EUROPI: A EURORACK MODULE BUILT ON A RASPBERRY PI PICO THAT YOU REPROGRAM YOURSELF
A Eurorack module whose entire behaviour is a MicroPython script you swap from a menu — clock divider tonight, sequencer tomorrow.
AudioOpen-hardware
Built withRaspberry Pi Pico / RP2040
- difficulty
- ●●●○○
- time
- a weekend
- license
- CERN-OHL-S-2.0 (hardware), Apache-2.0 (software), CC0-1.0 (docs)
- repo
- repo ACTIVE583 stars
●●●○○ · a weekend · CERN-OHL-S-2.0 (hardware), Apache-2.0 (software), CC0-1.0 (docs) · 583 stars · repo ACTIVE
WHAT YOU’LL NEED
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COMPAREE VERDICT
EuroPi is a Eurorack module built around a Raspberry Pi Pico whose entire function is a MicroPython script you pick from a menu on the OLED screen. The same hardware can be a clock divider one evening, a sequencer the next, or any of the contributed programs in the library — and you can write your own. The panel has six 0-10 V control voltage outputs, one analogue input, one digital clock input, two knobs and two buttons. The repository is complete: KiCad files, build guides and BOMs for each variant, firmware, calibration procedure, and documentation for every program, and kits are sold by Allen Synthesis. The hardware is CERN OHL-S and the software Apache 2.0, so it is genuinely open, with share-alike terms for modified hardware. Pick your build: the surface-mount version arrives with the small parts already soldered, so you only fit jacks, knobs and the display; the through-hole PCB is all through-hole parts; a community stripboard layout exists too. For someone who already has a modular synth and wants one panel that does six different jobs, this is the project.
IN THE REPO
GOOD TO KNOW
- —Full hardware files (KiCad for the surface-mount version and panel), a community stripboard layout, and a BOM per variant with CPC and Mouser links.
- —MicroPython firmware is pre-compiled; you flash it, then load programs via USB. The repository includes a library of 30+ contributed programs, each with its own documentation.
- —Build guide covers assembly, calibration, and how to add your own programs. There is also a hardware test script.
- —Hardware is CERN OHL-S v2, software Apache 2.0, documentation CC0. Commercial use is allowed, but modified hardware must be shared under the same licence, and modified builds should not carry the Allen Synthesis name.
- —Active repository, maintained since 2021, last updated in September 2026.
- —The surface-mount version needs only basic soldering of panel parts; the through-hole PCB needs more soldering but only through-hole parts.
Parts to buy
6 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Videos
EuroPi Series | What is a EuroPi and why you need (probably more than) one in your rack!
Third-party overview by Modular Exploration. There is no official build video; the repository's written build and calibration guides are the reference.
More builds like this
All projectsGallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the hardware README and decide whether to build the PCB or stripboard version. (Neither PCB needs SMD skills: the surface-mount version comes with the small parts pre-soldered, the through-hole version is all through-hole, and the stripboard layout is community-made and less tested.)
- 2.Order parts from the BOM and either order a PCB or prepare stripboard.(CPC and Mouser links are provided, plus a complete Mouser basket; knobs, the OLED and the power cable come from elsewhere. The panel is a PCB you order with the boards.)
- 3.Assemble the board, flash the firmware, then run the calibration script. (Calibration needs rack power and one patch cable; it makes the 0-10 V outputs and the input readings accurate for your specific components.)
- 4.Load a program from the library via USB and test it in your rack. (Each program has its own documentation explaining what it does and how to use the knobs and buttons.)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- Pick the right variant: the surface-mount PCB comes with the small parts already soldered, the through-hole PCB means soldering every part yourself, and the stripboard layout is community-made and much less tested.
- Skipping calibration works, but your voltages will be slightly off — for pitch CV into an oscillator, run the calibration script first.
- Use the 0.91-inch 128x32 SSD1306 I2C OLED from the BOM: the BOM warns that boards from other suppliers may be too wide to fit, so check the datasheet.
- The front panel is itself a PCB: order the aluminium version from JLC or the black FR4 version from any fab - or buy a panel and PCB kit from Allen Synthesis.
- Outputs are unipolar 0-10 V — modules that expect bipolar CV (for example ±5 V) will need an offset. Read each program's documentation before patching.
- Switching between installed programs happens on the module itself through the menu. Updating firmware or adding your own scripts needs the Pico's USB port; if the module is already running the menu, the '_Bootloader Mode' script puts it into update mode without taking it out of the rack.
Can I use this without writing any code?
Yes. Install the Contrib library once and choose from dozens of user-contributed programs in the module's menu; each has its own documentation. You only write code if you want a function that does not exist yet.
Do I need to know MicroPython?
Not to use existing programs. To write your own, basic Python and some understanding of control voltage will get you most of the way — the firmware handles the DAC, inputs, and UI, so scripts are short.
What is the difference between the PCB and stripboard versions?
There are three: the surface-mount PCB (small parts pre-soldered, easiest), the through-hole PCB (all through-hole parts, the most-built version), and a community stripboard layout that is less tested and not maintained by Allen Synthesis. All share the same schematic and firmware.
Can I sell modules built from this?
Yes, within the licences: the hardware is CERN OHL-S v2 and the software Apache 2.0, so you keep the licence notices and share the source of any hardware changes. If you modified the design, do not sell it under the Allen Synthesis name.
How much power does it draw?
The project does not publish a current-draw figure. It runs from standard plus and minus 12 V Eurorack power through a 10-to-16 pin cable; check the polarity (red stripe is minus 12 V) before powering it.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
The repository's contrib folder holds dozens of user-contributed programs, from sequencers to probability gates to Turing machines. Which one would you load first, and what would you want to build that is not in the library yet?
Allen Synthesis
Allen Synthesis is a UK-based maker who designs open-source Eurorack modules. EuroPi was created to make modular synthesis more accessible by giving people a single module that can take on multiple roles, avoiding the cost and panel space of buying separate dedicated modules.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1mo agoedited
Practical notes from our verification: the repository is well maintained, with the last update in September 2026. The through-hole BOM links each part to CPC and Mouser and offers a complete Mouser shopping basket, which saves the usual hour of cross-referencing. There are three hardware variants: a surface-mount version where the small parts come pre-soldered and you only add the panel components, the through-hole version most people have built, and a community stripboard layout that Allen Synthesis has not tested itself but that others have built successfully. All share the same schematic and firmware. Licensing is split: Apache 2.0 for the software, CERN OHL-S v2 for the hardware and CC0 for the documentation, and the hardware is OSHWA certified. Calibration is optional: skip it and the module uses default values, but run the calibration script with a patch cable if you want accurate voltages, for example for quantized outputs. The best walkthrough is the written build guide; the video we link is a third-party overview from Modular Exploration. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.