentence and check its data type to call the appropriate # parsing function. try: sentence = self._parse_sentence() except UnicodeError: return None if sentence is None: return False if self.debug: print(sentence) data_type, args = sentence if len(data_type) < 5: return False data_type = bytes(data_type.upper(), "ascii") (talker, sentence_type) = _parse_talker(data_type) # Check for all currently known GNSS talkers # GA - Galileo # GB - BeiDou Systems # GI - NavIC # GL - GLONASS # GP - GPS # GQ - QZSS # GN - GNSS / More than one of the above if talker not in (b"GA", b"GB", b"GI", b"GL", b"GP", b"GQ", b"GN"): # It's not a known GNSS source of data # Assume it's a valid packet anyway return True result = True args = args.split(",") if sentence_type == b"GLL": # Geographic position - Latitude/Longitude result = self._parse_gll(args) elif sentence_type == b"RMC": # Minimum location info result = self._parse_rmc(args) elif sentence_type == b"GGA": # 3D location fix result = self._parse_gga(args) elif sentence_type == b"GSV": # Satellites in view result = self._parse_gsv(talker, args) elif sentence_type == b"GSA": # GPS DOP and active satellites result = self._parse_gsa(talker, args) return result
[docs] def send_command(self, command, add_checksum=True): """Send a command string to the GPS. If add_checksum is True (the default) a NMEA checksum will automatically be computed and added. Note you should NOT add the leading $ and trailing * to the command as they will automatically be added! """ self.write(b"$") self.write(command) if add_checksum: checksum = 0 for char in command: checksum ^= char self.write(b"*") self.write(bytes("{:02x}".format(checksum).upper(), "ascii")) self.write(b"\r\n")
@property def has_fix(self): """True if a current fix for location information is available.""" return self.fix_quality is not None and self.fix_quality >= 1 @property def has_3d_fix(self): """Returns true if there is a 3d fix available. use has_fix to determine if a 2d fix is available, passing it the same data""" return self.fix_quality_3d is not None and self.fix_quality_3d >= 2 @property def datetime(self): """Return struct_time object to feed rtc.set_time_source() function""" return self.timestamp_utc @property def nmea_sentence(self): """Return raw_sentence which is the raw NMEA sentence read from the GPS""" return self._raw_sentence
[docs] def read(self, num_bytes): """Read up to num_bytes of data from the GPS directly, without parsing. Returns a bytearray with up to num_bytes or None if nothing was read""" return self._uart.read(num_bytes)
[docs] def write(self, bytestr): """Write a bytestring data to the GPS directly, without parsing or checksums""" return self._uart.write(bytestr)
@property def in_waiting(self): """Returns number of bytes available in UART read buffer""" return self._uart.in_waiting
[docs] def readline(self): """Returns a newline terminated bytearray, must have timeout set for the underlying UART or this will block forever!""" return self._uart.readline()
def _read_sentence(self): # Parse any NMEA sentence that is available. # pylint: disable=len-as-condition # This needs to be refactored when it can be tested. # Only continue if we have at least 11 bytes in the input buffer if self.in_waiting < 11: return None sentence = self.readline() if sentence is None or sentence == b"" or len(sentence) < 1: return None try: sentence = str(sentence, "ascii").strip() except UnicodeError: return None # Look for a checksum and validate it if present. if len(sentence) > 7 and sentence[-3] == "*": # Get included checksum, then calculate it and compare. expected = int(sentence[-2:], 16) actual = 0 for i in range(1, len(sentence) - 3): actual ^= ord(sentence[i]) if actual != expected: return None # Failed to validate checksum. # copy the raw sentence self._raw_sentence = sentence return sentence # At this point we don't have a valid sentence return None def _parse_sentence(self): sentence = self._read_sentence() # sentence is a valid NMEA with a valid checksum if sentence is None: return None # Remove checksum once validated. sentence = sentence[:-3] # Parse out the type of sentence (first string after $ up to comma) # and then grab the rest as data within the sentence. delimiter = sentence.find(",") if delimiter == -1: return None # Invalid sentence, no comma after data type. data_type = sentence[1:delimiter] return (data_type, sentence[delimiter + 1 :]) def _update_timestamp_utc(self, time_utc, date=None): hours = time_utc // 10000 mins = (time_utc // 100) % 100 secs = time_utc % 100 if date is None: if self.timestamp_utc is None: day, month, year = 0, 0, 0 else: day = self.timestamp_utc.tm_mday month = self.timestamp_utc.tm_mon year = self.timestamp_utc.tm_year else: day = date // 10000 month = (date // 100) % 100 year = 2000 + date % 100 self.timestamp_utc = time.struct_time( (year, month, day, hours, mins, secs, 0, 0, -1) ) def _parse_gll(self, data): # GLL - Geographic Position - Latitude/Longitude if data is None or len(data) != 7: return False # Unexpected number of params. data = _parse_data(_GLL, data) if data is None: return False # Params didn't parse # Latitude self.latitude = _read_degrees(data, 0, "s") # Longitude self.longitude = _read_degrees(data, 2, "w") # UTC time of position self._update_timestamp_utc(int(data[4])) # Status Valid(A) or Invalid(V) self.isactivedata = data[5] # Parse FAA mode indicator self._mode_indicator = data[6] return True def _parse_rmc(self, data): # RMC - Recommended Minimum Navigation Information if data is None or len(data) not in (12, 13): return False # Unexpected number of params. data = _parse_data({12: _RMC, 13: _RMC_4_1}[len(data)], data) if data is None: return False # Params didn't parse # UTC time of position and date self._update_timestamp_utc(int(data[0]), data[8]) # Status Valid(A) or Invalid(V) self.isactivedata = data[1] if data[1].lower() == "a": if self.fix_quality == 0: self.fix_quality = 1 else: self.fix_quality = 0 # Latitude self.latitude = _read_degrees(data, 2, "s") # Longitude self.longitude = _read_degrees(data, 4, "w") # Speed over ground, knots self.speed_knots = data[6] # Track made good, degrees true self.track_angle_deg = data[7] # Magnetic variation if data[9] is None or data[10] is None: self._magnetic_variation = None else: self._magnetic_variation = _read_degrees(data, 9, "w") # Parse FAA mode indicator self._mode_indicator = data[11] return True def _parse_gga(self, data): # GGA - Global Positioning System Fix Data if data is None or len(data) != 14: return False # Unexpected number of params. data = _parse_data(_GGA, data) if data is None: return False # Params didn't parse # UTC time of position self._update_timestamp_utc(int(data[0])) # Latitude self.latitude = _read_degrees(data, 1, "s") # Longitude self.longitude = _read_degrees(data, 3, "w") # GPS quality indicator # 0 - fix not available, # 1 - GPS fix, # 2 - Differential GPS fix (values above 2 are 2.3 features) # 3 - PPS fix # 4 - Real Time Kinematic # 5 - Float RTK # 6 - estimated (dead reckoning) # 7 - Manual input mode # 8 - Simulation mode self.fix_quality = data[5] # Number of satellites in use, 0 - 12 self.satellites = data[6] # Horizontal dilution of precision self.horizontal_dilution = data[7] # Antenna altitude relative to mean sea level self.altitude_m = _parse_float(data[8]) # data[9] - antenna altitude unit, always 'M' ??? # Geoidal separation relative to WGS 84 self.height_geoid = _parse_float(data[10]) # data[11] - geoidal separation unit, always 'M' ??? # data[12] - Age of differential GPS data, can be null # data[13] - Differential reference station ID, can be null return True def _parse_gsa(self, talker, data): # GSA - GPS DOP and active satellites if data is None or len(data) not in (17, 18): return False # Unexpected number of params. if len(data) == 17: data = _parse_data(_GSA, data) else: data = _parse_data(_GSA_4_11, data) if data is None: return False # Params didn't parse talker = talker.decode("ascii") # Selection mode: 'M' - manual, 'A' - automatic self.sel_mode = data[0] # Mode: 1 - no fix, 2 - 2D fix, 3 - 3D fix self.fix_quality_3d = data[1] satlist = list(filter(None, data[2:-4])) self.sat_prns = [] for sat in satlist: self.sat_prns.append("{}{}".format(talker, sat)) # PDOP, dilution of precision self.pdop = _parse_float(data[14]) # HDOP, horizontal dilution of precision self.hdop = _parse_float(data[15]) # VDOP, vertical dilution of precision self.vdop = _parse_float(data[16]) # data[17] - System ID return True def _parse_gsv(self, talker, data): # GSV - Satellites in view # pylint: disable=too-many-branches if data is None or len(data) not in (7, 11, 15, 19): return False # Unexpected number of params. data = _parse_data( {7: _GSV7, 11: _GSV11, 15: _GSV15, 19: _GSV19}[len(data)], data, ) if data is None: return False # Params didn't parse talker = talker.decode("ascii") # Number of messages self.total_mess_num = data[0] # Message number self.mess_num = data[1] # Number of satellites in view self.satellites = data[2] sat_tup = data[3:] satlist = [] timestamp = time.monotonic() for i in range(len(sat_tup) // 4): j = i * 4 value = ( # Satellite number "{}{}".format(talker, sat_tup[0 + j]), # Elevation in degrees sat_tup[1 + j], # Azimuth in degrees sat_tup[2 + j], # signal-to-noise ratio in dB sat_tup[3 + j], # Timestamp timestamp, ) satlist.append(value) if self._sats is None: self._sats = [] for value in satlist: self._sats.append(value) if self.mess_num == self.total_mess_num: # Last part of GSV message if len(self._sats) == self.satellites: # Transfer received satellites to self.sats if self.sats is None: self.sats = {} else: # Remove all satellites which haven't # been seen for 30 seconds timestamp = time.monotonic() old = [] for i in self.sats: sat = self.sats[i] if (timestamp - sat[4]) > 30: old.append(i) for i in old: self.sats.pop(i) for sat in self._sats: self.sats[sat[0]] = sat self._sats.clear() self.satellites_prev = self.satellites return True
[docs]class GPS_GtopI2C(GPS): """GTop-compatible I2C GPS parsing module. Can parse simple NMEA data sentences from an I2C-capable GPS module to read latitude, longitude, and more. """ def __init__( self, i2c_bus, *, address=_GPSI2C_DEFAULT_ADDRESS, debug=False, timeout=5 ): import adafruit_bus_device.i2c_device as i2c_device # pylint: disable=import-outside-toplevel super().__init__(None, debug) # init the parent with no UART self._i2c = i2c_device.I2CDevice(i2c_bus, address) self._lastbyte = None self._charbuff = bytearray(1) self._internalbuffer = [] self._timeout = timeout
[docs] def read(self, num_bytes=1): """Read up to num_bytes of data from the GPS directly, without parsing. Returns a bytearray with up to num_bytes or None if nothing was read""" result = [] for _ in range(num_bytes): with self._i2c as i2c: # we read one byte at a time, verify it isnt part of a string of # 'stuffed' newlines and then append to our result array for byteification i2c.readinto(self._charbuff) char = self._charbuff[0] if (char == 0x0A) and (self._lastbyte != 0x0D): continue # skip duplicate \n's! result.append(char) self._lastbyte = char # keep track of the last character approved return bytearray(result)
[docs] def write(self, bytestr): """Write a bytestring data to the GPS directly, without parsing or checksums""" with self._i2c as i2c: i2c.write(bytestr)
@property def in_waiting(self): """Returns number of bytes available in UART read buffer, always 16 since I2C does not have the ability to know how much data is available""" return 16
[docs] def readline(self): """Returns a newline terminated bytearray, must have timeout set for the underlying UART or this will block forever!""" timeout = time.monotonic() + self._timeout while timeout > time.monotonic(): # check if our internal buffer has a '\n' termination already if self._internalbuffer and (self._internalbuffer[-1] == 0x0A): break char = self.read(1) if not char: continue self._internalbuffer.append(char[0]) # print(bytearray(self._internalbuffer)) if self._internalbuffer and self._internalbuffer[-1] == 0x0A: ret = bytearray(self._internalbuffer) self._internalbuffer = [] # reset the buffer to empty return ret return None # no completed data yet