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

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.

Contents

• Overview

• Using It With a PO-32

• Getting Started

• Examples

• Public API

• Documentation

• Project Layout

• Contributing

• License

Overview

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

Using It With a PO-32

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

Getting Started

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

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.

Examples

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 Packet and pattern dumps from a transfer WAV

Public API

Header Responsibility

core/include/po32.h Transfer builder, packet helpers, renderer, and decoder

core/include/po32_synth.h Drum synthesizer

Documentation

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

Project Layout

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

Contributing

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

License

Copyright (c) 2026 Eric Lewis. Licensed under the MIT License. See LICENSE.