Circus Arrhythmia FM

Circus Arrhythmia FM is a patch for the firmware of the Novation Circuit Rhythm. It corrects bugs and adds functions.

Current release: 0.2.2 (release notes). Project objectives: principles.

Arrhythmia is not affiliated with Novation or Focusrite. Novation and Focusrite do not endorse Arrhythmia.

Install

Before you start, make a backup of the microSD card (procedure).

1. Download the Novation firmware 2.0.1: https://components.novationmusic.com/api/v2/firmwares/169/file.
2. Close Novation Components and all other music applications.
3. Connect the unit to the computer with a USB cable.
4. Open https://llcoolkm.github.io/arrhythmia/web/ in Chrome.
5. Click Connect MIDI.
6. Select the downloaded file.
7. Click Install.
8. When Play flashes on the unit, push Play.

Troubleshooting, other download procedures and the return to stock: install guide.

Bug fixes

• Parameter locks. On the stock firmware, a parameter lock stays active on the next steps until you turn the knob. In Arrhythmia, a step without a lock uses the knob value.
• Sound processor fault. On the stock firmware, the unit can stop when the sound processor does not answer. Arrhythmia limits the wait for an answer. After a timeout, Rec flashes white (procedure).

Functions

The synthesizer functions are in arrhythmia-firmware only.

• FM synthesizer on track 8. A 4-operator FM synthesizer with 4 voices (synth).
• Synth recovery after sample loading. After a pack change or a sample load, the synth starts again automatically (loading samples).
• Sound selection in the Sample view. In the Sample view of track 8, the 16 pads of rows 3 and 4 select one of 16 ratio families. Page 1 uses the serial algorithm. Page 2 uses the dual stack algorithm. A tap selects the sound and plays it. Sample flips select the sound per step (choosing a sound).
• Envelope and tone controls. On track 8, macros 1 to 8 set feedback, attack, decay, sustain, release, FM depth, filter cutoff and resonance. MIDI CC 21 to 28 and parameter locks operate on all eight (macros).
• Synth page. Shift + Track 8 opens the synth page. Page 1 sets chords. Page 2 sets scales, scaled tracks and key. Macros 1 to 4 set tune, modulator attack, modulator decay and modulator floor. A view or track button closes the page and does its normal function. Clear + macro sets the default of that macro (synth page).
• Chords on track 8. Each pad and each sequencer step plays 1 to 4 notes. With 1 note per press and poly on, held pads sound together.
• MIDI polyphony on track 8. MIDI notes on the channel of track 8 play on the synthesizer.
• Scales on tracks 1 to 7. The Note view uses one of eight scales (ten in arrhythmia-devkit) (scales).
• Modules. Small programs on the microSD card control the pads, lights, notes and MIDI. The release has 10 modules: paint, games, a light show and modules that play notes (modules). To write a module, refer to developers.
• Module files over USB. The module files web page writes, replaces and deletes module files on the microSD card without a card reader (add modules with the web page).
• MIDI export. The MIDI export web page converts a project into a ZIP file for a DAW: a multitrack MIDI file, the samples that the project plays and a note map for Drum Racks. It reads a copy of the card or the unit itself over USB (MIDI export).

Limits

• In arrhythmia-firmware, track 8 plays the synthesizer only. It does not play samples.
• The synthesizer has 32 sounds: 16 ratio families under 2 algorithms. It has no presets. The other six pages of the Sample view of track 8 are dark.
• At high pitch, the ratio families fade to a plain tone and sound alike (known issues).
• Sample flips stored on track 8 in older projects and factory patterns change the sound on those steps.
• The synthesizer has a maximum of 4 voices. A note that fades out after its release occupies a voice.
• During a sample load (a pack change, or a sample transfer or load including SysEx read-back), the synth stops and its sounding notes stop. The synth starts again after the load. If the restart fails, the synth is silent until a power cycle (loading samples).
• The synth output is decreased by a fixed amount. Set the balance with the mixer level of track 8 (output level).
• Arrhythmia is not for the Circuit Tracks or for other firmware versions of the Circuit Rhythm.

Two images

If you are not sure, install arrhythmia-firmware.

Rebuild from source: current image and 0.1.1 image.

Requirements

• A Circuit Rhythm with firmware 2.0.1 (build 5706) and bootloader 4799.
• The official firmware file 5706 from Novation.
• Chrome on Windows or Linux, or Python 3.12 on Linux. macOS is not tested.
• A USB cable and a microSD card reader.

Return to stock

Use Back to stock on the installer page, or tools/flash.py on Linux (procedure). Novation Components cannot do this.

Risks

• You install modified firmware at your own risk.
• Make a backup before the installation.
• A very high load can cause audio errors.

Licence

MIT (LICENSE). The licence applies only to the Arrhythmia code and documents. It does not apply to the Novation firmware.

Acknowledgements

CIRCUITS-HACKS-RC by Ghillermo, a community modification for the Circuit Tracks, gave useful information. Arrhythmia is a separate project.