A GPS module unlocks Rescue mode, on-screen speed/altitude data, and position logging. While plug-and-play modules like BN-220 cost $15, building your own teaches you the protocol and hardware.
Core Hardware
GNSS Receiver: u-blox NEO-M8N tracks GPS+GLONASS+BeiDou simultaneously — 26s cold start, 2.5m accuracy. NEO-6M is cheaper ($5) but GPS-only and slower.
Microcontroller: Arduino Nano handles NMEA parsing. ESP32-C3 ($3) adds WiFi/Bluetooth for wireless telemetry.
Wiring and Protocol
NEO-M8N communicates over UART at 9600 baud (NMEA-0183). Connections: VCC to 5V, GND to GND, TX to Arduino D2 (SoftwareSerial RX), RX to D3 (TX). Use TinyGPS++ library to parse $GPRMC and $GPGGA sentences.
For Betaflight: connect GPS TX to a free UART RX on the FC. Enable GPS in Configuration, set UART in Ports, verify in GPS tab.
Advanced Features
OLED display (SSD1306) for live position. SD card logging for GPX replay in Google Earth. LoRa telemetry (SX1278) for kilometer-range ground tracking.
Total cost: $20-30. Configure with u-blox u-center for update rate (up to 10Hz) and constellation selection.
