Teenage Engineering's PO-32 acoustic modem and synth implementation

libpo32 is a lightweight C99 library that reimplements the PO-32 Tonic's acoustic transfer protocol and drum synthesis engine, designed for embedded systems and bare-metal environments.

A small C99 library for Teenage Engineering PO-32 acoustic data transfers and drum synthesis.

libpo32

reimplements the PO-32 Tonic transfer stack and a compatible drum voice model. It is not a full PO-32 firmware or UI emulator; it covers the packet format, acoustic modem, frame decoder, and local drum synthesis needed to build, send, receive, and preview PO-32 transfers.

Overview
Using It With a PO-32
Getting Started
Examples
Public API
Documentation
Project Layout
Contributing
License

| Area | What libpo32 provides | |---|---| | Transfer protocol | Build and parse PO-32 patch, pattern, and state packets | | Acoustic modem | Render transfer frames to DPSK audio for playback into the device | | Decoder | Recover normalized frames and packets from transfer audio | | Drum synthesis | Render the PO-32's 21-parameter drum voice locally for preview and testing |

The core is freestanding C99: no libc runtime, no external DSP libraries, no platform audio APIs, no file I/O. Only the freestanding headers <stddef.h>

and <stdint.h>

are used. Suitable for embedded targets and bare-metal environments.

The PO-32 is not receiving finished drum audio when you transfer a sound or a pattern. It receives structured data:

| Data | Meaning | |---|---| | Patch packets | The two patch endpoints per instrument (Left and Right ), with the destination instrument slot encoded in the packet | | Pattern packets | Which instruments trigger on which steps, with the destination pattern slot encoded as pattern_number | | State packet | Tempo, swing, morph defaults, and the transferred pattern list |

The device then uses its own internal synth engine to turn those parameters into sound.

At a high level, the workflow with real hardware is:

| Step | What you do | |---|---| | 1 | Build a transfer in software from patch, pattern, and state data | | 2 | Render that transfer to a WAV or live audio stream | | 3 | Put the PO-32 into its normal receive/import flow | | 4 | Play the rendered transfer audio into the device | | 5 | The PO-32 decodes the packets and writes them to the sound or pattern slots named inside those packets |

From the repository root, configure, build, run tests, then the demo:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j4
ctest --test-dir build --output-on-failure
./build/po32_demo

Optional, but recommended for local development:

./scripts/install-git-hooks.sh

That enables the repo-managed pre-commit hook, which runs clang-format

on staged .c

and .h

files before each commit and validates commit subjects against Conventional Commits. The repo-managed pre-push

hook runs the static analysis script before push.

The demo builds a transfer frame, renders it to audio, decodes it back (verifying a lossless roundtrip), synthesizes a drum hit, and writes two WAV files: demo_modem.wav

and demo_kick.wav

| Command | Purpose | |---|---| ./build/po32_example | Minimal roundtrip: encode, render, decode, and verify | ./build/po32_demo | End-to-end demo: transfer frame build/render/decode plus local drum synthesis | ./build/po32_pattern_editor | Interactive PO-32 pattern editing and WAV export | ./build/po32_decode_capture <input.wav> <out-dir> | Packet and pattern dumps from a transfer WAV |

| Header | Responsibility | |---|---| core/include/po32.h | Transfer builder, packet helpers, renderer, and decoder | core/include/po32_synth.h | Drum synthesizer |

| Document | Purpose | |---|---| | Architecture | How the codec works | | Protocol | Wire format details | | C API | C function reference | | Synth | Synthesizer signal path | | Patch Parameters | The 21 parameters | | Examples | Supported example programs | | Contributing | Local setup, checks, and commit conventions |

| Path | Purpose | |---|---| core/src | Core C implementation | core/include | Public C headers | core/examples | Supported C examples | core/tests | Core test coverage | core/docs | Architecture, protocol, and API notes | bindings | Language bindings |

See CONTRIBUTING.md for local setup, verification commands, and the Conventional Commits policy used for SemVer-friendly history.

Source: Hacker News