T-Echo LoRa APRS Tracker Firmware
Ultra-low-power custom APRS tracker firmware for the LILYGO T-Echo that uses the nRF52840's deep-sleep modes to achieve 100 µA standby current while transmitting GPS positions over LoRa.
Overview
This custom firmware by cfr34k transforms the LILYGO T-Echo into an extremely power-efficient LoRa APRS tracker. Unlike the ESP32-based T-Beam, the T-Echo's nRF52840 SoC is designed for ultra-low-power operation — and this firmware exploits that fully, achieving standby currents down to 100 µA while maintaining BLE connectivity, far below what an ESP32 can achieve. The result is a tiny, wearable APRS tracker with exceptional battery life.
How It Works
The firmware polls the L76K GNSS module for position fixes and transmits compressed APRS packets via the SX1262 LoRa transceiver. Smart beaconing logic adapts the transmission rate based on movement speed and heading change: slow movement sends fewer beacons, fast or turning movement sends more frequently, conserving battery without sacrificing tracking quality. Received packets are decoded and displayed on the e-paper screen, showing nearby stations with their callsign, distance, and bearing.
Key Features
The e-paper display supports partial refresh for updating only changed content, and the Bluetooth LE interface allows reconfiguring the tracker from a phone app without a USB cable. Transmission power is configurable up to +22 dBm, matching the SX1262's maximum output. APRS compressed format encoding minimizes packet length. The project is fully open-source and targeted at the amateur radio community wanting a discreet, long-runtime wearable tracker compatible with the existing LoRa APRS iGate infrastructure.
