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sqrl-1

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SQRL-1 Firmware for the M-VAVE FM-1

sqrl-1 is custom firmware for the M-VAVE FM-1, by @hed0rah. Open source under GPL-3.0, latest release v1.1.0 (November 2026).

forM-VAVE FM-1·by@hed0rah

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GPL-3.0· hed0rah/sqrl-1·downloads come from the creator’s GitHub releases

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SQRL-1

SQRL-1 is firmware for the M-VAVE FM-1. It is a fork of Felucca, the open firmware for the FM-1 by Leo Kuroshita (Hügelton Instruments), and keeps everything under Felucca's screens: its engines, voices, sequencer, effects, storage and installer. In place of Felucca's UI it has a shell of its own, built around pairs.

You always play a pair: a SOUND, which makes the tone, and a NOTE engine, which decides what notes to play. Both are called nuts. Hold HOME and the octave from C4 to C5 becomes the wheel: a white key picks the SOUND, a black key the NOTE engine. Hold HOME and tap GLO instead to choose the pair with the knobs.

The FM-1's screen with the wheel open: the SOUNDs in a ring, FM6 in front, the NOTE engines below The FM-1's screen playing CHORD: G7 drawn on the circle of fifths

  • SOUND nuts: eight, one on each white key: FM6, LIZARD (draw the wave), SHOCK, DRUMS (the drum kits), MOUTH (SAM-style speech), ANALOG, PHASE and PHYS. Felucca's other engines and databurn's stay in the source and come back in a custom build (On the sidelines).
  • NOTE nuts: KEYS, CHORD (Orchid-style chords with voicings, strum and just tuning), RUDIMENT (eight lanes of steps, each its own length: a beat under DRUMS, notes under any other SOUND), LINES (a second set of lanes, for a line over RUDIMENT's beat), ALIVE (a cellular automaton), TONNETZ (chords that walk the Tonnetz), ENIGMA (loops a phrase and mutates it), S+H (sample and hold), CANON (a round of the notes you play), ACID (a 303-style line) and HARP (chord buttons and a strum plate).
  • Shared effects: a three-head tape echo with wow, saturation and reverse, a reverb with pre-delay, a chorus with ensemble and dimension modes, and a rotating-speaker insert.

The manual

docs/ is the manual: every nut, page and knob, with the FM-1's own screens. Its tables, ranges and screens are generated from the firmware, and the test suite fails if they differ from the build, so they match the firmware they ship with. Start with Getting started.

To print: a deep dive (8 pages) and a cheatsheet (3 pages), also in docs/apollo.

Install

The installer is a web page, databurn.org/sqrl/install, for Chrome or Edge over USB. Each release also attaches its package to the GitHub release page. Installing is at your own risk.

  • Back up first if you have music on the FM-1. Felucca's editor makes a complete backup; SQRL-1 reads it.
  • To go back, download official V15, FM-1.fwsc, from M-VAVE's download page (FM-1, "PC Firmware") and use the installer's Return to official V15. It checks that the file is V15, saves a complete backup of your SQRL-1 music and sounds to the computer, then installs it. This has been tried on a device. M-VAVE's own updater, M-UPGRADE, does not see an FM-1 running SQRL-1; once the FM-1 is back on V15, M-UPGRADE works as it does on stock firmware.
  • If an install is interrupted, press Install again: it is built to resume. An FM-1 that no longer starts at all can be recovered with FM-1-transporter (see Known issues).

Known issues

  • A shared USB ID. SQRL-1 shows up as 1209:0001 (its updater as 1209:0002), pid.codes' test IDs, which Felucca and other test devices use too. A computer can't tell them apart by ID, and Windows keeps the name it first saw for an ID, so a computer that has run Felucca may still list SQRL-1 as "Felucca". SQRL-1's own ID is planned for v1.0.1.
  • Untested recovery. Resuming an interrupted install and recovering with FM-1-transporter have not been tried on a device.
  • One program at a time on the USB port. On Windows, M-UPGRADE can't open the FM-1 while Chrome or Edge holds it. Close the browser before you run M-UPGRADE.
  • Heavy patches can glitch. Eight BOWED METAL voices across three parts, with the inserts and SHAPE on, are estimated to exceed the CPU budget. The FM-1 then drops voices to recover, and you may hear a click or a stutter first.
  • Official V15's own presets. Whether the presets and patterns saved under official V15 survive an install of SQRL-1 has not been checked, and the installer can't back them up.
  • M-VAVE's FM1 Open. M-VAVE's second official firmware keeps its projects and samples in the flash SQRL-1's code uses, so the installer refuses an FM-1 running it. Back up your projects and samples and return to official V15 with M-VAVE's workbench, then install SQRL-1. To go from SQRL-1 to FM1 Open, return to official V15 first; M-VAVE's direct route over SQRL-1 has not been tested.
  • USB audio on macOS has not been tested.
  • TALK is not in this release (see the changelog).

Bugs

Open an issue at github.com/hed0rah/sqrl-1/issues with the version (tap GLO four times for ABOUT) and, for an install problem, the installer's log. CONTRIBUTING.md says what else helps.

Build

FELUCCA_SHELL=1 ./build.sh

BUILDING.md lists what the build needs, and CONTRIBUTING.md explains how the source is laid out and how the tests work. The manual's Making a nut walks through adding an engine.

Licence

SQRL-1 is a modified version of Felucca: databurn forked it from 1.5.6 on 10.12.2026, brought it up to 1.8.0 on 10.31.2026, and has changed it since. Felucca is by Leo Kuroshita (Hügelton Instruments).

SQRL-1 is free software under Felucca's licence, GPL-3.0-only (LICENSE). Some parts keep their own licences: databurn's engines are MIT, FM6's operator core is msfa (Apache-2.0), PHYS ports DaisySP and Rings (MIT), and the art (the squirrel, the marks and Nibs) is CC-BY-SA-4.0. LICENSING.md and LICENSES/ have the details, and the manual's credits list every file whose licence or author differs.

M-VAVE and FM-1 are trademarks of their respective owners. SQRL-1 is not affiliated with or endorsed by M-VAVE or Hügelton Instruments.