Introduction¶

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

Dependencies¶

This driver depends on:

Adafruit CircuitPython

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle.

Installing from PyPI¶

On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI. To install for current user:

pip3 install adafruit-circuitpython-gps

To install system-wide (this may be required in some cases):

sudo pip3 install adafruit-circuitpython-gps

To install in a virtual environment in your current project:

mkdir project-name && cd project-name
python3 -m venv .env
source .env/bin/activate
pip3 install adafruit-circuitpython-gps

Usage Example¶

See examples/gps_simpletest.py for a demonstration of parsing and printing GPS location.

Important: Feather boards and many other circuitpython boards will round to two decimal places like this:

>>> float('1234.5678')
1234.57

This isn’t ideal for GPS data as this lowers the accuracy from 0.1m to 11m.

This can be fixed by using string formatting when the GPS data is output.

An implementation of this can be found in examples/gps_simpletest.py

import time
import board
import busio

import adafruit_gps

RX = board.RX
TX = board.TX

uart = busio.UART(TX, RX, baudrate=9600, timeout=30)

gps = adafruit_gps.GPS(uart, debug=False)

gps.send_command(b'PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')

gps.send_command(b'PMTK220,1000')

last_print = time.monotonic()
while True:

    gps.update()

    current = time.monotonic()
    if current - last_print >= 1.0:
        last_print = current
        if not gps.has_fix:
            print('Waiting for fix...')
            continue
        print('=' * 40)  # Print a separator line.
        print('Latitude: {0:.6f} degrees'.format(gps.latitude))
        print('Longitude: {0:.6f} degrees'.format(gps.longitude))

These two lines are the lines that actually solve the issue:

print('Latitude: {0:.6f} degrees'.format(gps.latitude))
print('Longitude: {0:.6f} degrees'.format(gps.longitude))

Note: Sending multiple PMTK314 packets with gps.send_command() will not work unless there is a substantial amount of time in-between each time gps.send_command() is called. A time.sleep() of 1 second or more should fix this.

About NMEA Data¶

This GPS module uses the NMEA 0183 protocol.

This data is formatted by the GPS in one of two ways.

The first of these is GGA. GGA has more or less everything you need.

Here’s an explanation of GGA:

                                                    11
       1         2       3 4        5 6 7  8   9  10 |  12 13  14   15
       |         |       | |        | | |  |   |   | |   | |   |    |
$--GGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh

Time (UTC)
Latitude
N or S (North or South)
Longitude
E or W (East or West)
GPS Quality Indicator,
- 0 - fix not available,
- 1 - GPS fix,
- 2 - Differential GPS fix
Number of satellites in view, 00 - 12
Horizontal Dilution of precision
Antenna Altitude above/below mean-sea-level (geoid)
Units of antenna altitude, meters
Geoidal separation, the difference between the WGS-84 earth ellipsoid and mean-sea-level (geoid), “-” means mean-sea-level below ellipsoid
Units of geoidal separation, meters
Age of differential GPS data, time in seconds since last SC104 type 1 or 9 update, null field when DGPS is not used
Differential reference station ID, 0000-1023
Checksum

The second of these is RMC. RMC is Recommended Minimum Navigation Information.

Here’s an explanation of RMC:

                                                           12
       1         2 3       4 5        6 7   8   9   10   11|
       |         | |       | |        | |   |   |    |   | |
$--RMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,xxxx,x.x,a*hh

Time (UTC)
Status, V = Navigation receiver warning
Latitude
N or S
Longitude
E or W
Speed over ground, knots
Track made good, degrees true
Date, ddmmyy
Magnetic Variation, degrees
E or W
Checksum

Info about NMEA taken from here.

Contributing¶

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.

Documentation¶

For information on building library documentation, please check out this guide.

Table of Contents¶

Simple test¶

Ensure your device works with this simple test.

examples/gps_simpletest.py¶

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

# Simple GPS module demonstration.
# Will wait for a fix and print a message every second with the current location
# and other details.
import time
import board
import busio

import adafruit_gps

# Create a serial connection for the GPS connection using default speed and
# a slightly higher timeout (GPS modules typically update once a second).
# These are the defaults you should use for the GPS FeatherWing.
# For other boards set RX = GPS module TX, and TX = GPS module RX pins.
uart = busio.UART(board.TX, board.RX, baudrate=9600, timeout=10)

# for a computer, use the pyserial library for uart access
# import serial
# uart = serial.Serial("/dev/ttyUSB0", baudrate=9600, timeout=10)

# If using I2C, we'll create an I2C interface to talk to using default pins
# i2c = board.I2C()

# Create a GPS module instance.
gps = adafruit_gps.GPS(uart, debug=False)  # Use UART/pyserial
# gps = adafruit_gps.GPS_GtopI2C(i2c, debug=False)  # Use I2C interface

# Initialize the GPS module by changing what data it sends and at what rate.
# These are NMEA extensions for PMTK_314_SET_NMEA_OUTPUT and
# PMTK_220_SET_NMEA_UPDATERATE but you can send anything from here to adjust
# the GPS module behavior:
#   https://cdn-shop.adafruit.com/datasheets/PMTK_A11.pdf

# Turn on the basic GGA and RMC info (what you typically want)
gps.send_command(b"PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0")
# Turn on just minimum info (RMC only, location):
# gps.send_command(b'PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')
# Turn off everything:
# gps.send_command(b'PMTK314,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')
# Turn on everything (not all of it is parsed!)
# gps.send_command(b'PMTK314,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0')

# Set update rate to once a second (1hz) which is what you typically want.
gps.send_command(b"PMTK220,1000")
# Or decrease to once every two seconds by doubling the millisecond value.
# Be sure to also increase your UART timeout above!
# gps.send_command(b'PMTK220,2000')
# You can also speed up the rate, but don't go too fast or else you can lose
# data during parsing.  This would be twice a second (2hz, 500ms delay):
# gps.send_command(b'PMTK220,500')

# Main loop runs forever printing the location, etc. every second.
last_print = time.monotonic()
while True:
    # Make sure to call gps.update() every loop iteration and at least twice
    # as fast as data comes from the GPS unit (usually every second).
    # This returns a bool that's true if it parsed new data (you can ignore it
    # though if you don't care and instead look at the has_fix property).
    gps.update()
    # Every second print out current location details if there's a fix.
    current = time.monotonic()
    if current - last_print >= 1.0:
        last_print = current
        if not gps.has_fix:
            # Try again if we don't have a fix yet.
            print("Waiting for fix...")
            continue
        # We have a fix! (gps.has_fix is true)
        # Print out details about the fix like location, date, etc.
        print("=" * 40)  # Print a separator line.
        print(
            "Fix timestamp: {}/{}/{} {: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,
            )
        )
        print("Latitude: {0:.6f} degrees".format(gps.latitude))
        print("Longitude: {0:.6f} degrees".format(gps.longitude))
        print("Fix quality: {}".format(gps.fix_quality))
        # Some attributes beyond latitude, longitude and timestamp are optional
        # and might not be present.  Check if they're None before trying to use!
        if gps.satellites is not None:
            print("# satellites: {}".format(gps.satellites))
        if gps.altitude_m is not None:
            print("Altitude: {} meters".format(gps.altitude_m))
        if gps.speed_knots is not None:
            print("Speed: {} knots".format(gps.speed_knots))
        if gps.track_angle_deg is not None:
            print("Track angle: {} degrees".format(gps.track_angle_deg))
        if gps.horizontal_dilution is not None:
            print("Horizontal dilution: {}".format(gps.horizontal_dilution))
        if gps.height_geoid is not None:
            print("Height geo ID: {} meters".format(gps.height_geoid))

`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
Adafruit Ultimate GPS FeatherWing

Software and Dependencies:

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

class adafruit_gps.GPS(uart, debug=False)[source]¶

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

datetime¶: Return struct_time object to feed rtc.set_time_source() function

has_3d_fix¶: 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

has_fix¶: True if a current fix for location information is available.

in_waiting¶: Returns number of bytes available in UART read buffer

nmea_sentence¶: Return raw_sentence which is the raw NMEA sentence read from the GPS

read(num_bytes)[source]¶: 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

readline()[source]¶: Returns a newline terminated bytearray, must have timeout set for the underlying UART or this will block forever!

send_command(command, add_checksum=True)[source]¶: 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!

update()[source]¶: 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.

write(bytestr)[source]¶: Write a bytestring data to the GPS directly, without parsing or checksums

class adafruit_gps.GPS_GtopI2C(i2c_bus, *, address=16, debug=False, timeout=5)[source]¶

GTop-compatible I2C GPS parsing module. Can parse simple NMEA data sentences from an I2C-capable GPS module to read latitude, longitude, and more.

in_waiting¶: Returns number of bytes available in UART read buffer, always 32 since I2C does not have the ability to know how much data is available

read(num_bytes=1)[source]¶: 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

readline()[source]¶: Returns a newline terminated bytearray, must have timeout set for the underlying UART or this will block forever!

write(bytestr)[source]¶: Write a bytestring data to the GPS directly, without parsing or checksums

Introduction¶

Dependencies¶

Installing from PyPI¶

Usage Example¶

About NMEA Data¶

Contributing¶

Documentation¶

Table of Contents¶

Simple test¶

adafruit_gps¶

Implementation Notes¶

Indices and tables¶

`adafruit_gps`¶