dartt_audio

A library for streaming audio to embedded targets over UART using the DARTT protocol.

ffmpeg usage: In order to properly parse the audio file (.wav only) it must be properly encoded. This program expects very simple encoding. It must be MONO, and it should be encoded for a specific baud rate.

In order to determine the re-encoding rate, use the simple formula: `baud/40'. This comes from: two bytes per sample (payload), two bytes header (COBS), 10 bits per byte = 40 bits, baud rate is bits/sec.

So the workflow for 921600 baud playback is:

yt-dlp 'url to audio'
ffmpeg -i audio.m4a audio.wav
ffmpeg -i audio.wav -ar 23040 -ac 1 audioReadyToGo.wav
wav-to-uart audioReadyToGo.wav

-ar alters the sampling rate, -ac changes channel count

To scale the volume using ffmpeg to the achievable system range:

ffmpeg -i input.wav -af "volume=690/32767" -c:a pcm_s16le output.wav

Linking (CMake)

dartt_audio is designed to be consumed via add_subdirectory. It expects dartt-protocol, serial-cross-platform, and byte-stuffing to be available as CMake targets. If the parent project has already added those subdirectories, dartt_audio will reuse their targets automatically. If not, it will pull them from its own external/ directory.

# In your parent CMakeLists.txt:
add_subdirectory(external/dartt-protocol)
add_subdirectory(external/serial-cross-platform)
add_subdirectory(external/byte-stuffing)
add_subdirectory(external/dartt_audio)   # reuses the targets above

target_link_libraries(your_target PRIVATE dartt_audio)

Or, if you want dartt_audio to manage its own copies of those dependencies:

add_subdirectory(external/dartt_audio)
target_link_libraries(your_target PRIVATE dartt_audio)

The consumer's include path will automatically pick up AudioWriter.h, wav_parsing.h, dr_wav.h, and audio.h.

Note: DR_WAV_IMPLEMENTATION must be defined in exactly one translation unit in the consuming project before the first include of any dartt_audio header in that TU (see examples/example_playback.cpp for the pattern).

Building the example

cmake -B build -DDARTT_AUDIO_BUILD_EXAMPLES=ON [-DCMAKE_BUILD_TYPE=Debug]
cmake --build build
./build/bin/example_playback <file.wav> <dartt_address> <dartt_index> [--baudrate <baud>]

Linking for Embedded

The embedded/ directory is meant to be submoduled into whatever embedded build compilation toolchain you have. I.e. for STM32CubeIDE, the recommended flow is:

1. Submodule this repo
2. Update the .project/.cproject settings to include external/dartt_audio/embedded/ — i.e. link audio.c and audio.h from the submoduled repo

That's it!