# 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
_ST_MIN = _GLL
_ST_MAX = _GSV19
_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",
)
# 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) != 12:
return False # Unexpected number of params.
data = _parse_data(_RMC, 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