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assimil8or-extended-firmware

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Unofficial extended firmware for the Rossum Electro-Music Assimil8or

assimil8or-extended-firmware is custom firmware for the Rossum Electro-Music Assimil8or, by @brandon-tallent. Open source under MIT, latest release v1.2.2 (October 2026), 8 stars on GitHub.

forRossum Electro-Music Assimil8or·by@brandon-tallent

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MIT· brandon-tallent/assimil8or-extended-firmware·brandon-tallent.github.io/assimil8or-extended-firmware/·downloads come from the creator’s GitHub releases

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13 commits and 6 releases in the last year
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Assimil8or firmware - Tallent Edition

An unofficial firmware extension for the Rossum Electro-Music Assimil8or:

  • A three-band EQ and high-pass filter on every channel, with an EQ of its own for any zone and CV control of every band.
  • A multimode filter on every channel, or on any zone alone: low-pass, band-pass, high-pass and notch at 12 or 24 dB per octave, band stop and a dual low-pass/band-pass, with resonance and CV control of cutoff, resonance, the type's extra setting and the type.
  • Grain mode: a channel or stereo pair plays its sample as up to eight overlapping grains, for stretching, freezing and scattering, with CV control of eight parameters.
  • Time Lock: change a drum loop's pitch without changing its timing. The tempo source is set per channel: the loop's own tempo, a percentage of it, MIDI clock or a CV clock. Channels 2–8 can use channel 1's setting.
  • Compressors: one on every channel and one on the mix outputs, with drive, makeup gain, parallel mix and a sidechain from another channel or the Sample input.
  • Reverb and delay sends on the mix outputs: reverb, gated reverb and chorus algorithms modeled on the Roland DEP-5, and a ping-pong delay synced to MIDI clock or a channel's Time Lock tempo, with low and high cut on every repeat. Sends and effect settings take CV.
  • Resample: record a channel's own output straight into one of its zones.
  • Presets keep the EQ, filter, grain, Time Lock, compressor and effect settings, in files Rossum's software still loads.
  • MIDI remote control (with a Locutus): read and edit presets, browse the card, audition and assign samples, drive the panel and read the display. The protocol is documented so anyone can write an editor.

All original features remain. The new pages sit behind a second press of the Mutate, Pitch, Envelope, Phase Mod and Pan/Mix buttons, and Rossum's software can be loaded again at any time.

See the New Features Guide for how everything works.

Installing

Open the firmware patcher

  1. Download Assimil8or software v3.04 (app-v304-260610.zip) from the Downloads section of Rossum's Assimil8or page. There is no need to unzip it.
  2. Open the patcher above and select that zip. assimil8or-tallent-edition-<version>.zip downloads automatically.
  3. Unzip it and copy both files, app and ext-….bin, to the top level of your micro SD card.
  4. With the card in the front panel slot, use Utilities > Load Software and reboot as for any software update.
  5. Leave the card in. Shortly after the restart the top line of the display reads Extension installed.

Your software file stays in your browser; nothing is uploaded. To use the patcher offline, click Save this tool for offline use on the page, then open the downloaded HTML file in a current browser.

To go back, load Rossum's own app with Utilities > Load Software.

Versions

The patcher shows the version at the top of the page. On the module, go to Utilities > About this Module: the line under SW Rev reads Tallent Edition Rev v1.2.0. A version ending in -dev is a build between releases.

CHANGELOG.md lists the changes in each release. Releases has the patcher for each release.

Each release loads presets saved by earlier releases. A preset saved by a newer release can lose some settings in an older one. The changelog lists these cases.

Writing an editor

PROTOCOL.md is the complete MIDI System Exclusive protocol, with a runnable example. PRESET_FORMAT.md lists the lines this firmware adds to preset files.

Building from source

  • Install the Arm GNU Toolchain (arm-none-eabi-gcc). The published patcher is built with GCC 16.1.0; another version makes a working patch with a build ID of its own.
make
make check

Apply the patch to Rossum's download with both patchers and compare them:

A8_STOCK_APP=/path/to/app-v304-260610.zip make check

Build the patcher page:

A8_STOCK_APP=/path/to/app-v304-260610.zip make release

This writes dist/assimil8or-patcher.html, the patcher page with your build inside it. Open it in a browser and use it as above.

File layout

  • src/ the overlay: C and assembly that replace a reclaimed region of the stock image
  • ext/ the extension image the module loads from the card: the editor commands, grain mode, the Filter page and Time Lock
  • src/stock_abi.ld the stock addresses the code links against; src/patch_layout.json the instructions the patch replaces
  • tools/make_patch.py builds the patch; patcher.py and web/ apply it

License

Our original work is MIT licensed. No rights to Rossum's software are granted by this repository.