Raspberry Pi Pico W with GPS processed data
Example code of connecting the Raspberry Pi Pico W to a GPS module. Checking the checksum and extract some gps information.
Connections
| Description | Colour | Pico W | GPS module |
|---|---|---|---|
| Power 3v | Orange | pin36 3V3(OUT) | 3.3v |
| Ground | Black | pin3 GND | GND |
| Pico W Transmit | Yellow | pin6 GP4 UART1_TX | GPS RX pin |
| Pico W Receive | Green | pin7 GP5 UART1_RX | GPS TX pin |
Photo
Sketch
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| # Raspberry Pi Pico W - GPS module - processed | |
| # Copyright (C) 2023 https://www.roboticboat.uk | |
| # e3897b8c-d8b6-46c9-b16b-cfcd25f0ee4a | |
| # | |
| # This program is free software: you can redistribute it and/or modify | |
| # it under the terms of the GNU General Public License as published by | |
| # the Free Software Foundation, either version 3 of the License, or | |
| # (at your option) any later version. | |
| # | |
| # This program is distributed in the hope that it will be useful, | |
| # but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| # GNU General Public License for more details. | |
| # | |
| # You should have received a copy of the GNU General Public License | |
| # along with this program. If not, see <https://www.gnu.org/licenses/>. | |
| # These Terms shall be governed and construed in accordance with the laws of | |
| # England and Wales, without regard to its conflict of law provisions. | |
| # | |
| # User Interface https://thonny.org/ | |
| # | |
| # The objective of the code snippest is to show GPS statements being processed | |
| # without relying on a library, where for beginners, code gets buried | |
| from machine import Pin,UART | |
| import time | |
| import sys | |
| # Initialise the Serial port | |
| uart = UART(1, baudrate=9600, tx=Pin(4), rx=Pin(5)) | |
| # Initialise the Serial port message protocol | |
| uart.init(bits=8, parity=None, stop=1) | |
| # Define the LED pin | |
| led = Pin("LED", Pin.OUT) | |
| # Initialise variables | |
| gpsmessage = "" | |
| gpstime = "" | |
| gpslatitude = "" | |
| gpsNS = "" | |
| gpslongitude = "" | |
| gpsEW = "" | |
| gpsSatellites = "" | |
| try: | |
| # Infinite loop, like on the Arudino | |
| while True: | |
| # If data waiting to be read | |
| if uart.any(): | |
| # Read data on the Serial port. We don't need to wait for a full line | |
| data = uart.read() | |
| # Have to wrap the decoder in error capturing as the starting | |
| # GPS characters might not be ASCII until Serial aligns | |
| # Ideally data is checked first and error capturing not used | |
| try: | |
| # Decode the bytes into a str class | |
| asciiCharacters = data.decode("utf-8") | |
| except: | |
| continue | |
| # Loop over the characters of the message | |
| for nextChar in asciiCharacters: | |
| # Do we see a '$' character? | |
| if nextChar == "$": | |
| # Start of the next message, so also last of the previous | |
| # message. So we can process to received GPS statement | |
| # Update the User | |
| print(gpsmessage) | |
| # Look out for GGA messages | |
| # Can process the message - 3rd, 4th & 5th characters | |
| if (gpsmessage[2:5] == "GGA"): | |
| # Split the message using commas into a list of items | |
| items = gpsmessage.split(",") | |
| # Number of items. This should be 15 items | |
| nitems = len(items) | |
| # Checksum is the last item. It will also contain * '\r' and '\n' | |
| # Is the checksum item the correct length | |
| if len(items[nitems-1]) == 5: | |
| # Read the checksum from the message | |
| # Ignore the * \r and \n | |
| checksum = items[nitems-1][1:3] | |
| # Convert the double HEX checksum to an integer | |
| cksum = int(checksum,16) | |
| # Loop over the message characters | |
| # Stop before the last * checksum and '\r' '\n' | |
| for gpschar in gpsmessage[:len(gpsmessage)-5]: | |
| # The ord() function returns an integer | |
| # representing the Unicode character | |
| cksum ^= ord(gpschar) | |
| # Is the checksum correct? Needs to equal zero | |
| if (cksum == 0): | |
| # Extract gps information | |
| gpstime = items[1] | |
| gpslatitude = items[2] | |
| gpsNS = items[3] | |
| gpslongitude = items[4] | |
| gpsEW = items[5] | |
| gpsSatellites = items[7] | |
| # Update the User | |
| print(gpstime) | |
| print(gpslatitude) | |
| print(gpsNS) | |
| print(gpslongitude) | |
| print(gpsEW) | |
| print(gpsSatellites) | |
| print("") | |
| # Toggle the LED light on/off | |
| led.toggle() | |
| # Initialise the next new message | |
| gpsmessage = "" | |
| else: | |
| # Append the next character | |
| gpsmessage += nextChar | |
| # Interrupt handing | |
| # Capture the CTRL + C event | |
| except (KeyboardInterrupt, SystemExit): | |
| # Update the user | |
| print ("Well done. Finished\n") |