Pocket GPS Tracker and Trip Logger

A GPS module speaks simple text sentences (NMEA) over serial. The Pico reads them, stores your position every few seconds in its flash memory and syncs when it sees your home Wi-Fi.

Video tutorial

▶ Circuit DigestWatch on YouTube ↗

Video by Circuit Digest, embedded from YouTube. The written steps below are our own and match the parts list.

Mission steps

1. Wire the GPS

   GPS TX to Pico GP1 (UART0 RX), GPS RX to GP0, power from 3V3 and GND.

2. Get a fix

   Go outside. A cold start can take a minute or more; the module's LED usually blinks once it has a fix.

3. Parse NMEA

   Read $GNRMC/$GPRMC sentences for latitude, longitude, speed and time.

4. Log efficiently

   Write one line every 5–10 seconds. Flash memory has limited write cycles, so buffer and write in batches.

5. Respect privacy

   Only track yourself or people who clearly agree to it. Hidden tracking of others is illegal in many places.

Code

# MicroPython on Pico 2 W
from machine import UART, Pin
import time

gps = UART(0, baudrate=9600, tx=Pin(0), rx=Pin(1))

def to_deg(v, d):
    if not v: return None
    deg = int(float(v) / 100); mins = float(v) - deg * 100
    val = deg + mins / 60
    return -val if d in ('S', 'W') else val

buf = []
while True:
    line = gps.readline()
    if line and (line.startswith(b'$GNRMC') or line.startswith(b'$GPRMC')):
        f = line.decode('ascii', 'ignore').split(',')
        if len(f) > 6 and f[2] == 'A':                    # A = valid fix
            buf.append('%s,%.6f,%.6f\n' % (f[1], to_deg(f[3], f[4]), to_deg(f[5], f[6])))
    if len(buf) >= 12:
        with open('track.csv', 'a') as out:
            out.write(''.join(buf))
        buf = []
        time.sleep(5)

Tip: test every script on the bench before installing it in a moving machine.

Questions