FlexAudioLink

Low-latency wireless audio bridge.

Motivation and Use-cases

originally built as a wireless transceiver for a gaming headset retrofit. The hardware can also support:

• Wireless audio relay (e.g. room-to-room)
• BLE audio bridging (phone/laptop as central to a FlexAudioLink node)
• Flexible audio paths such as USB-to-analog, USB-to-USB, analog-to-analog, and BLE bridges

Note: Most of these are not yet implemented; see Project Status.

Features

• Audio bridge endpoints: USB Audio Class device, I2S/analog codec, BLE
• Low-latency wireless link between devices
• USB CDC CLI for device configuration
• Web UI (Svelte) with WebSerial and WebSocket-to-serial bridge
• Single hardware design: nRF54LM20A + NAU88L21 + nPM1300

Architecture

The diagram below shows the typical dongle/headset setup: dongle on the left, headset on the right. Both run the same hardware and firmware.

USB handles audio on the dongle side, I2S/codec on the headset side.

Project Status

Implemented:

• USB device (UAC + CDC)
• Configuration persistence
• USB CDC CLI
• PROP radio test mode
• Audio I2S / codec integration
• Wireless audio streaming (USB ↔ I2S)

In progress:

• Schematic
• Update Docs

Planned:

• PCB layout
• Arbitrary Source/Sink combinations
• Analog multiplexing
• Packet Loss Concealment
• BLE audio transport
• Web UI

Under evaluation:

• Adaptive Frequency Hopping
• Clear Channel Assessment

Documentation

Full documentation.

Key pages:

• Getting Started — toolchain setup, build, and flash instructions
• Firmware — architecture, PROP protocol
• Hardware — schematic, PCB, rationale for chosen components
• Web UI — setup and configuration
• CLI Reference — available CLI commands

Note: the documentation is a work in progress and nowhere near complete.

Repository Layout

• firmware/: active Zephyr-based firmware for nrf54lm20dk/nrf54lm20a/cpuapp
• webui/: Svelte configuration UI plus Python WebSocket-to-serial bridge
• hardware/: KiCad project and hardware notes
• python/: standalone utilities for signal generation and latency/error experiments
• devel_notes/: bring-up and development references