Ethernet Radio Bridge — Firmware

STM32F407-based device that bridges a repeater radio's audio + control (COR/PTT, CTCSS/DCS) to an AllStarLink node over Ethernet using the USRP UDP protocol (chan_usrp). It replaces the traditional Raspberry Pi + USB sound-card setup with a single purpose-built board.

Full hardware design rationale lives in ethernet-radio-bridge-design.md. This repository is the firmware + web UI.

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Repository layout

src/
  proto/      USRP wire codec (portable, byte-accurate, host-tested)
  dsp/        ringbuf, biquad, goertzel(CTCSS decode), dds(CTCSS encode),
              golay23 + dcs, jitter_buffer (drop/insert for clock drift)
  config/     versioned binary config struct, crc32, A/B flash store, JSON-for-web
  sys/        leveled logging, assert, timebase/RTC iface, watchdog supervisor
  bsp/        board init / pins / clocks  (nucleo_f429zi | board_f407)   [target]
  hal_glue/   thin HAL wrappers: adc_dma, dac_dma, gpio_io, spi_flash, ...  [target]
  net/        lwIP glue, usrp_engine, httpd + Basic auth, sntp, mdns        [target]
  app/        FreeRTOS tasks (audio/network/web/env) + supervisor + main    [target]
tests/        Unity host unit tests for every portable module
web/          configuration UI (vanilla HTML/CSS/JS, gzip-packed into flash)
tools/        fetch_deps.sh, webfs_pack.py, usrp_sim.py
linker/       memory maps (CCM-aware, bootloader + A/B app banks)
docs/         architecture, memory map, pinmap, verified USRP protocol notes
cmake/        arm-none-eabi toolchain + firmware dependency locator

proto/, dsp/, config/ and the portable parts of sys/ compile on the host and are covered by unit tests. Everything under bsp/, hal_glue/, net/, app/ is target-only (needs STM32 HAL / FreeRTOS / lwIP).

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Quick start — run the host unit tests

No embedded toolchain required; just a host C compiler, CMake and Python 3.

git submodule update --init third_party/unity   # one-time (Unity test framework)
./scripts/run_tests.sh                           # configure + build + ctest

or manually:

cmake --preset host
cmake --build --preset host
ctest --preset host

Build the firmware (at hardware bring-up)

./tools/fetch_deps.sh                 # pull STM32 HAL/CMSIS, FreeRTOS, lwIP
cmake --preset firmware-f429zi        # or firmware-f407
cmake --build --preset firmware-f429zi
# -> build/f429zi/firmware.elf (+ .bin/.hex)

The ARM toolchain (arm-none-eabi-gcc) and the middleware are intentionally not required for the host test build, so CI and contributors can validate the DSP/protocol/config logic without any hardware or vendor SDK.

Pack the web UI into a flash image

python3 tools/webfs_pack.py web/ build/webfs.img --cheader src/net/webfs_data.h

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Status

Scaffold stage. The portable core (USRP codec, CTCSS/DCS DSP, jitter buffer, config store) is implemented and unit-tested. The target layers (bsp/, hal_glue/, net/, app/) are interface-complete stubs ready to be filled in on real hardware — see docs/architecture.md and the TODO(hw): markers.

License

TBD. Intended: MIT for this firmware. Third-party components retain their own licenses — see THIRD_PARTY_LICENSES.md.