Opus 2.0 beta 2 (build 2)

Opus 2 is a firmware mod for the original Teenage Engineering OP-1 on firmware #246 (not the OP-1 field). Its
small core loads plugins: .opmod files you copy into a mods folder on the OP-1's USB disk. Every feature is a
plugin, so you pick the mods and swap them as files, with no reflashing.

Beta 2: sequencers through the bridge, lighter audio, and fixes from the first week. Still a beta: it has run in
an emulator with the OP-1's own firmware and on my own OP-1. Back up your tape, synth and drum folders first.

Get it

1. The core. Make the update on https://opus-op1.pages.dev/patcher/ from your own copy of TE's
   op1_246.op1. It runs in your browser and nothing is uploaded. Install it through the OP-1's update mode: switch
   it off, hold COM while switching it on, press 1, copy the file onto the "OP-1" disk and eject it. Never choose 7
   or 8 there, they erase your sounds and tape.
2. The plugins. Download opus2-starter-pack.zip below, put the OP-1 in disk mode (shift + COM, then T3) and drag the
   zip's mods folder onto the disk. It merges with the one there and replaces the plugins that changed. Or take
   only the .opmod files you want. Then eject the disk on your computer (the OP-1 leaves disk mode): they load at the next start.
3. Coming from op1r or Hundekraft? Add bridge.opmod too (below).

From beta 1: the same steps. Make the new file (the old one is beta 1's), install it, then drag the new pack's
mods folder onto the disk, and the new bridge.opmod if you use it. Your sounds, presets and tape stay.

Target	the original OP-1, firmware #246 only
The update	op1_246_opus2.op1, 13,150,681 bytes
Its SHA-256	763fb0a463024eb24a70b5039979d6280a7a59c6b070cf3088aa513aa19bd0af
Made from	TE's op1_246.op1, SHA-256 c5315218f825f143b415ca554516541898abee843d3a236df0b54c04e1fb13a9
The starter pack	opus2-starter-pack.zip, 20 plugins, SHA-256 5f9f0a7b07957c630b7c9fa017e55c7561b2e089d323e99086a61b38ad8a3843
The bridge	bridge.opmod 0.8.0, SHA-256 9be7d1b0bbf542675f4da355b1b31a73af52929a4c30b440c5212cf109b868e6

Every file's SHA-256 is in SHA256SUMS.txt.

What's new

• Lighter audio. Plugins' audio memory now sits where the screen's updates don't slow it down. With the pack
  installed and nothing playing, the audio load on my OP-1 went from about 36-43 % to about 10 %. Plate and chorus
  rest while nothing reaches them, and plate, chorus, bitcrush and outatime do the same sound in fewer cycles.
• Plate fixed. It lagged or got switched off on the master: its audio was slowed by the screen sharing its
  memory, at times enough for the CPU guard to switch it off. Thanks to Audivit for the report.
• Sequencers through the bridge (bridge 0.8.0): op1r's chord, dots, euclid, grids, oracle and peal, and
  Hundekraft's c64arp, dots, euclid, oracle and peal, as new rows in the OP-1's sequencer list (shift + the
  sequencer key), each with its own page. Their patterns are saved, and left / right move the keyboard's octave as
  on the stock sequencers.
• FN + blue push switches Fx overdrive's second effect on an effect page where the effect itself takes the blue
  push, such as a bridged one. Thanks to EmergingStates for the report.
• Engine pages follow the LFO in every value they show, as the OP-1's own screens do.
• An incompatible preset (a sound whose engine isn't installed) is refused again, with "needs" and the engine's
  name. Since beta 1 it loaded as iter.
• The diagnostics' task manager no longer counts the plugins' work twice under "opus core".
• For plugin authors: core 2.8 runs plugin sequencers, keeps a page's still part (opus_page_still) and gives
  audio buffers memory of their own (opus_alloc_audio). A page's art may be up to 128 KB. The
  plugin kit's docs are updated.

New plugin versions: amp 1.0.5, bitcrush 2.0.1, chorus 2.0.2, dx 0.4.0, outatime 1.1.3, Fx overdrive 2.0.1, plate
2.0.4, scales and chords 1.1.0, the bridge 0.8.0. The others are as in beta 1. Every plugin with its keys, CPU and
memory: https://opus-op1.pages.dev

Known issues

• With a colour theme, the dim edges of text in a colour other than green can look green on the OP-1's screen. TE's
  own screens show it too: it's the panel, not Opus.
• With USB plugged in, holding Stop at power-on makes the logo take longer.
• In the bridge: swapping effects between bridged plugins can stop the OP-1 as you leave the effect list, and a
  colour theme misses some shades on bridged plugins' pages.

The bridge (alpha)

bridge.opmod is a download of its own, not part of the starter pack. It runs op1r's synth engines, effects and
sequencers (.op1p) and Hundekraft's (.knl) on Opus as they are, with their own screens and pages, and sounds saved
with them play. Put new plugin files in the disk's mods/bridge folder. The bridge's settings list every file it
found, what loaded and why a file didn't. Where both firmwares have a sequencer of the same name, the first file
loads.

It's an unstable alpha, expect bugs. Opus's own plugins run much better on Opus 2, since they're made for its
core, while a bridged plugin runs through a layer that stands in for its own firmware. Porting a plugin to Opus 2's
format is the way to go. Not bridged yet: LFOs (Hundekraft's quad) and other features, drum and sampler engines, and
engines that play samples.

op1r is by popcorp and Hundekraft's firmware by Hundekraft. Every bridged plugin stays its author's work.

Going back

te-boot, the OP-1's own updater and recovery, is never touched, so the way back is always there.

• To stock or another firmware: Opus's menu, T1 (system), the cleaner: turn green to "at restart", then
  switch the OP-1 off and on. Then install the other firmware through update mode as above (stock is TE's
  op1_246.op1). The cleaner keeps a copy of everything it changes, so installing Opus again brings it all back.
• To Opus 1: no cleaner needed, just install it.
• If the OP-1 stops at a black screen with white text: your data is fine. Hold COM while switching on and install
  Opus or your old firmware again. If a plugin is the cause, hold Stop while switching on and delete it from the
  mods folder.

Make your own

The plugin kit is in this repo, in plugin-kit/: guides,
the API reference, the SDK headers, the build tool, four example plugins (bitcrush, zoom, halloween and outatime)
and instructions an AI agent can follow, all GPL-3.0. Plugin ideas are welcome in
Discussions.

Licence

The plugins are © LizardMan, free to use and share. Their source is not published yet, apart from the plugin kit's
four examples (GPL-3.0). dx contains code derived from Google's Music Synthesizer for Android (Apache License 2.0):
its LICENSE and NOTICE are in the zip's licenses/opus.dx/ folder. The core's update file and the patcher's data
are all rights reserved: please don't share them, link to the site instead.

Opus is an independent project and is not affiliated with, endorsed by or supported by Teenage Engineering. OP-1 is
a trademark of Teenage Engineering AB. Modifying firmware is at your own risk.

Found a bug? Report it here, with your build
(hold help on Opus's menu) and the plugins in your mods folder.