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Erica Synths Put the Full Firmware of a Drum Machine It Still Sells on GitHub Under GPL-3.0

The LXR-02's complete STM32F765 firmware — voices, FX bus, sequencer, MIDI, SD presets, UI — is now free software, with a trademark carve-out and a build you can run on a laptop.

5 min read

On 20 October 2026 Erica Synths created two repositories on GitHub. By 23 October both held the complete source of the firmware running inside the LXR-02, a desktop drum synthesizer the company is still selling today, and both carry the GNU General Public License version 3.

That combination — a current product, the whole firmware, a licence that grants redistribution — is rarer than the phrase “now open source” usually implies. We checked it rather than taking the announcement at face value.

What is actually in the repositories

Two repos, both created 20 October and last pushed 23 October:

RepositoryLicenceStarsForksLanguage
erica-synths/lxr-desktop-appGPL-3.06312C
erica-synths/lxr-desktop-bootloaderGPL-3.04—C

The first is the firmware itself. Its own README describes the scope plainly: an STM32F765 (Cortex-M7 at 216 MHz) “running the drum voices, FX bus, step sequencer, MIDI (DIN + USB), SD-card preset storage and the LCD/button UI.” The tree contains Core, Drivers, FATFS, Middlewares, USB_DEVICE_MIDI, a linker script (STM32F765VGTX_FLASH.ld), a CMakeLists.txt and CMakePresets.json.

The second repository is the bootloader — the part that reads an update file off the SD card and writes it to flash. Shipping that too is the detail that makes the first repository useful. Without the updater, source for the application is something you can read; with it, something you can install.

There are no releases and no binaries in either repository. This is source, and you are expected to build it.

The licence, and the part the licence does not cover

The README states the boundary before you reach the build instructions:

the firmware source code is free software under the GNU GPL version 3 … The names “Erica Synths” and “LXR” and the LXR hardware are the property of Erica Synths and are not covered by this licence. Building and installing your own firmware is at your own risk: Erica Synths provides no support for self-built or modified firmware.

This is the right way to do it, and it is worth saying why. GPL-3.0 governs copyright in the code. It says nothing about trademarks or hardware designs, and a release that leaves that unstated invites the assumption that it does. Erica Synths has drawn the line explicitly: fork the firmware, publish your fork, sell a product running it if you honour the GPL — but do not call it an LXR, and do not expect the warranty to survive your own build.

The repository also carries a NOTICE.md alongside the licence, for third-party components.

It builds on a laptop, and the instructions are unusually careful

The documentation is not a token README. It specifies CMake 3.21 or newer, Ninja, the Arm GNU Toolchain (arm-none-eabi-gcc, “tested with 14.3.rel1 and 11.3.rel1”) and Python 3 for packing the update file, with per-platform install steps for macOS, Windows and Linux. Then two commands:

cmake --preset release
cmake --build --preset release

That produces LXR_V2_V<version>.img, which you copy to the SD card and install through the built-in updater. No programmer, no JTAG, no opening the box.

One line in there is the mark of somebody who actually watched people fail at this:

Use exactly this --cask gcc-arm-embedded package, the official Arm toolchain. The similarly named brew install arm-none-eabi-gcc does not include the C library the firmware needs, and the build fails with it.

That is a real Homebrew trap, and documenting it saves every Mac user an hour.

Sonic Potions, and where the LXR came from

The LXR line began as the open-source LXR from Sonic Potions, the project of Julian Schmidt (sonic-potions.com) — a DIY drum synth kit whose firmware sources have been on GitHub since 2013. Erica Synths’ LXR-02 is the commercial second generation, developed with Sonic Potions. So the hardware’s lineage was always partly open, and a community had already been working around the edges: brendanclarke/LXR02Open, a port of Sonic Potions LXR 0.37 to the Erica hardware, has existed since 25 May 2026, and there are kit organisers, SD-card file utilities and an Akai Force/MPC plugin recreation.

Here is the part that is easy to miss. The original SonicPotions/LXR repository — created 30 March 2013 by Julian Schmidt, 129 stars, described as “Source files for the LXR drumsynthesizer firmware” — carries no SPDX-identifiable licence. GitHub’s API reports it as NOASSERTION: licence-like text it could not match to a standard licence, and there is no LICENSE file at the repository root. So does sunskiefer/LXR02XXL. Erica Synths’ new release is therefore, in licence terms, cleaner than the open-source project it descends from — an unambiguous GPL-3.0 where the ancestor is a judgement call for your lawyer.

And one more, pointing the other way: erica-synths/diy-eurorack — the company’s 775-star DIY Eurorack repository, its most popular by a wide margin — has no licence at all and has not been pushed since August 2020. The company’s biggest public repository is the one you legally cannot reuse. That is almost certainly inattention rather than policy, and the LXR release shows they now know how to fix it.

What this is worth to somebody who owns one

Concretely: you can change how the voices work. You can add a sequencer mode. You can fix something that annoys you and hand the fix to everyone else with the same box. The 12 forks that appeared within three days of the push suggest people were waiting.

The usual caution applies, and Erica Synths states it themselves — self-built firmware is unsupported, and the updater will happily install something broken. But the escape hatch is the same SD card, and the official .img is still available.

For a company selling a current product, this is a real transfer of capability to the people who bought it. There is no deprecation notice attached and no “legacy” framing. The instrument just became permanently modifiable.

Sources

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