Adafruit Ultimate GPS Example

adafruit_gps.py

# The MIT License (MIT)
#
# Copyright (c) 2017 Tony DiCola for Adafruit Industries
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
`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

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

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

# 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)

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


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 = None
        self.fix_quality_3d = None
        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
        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.debug = debug

    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
        data_type = bytes(data_type.upper(), "ascii")
        # return sentence
        if data_type == b'GPGLL':       # GLL, Geographic Position – Latitude/Longitude
            self._parse_gpgll(args)
        elif data_type == b'GPRMC':     # RMC, minimum location info
            self._parse_gprmc(args)
        elif data_type == b'GPGGA':     # GGA, 3d location fix
            self._parse_gpgga(args)
        return True

    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._uart.write(b'$')
        self._uart.write(command)
        if add_checksum:
            checksum = 0
            for char in command:
                checksum ^= char
            self._uart.write(b'*')
            self._uart.write(bytes('{:02x}'.format(checksum).upper(), "ascii"))
        self._uart.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

    def _parse_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 32 bytes in the input buffer
        if self._uart.in_waiting < 32:
            return None

        sentence = self._uart.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.
            # 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 _parse_gpgll(self, args):
        data = args.split(',')
        if data is None or data[0] is None:
            return  # Unexpected number of params.

        # Parse latitude and longitude.
        self.latitude = _parse_degrees(data[0])
        if self.latitude is not None and \
           data[1] is not None and data[1].lower() == 's':
            self.latitude *= -1.0
        self.longitude = _parse_degrees(data[2])
        if self.longitude is not None and \
           data[3] is not None and data[3].lower() == 'w':
            self.longitude *= -1.0
        time_utc = int(_parse_int(float(data[4])))
        if time_utc is not None:
            hours = time_utc // 10000
            mins = (time_utc // 100) % 100
            secs = time_utc % 100
            # Set or update time to a friendly python time struct.
            if self.timestamp_utc is not None:
                self.timestamp_utc = time.struct_time((
                    0, 0, 0, hours, mins, secs, 0, 0, -1))
            else:
                self.timestamp_utc = time.struct_time((0, 0, 0, hours, mins,
                                                       secs, 0, 0, -1))
        # Parse data active or void
        self.isactivedata = _parse_str(data[5])

    def _parse_gprmc(self, args):
        # Parse the arguments (everything after data type) for NMEA GPRMC
        # minimum location fix sentence.
        data = args.split(',')
        if data is None or len(data) < 11 or data[0] is None:
            return  # Unexpected number of params.
        # Parse fix time.
        time_utc = int(_parse_float(data[0]))
        if time_utc is not None:
            hours = time_utc // 10000
            mins = (time_utc // 100) % 100
            secs = time_utc % 100
            # Set or update time to a friendly python time struct.
            if self.timestamp_utc is not None:
                self.timestamp_utc = time.struct_time((
                    self.timestamp_utc.tm_year, self.timestamp_utc.tm_mon,
                    self.timestamp_utc.tm_mday, hours, mins, secs, 0, 0, -1))
            else:
                self.timestamp_utc = time.struct_time((0, 0, 0, hours, mins,
                                                       secs, 0, 0, -1))
        # Parse status (active/fixed or void).
        status = data[1]
        self.fix_quality = 0
        if status is not None and status.lower() == 'a':
            self.fix_quality = 1
        # Parse latitude and longitude.
        self.latitude = _parse_degrees(data[2])
        if self.latitude is not None and \
           data[3] is not None and data[3].lower() == 's':
            self.latitude *= -1.0
        self.longitude = _parse_degrees(data[4])
        if self.longitude is not None and \
           data[5] is not None and data[5].lower() == 'w':
            self.longitude *= -1.0
        # Parse out speed and other simple numeric values.
        self.speed_knots = _parse_float(data[6])
        self.track_angle_deg = _parse_float(data[7])
        # Parse date.
        if data[8] is not None and len(data[8]) == 6:
            day = int(data[8][0:2])
            month = int(data[8][2:4])
            year = 2000 + int(data[8][4:6])  # Y2k bug, 2 digit year assumption.
                                             # This is a problem with the NMEA
                                             # spec and not this code.
            if self.timestamp_utc is not None:
                # Replace the timestamp with an updated one.
                # (struct_time is immutable and can't be changed in place)
                self.timestamp_utc = time.struct_time((year, month, day,
                                                       self.timestamp_utc.tm_hour,
                                                       self.timestamp_utc.tm_min,
                                                       self.timestamp_utc.tm_sec,
                                                       0,
                                                       0,
                                                       -1))
            else:
                # Time hasn't been set so create it.
                self.timestamp_utc = time.struct_time((year, month, day, 0, 0,
                                                       0, 0, 0, -1))

    def _parse_gpgga(self, args):
        # Parse the arguments (everything after data type) for NMEA GPGGA
        # 3D location fix sentence.
        data = args.split(',')
        if data is None or len(data) != 14:
            return  # Unexpected number of params.
        # Parse fix time.
        time_utc = int(_parse_float(data[0]))
        if time_utc is not None:
            hours = time_utc // 10000
            mins = (time_utc // 100) % 100
            secs = time_utc % 100
            # Set or update time to a friendly python time struct.
            if self.timestamp_utc is not None:
                self.timestamp_utc = time.struct_time((
                    self.timestamp_utc.tm_year, self.timestamp_utc.tm_mon,
                    self.timestamp_utc.tm_mday, hours, mins, secs, 0, 0, -1))
            else:
                self.timestamp_utc = time.struct_time((0, 0, 0, hours, mins,
                                                       secs, 0, 0, -1))
        # Parse latitude and longitude.
        self.latitude = _parse_degrees(data[1])
        if self.latitude is not None and \
           data[2] is not None and data[2].lower() == 's':
            self.latitude *= -1.0
        self.longitude = _parse_degrees(data[3])
        if self.longitude is not None and \
           data[4] is not None and data[4].lower() == 'w':
            self.longitude *= -1.0
        # Parse out fix quality and other simple numeric values.
        self.fix_quality = _parse_int(data[5])
        self.satellites = _parse_int(data[6])
        self.horizontal_dilution = _parse_float(data[7])
        self.altitude_m = _parse_float(data[8])
        self.height_geoid = _parse_float(data[10])

    def _parse_gpgsa(self, args):
        data = args.split(',')
        if data is None:
            return  # Unexpected number of params

        # Parse selection mode
        self.sel_mode = _parse_str(data[0])
        # Parse 3d fix
        self.fix_quality_3d = _parse_int(data[1])
        satlist = list(filter(None, data[2:-4]))
        self.sat_prns = {}
        for i, sat in enumerate(satlist, 1):
            self.sat_prns["gps{}".format(i)] = _parse_int(sat)

        # Parse PDOP, dilution of precision
        self.pdop = _parse_float(data[-3])
        # Parse HDOP, horizontal dilution of precision
        self.hdop = _parse_float(data[-2])
        # Parse VDOP, vertical dilution of precision
        self.vdop = _parse_float(data[-1])

    def _parse_gpgsv(self, args):
        # Parse the arguments (everything after data type) for NMEA GPGGA
        # 3D location fix sentence.
        data = args.split(',')
        if data is None:
            return  # Unexpected number of params.

        # Parse number of messages
        self.total_mess_num = _parse_int(data[0])  # Total number of messages
        # Parse message number
        self.mess_num = _parse_int(data[1])  # Message number
        # Parse number of satellites in view
        self.satellites = _parse_int(data[2])  # Number of satellites

        if len(data) < 3:
            return

        sat_tup = data[3:]

        satdict = {}
        for i in range(len(sat_tup)/4):
            j = i*4
            key = "gps{}".format(i+(4*(self.mess_num-1)))
            satnum = _parse_int(sat_tup[0+j])  # Satellite number
            satdeg = _parse_int(sat_tup[1+j])  # Elevation in degrees
            satazim = _parse_int(sat_tup[2+j])  # Azimuth in degrees
            satsnr = _parse_int(sat_tup[3+j])  # signal-to-noise ratio in dB
            value = (satnum, satdeg, satazim, satsnr)
            satdict[key] = value

        if self.sats is None:
            self.sats = {}
        for satnum in satdict:
            self.sats[satnum] = satdict[satnum]

        try:
            if self.satellites < self.satellites_prev:
                for i in self.sats:
                    try:
                        if int(i[-2]) >= self.satellites:
                            del self.sats[i]
                    except ValueError:
                        if int(i[-1]) >= self.satellites:
                            del self.sats[i]
        except TypeError:
            pass
        self.satellites_prev = self.satellites

gps.py

#!/usr/bin/env python

import serial
import time
from adafruit_gps import GPS

port = "/dev/serial/by-id/usb-FTDI_FT232R_USB_UART_A506BOT5-if00-port0"

ser = serial.Serial(port, baudrate=9600, timeout=3000)
gps = GPS(ser)

"""
PMTK_A11.pdf pg 12
Data Field：
There are totally 19 data fields that present output frequencies for the 19 supported
NMEA sentences individually.
Supported NMEA Sentences
0 NMEA_SEN_GLL, // GPGLL interval - Geographic Position - Latitude longitude
1 NMEA_SEN_RMC, // GPRMC interval - Recommended Minimum Specific GNSS Sentence
2 NMEA_SEN_VTG, // GPVTG interval - Course over Ground and Ground Speed
3 NMEA_SEN_GGA, // GPGGA interval - GPS Fix Data
4 NMEA_SEN_GSA, // GPGSA interval - GNSS DOPS and Active Satellites
5 NMEA_SEN_GSV, // GPGSV interval - GNSS Satellites in View
6 //Reserved
7 //Reserved
13 //Reserved
14 //Reserved
15 //Reserved
16 //Reserved
17 //Reserved
18 NMEA_SEN_MCHN, // PMTKCHN interval – GPS channel status
Supported Frequency Setting
0 - Disabled or not supported sentence
1 - Output once every one position fix
2 - Output once every two position fixes
3 - Output once every three position fixes
4 - Output once every four position fixes
5 - Output once every five position fixes
Example:
$PMTK314,1,1,1,1,1,5,0,0,0,0,0,0,0,0,0,0,0,0,0*2C<CR><LF>
"""
# gps.send_command(b'PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0') # minimum
gps.send_command(b'PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0') # setup typical
# gps.send_command(b'PMTK314,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0') # everything
gps.send_command(b'PMTK220,1000')  # 1 Hz
# gps.send_command(b'PMTK220,500')  # 2 Hz, 500 msec

for i in range(10):
    # data = ser.read(1024)
    # print(data, flush=True)
    time.sleep(0.5)

    ok = gps.update()
    if not ok or gps.has_fix is False:
        print("no data")
    else:
        print('=' * 40)  # Print a separator line.
        print("Fix:", gps.has_fix)
        print("Satellites:", gps.satellites)
        print("Sats:", gps.sats)
        print('Latitude: {0:.6f} degrees'.format(gps.latitude))
        print('Longitude: {0:.6f} degrees'.format(gps.longitude))
        print("Alititude [m]:", gps.altitude_m)
        print("Altitude Geod [m]", gps.height_geoid)
        print("Speed [knots]:", gps.speed_knots)
        print("Dop: {} {} {}".format(gps.pdop, gps.hdop, gps.vdop))
        print("Fix: {} {}".format(gps.fix_quality, gps.fix_quality_3d))
        print("PRNs:", gps.sat_prns)
        # print("Fix Raw timestamp:", gps.timestamp_utc)
        print('Fix timestamp: {:02}/{:02}/{} {:02}:{:02}:{:02}'.format(
            gps.timestamp_utc.tm_mon,   # Grab parts of the time from the
            gps.timestamp_utc.tm_mday,  # struct_time object that holds
            gps.timestamp_utc.tm_year,  # the fix time.  Note you might
            gps.timestamp_utc.tm_hour,  # not get all data like year, day,
            gps.timestamp_utc.tm_min,   # month!
            gps.timestamp_utc.tm_sec))

output.txt

...========================================
Fix: True
Satellites: 8
Sats: None
Latitude: 38.750747 degrees
Longitude: -77.247683 degrees
Alititude [m]: 80.4
Altitude Geod [m] -33.5
Speed [knots]: 0.05
Dop: None None None
Fix: 1 None
PRNs: None
Fix timestamp: 07/07/2019 16:58:28
========================================
Fix: True
Satellites: 8
Sats: None
Latitude: 38.750742 degrees
Longitude: -77.247682 degrees
Alititude [m]: 80.5
Altitude Geod [m] -33.5
Speed [knots]: 0.05
Dop: None None None
Fix: 1 None
PRNs: None
Fix timestamp: 07/07/2019 16:58:29
========================================
Fix: True
Satellites: 8
Sats: None
Latitude: 38.750742 degrees
Longitude: -77.247682 degrees
Alititude [m]: 80.5
Altitude Geod [m] -33.5
Speed [knots]: 0.14
Dop: None None None
Fix: 1 None
PRNs: None
Fix timestamp: 07/07/2019 16:58:29
...