OpenRTX — Open-Source Firmware for SA868 Two-Way Radios
Open-source firmware replacing the proprietary SA868 radio module code on the T-TWR, enabling the M17 digital voice protocol — a modern, royalty-free digital voice standard for amateur radio.
Overview
OpenRTX is an established open-source firmware project for digital amateur radios. The sa8x8-fw component specifically targets the NiceRF SA868 UHF/VHF transceiver module used in the LILYGO T-TWR and T-TWR Plus, replacing the proprietary firmware with open-source code and enabling the M17 digital voice protocol.
Key Features
- M17 Digital Voice: Implements M17 — a modern, royalty-free, open-source digital voice protocol for amateur radio, using the Codec2 vocoder
- Open SA868 Firmware: Replaces the closed-source firmware on the SA868 radio module with fully open code
- VHF/UHF Operation: Full transmit and receive on amateur VHF (144 MHz) and UHF (430 MHz) bands
- OLED Display: Status, frequency, and signal info on the T-TWR's built-in OLED
- Rotary Encoder: Tune frequencies and navigate menus via the rotary control
- GPS Integration: Position reporting for APRS tracking (T-TWR Plus with L76K GNSS)
Getting Started
Flash the sa8x8-fw firmware to the SA868 module and the OpenRTX firmware to the ESP32-S3 host controller via PlatformIO. This is an advanced project requiring familiarity with the T-TWR hardware and amateur radio licensing (a ham radio license is required to transmit).
Why This Project
M17 is the first truly open digital voice mode for amateur radio — no patent royalties, no proprietary codecs (unlike DMR, D-STAR, or System Fusion). The T-TWR with OpenRTX becomes one of the most affordable M17-capable radios available. For ham radio operators who value open standards, this project represents the future of amateur digital voice communications.
