op1r-src

Source code of op1r, custom firmware for the Teenage Engineering OP-1 (firmware R246): custom synth engines and effects with their own screens, quad LFO, euclid and dots sequencers, USB audio track outs, tape markers, count-in, punch in/out, sample editor, resource monitor and more.

Users: you don't need this repository. Patch your firmware with op1r (also in the browser).
Plugin authors (new synths / effects): read synth_sdk/PLUGINS.md. You can write and test a plugin on a PC without any firmware.
Firmware builders: see below.

This repository contains no Teenage Engineering firmware. Building needs your own copy of the official op1_246.op1. The next op1r release (op1r 27) is the first one built from this repository.

Layout

path	content
`synth_sdk/plugins/`	synth engines and effects, one folder each (`plugin.json` + C + screen)
`synth_sdk/template/`	starting points for a new synth / effect
`synth_sdk/op1_plugin.h`	the plugin API
`synth_sdk/dispatcher.c`, `hook.S`, `link.ld`	hooks into the firmware
`synth_sdk/screens/`, `seq/`, `lfo/`, `tape/`	core features (screens, sequencers, quad LFO, tape tools)
`synth_sdk/display/`	SVG generators for the screens
`synth_sdk/harness/`	host tests and renderers (screens to PNG, plugins to WAV)
`synth_sdk/make_firmware.py`	builds the firmware
`tools/`	MIDI / USB test scripts
`toolchain/Dockerfile`	Blackfin cross compiler (bfin-elf gcc 12)

Testing on a PC (no firmware needed)

Requirements: a C compiler, Python 3 with pycairo (screen previews) and numpy (some tests).

cd synth_sdk
python3 harness/audio.py supersaw           # plugin -> harness/out/audio_supersaw.wav
python3 harness/render.py tape out.png      # plugin screen preview
python3 harness/render_euclid.py            # other screens: harness/render_*.py

Building the firmware

Requirements: Docker, Python 3, the original op1_246.op1, and op1repacker.

docker build -t bfin-elf-toolchain toolchain                      # once, takes a while
git clone https://github.com/op1hacks/op1repacker.git
python3 -m venv op1repacker/.venv && op1repacker/.venv/bin/pip install -e op1repacker
cp /path/to/op1_246.op1 . && op1repacker/.venv/bin/op1repacker unpack op1_246.op1    # -> op1_246/
cd synth_sdk && python3 make_firmware.py --opz                    # -> ../op1_246_custom-repacked.op1

The boot screen of a local build shows op1r <n> and the build time. Install it like any OP-1 update (bootloader update mode); the original firmware can always be flashed back. Use at your own risk: a broken build can lock the OP-1 until you flash a working image.

Some code runs from the firmware's encrypted part. Those few patches are precomputed in synth_sdk/l1_patches.json and target a fixed jump table at the start of the code (hook.S, .l1vec). So plugins and most other changes build without them changing. Changing the L1 patch lists themselves needs a maintainer.

License

GPL-3.0-or-later with an additional permission to combine it with the OP-1 firmware: see LICENSE and NOTICE, which also lists the third-party parts (MIT) and what is not covered. Contributions (e.g. plugins) are accepted under the same terms.