A 4-track eurorack step sequencer built around polymetric randomization — each track has independent gate, pitch, velocity and mod subtracks with their own lengths and clock dividers, and a randomizer that regenerates a whole track or a single layer at the press of a button. It replaces a live setup of four sequencers plus utility modules with one hands-on module.
▶ Try it live — the browser preview is the real faceplate layout; everything works with mouse or touch. See the manual for how to play it.
The firmware, engine, and web preview are working and tested — but I'm a software developer, not a hardware engineer, and this design is about to go to manufacturing. I'd be grateful for experienced eyes on the electronics before I order boards.
The module is a three-board stack behind a eurorack faceplate:
- Control board — buttons, encoders, jacks, LED drivers, shift registers, USB-C, SD card, MIDI in.
- Main board — RP2350 (PGA2350), DAC8568 CV outputs with op-amp output stages (1V/oct), eurorack power entry and regulators.
- Board-to-board via 2×16 shrouded headers.
Review materials:
- 📄 Schematic review PDFs (one page per subcircuit, net-label style) and the full KiCad projects, gerbers, and STEP files are attached to the latest GitHub Release.
- The design source is atopile (
hardware/boards/elec/src/), compiled to KiCad — the PDFs and KiCad files are what you want to look at if you don't read.ato.
Particularly unsure about: power entry & regulation, the DAC output stage (1V/oct scaling/offset accuracy), the board-to-board pinout, and the USB-C / SD / MIDI input circuits. Issues and PRs welcome.
- 4 tracks × 4 subtracks (gate / pitch / velocity / mod), each with independent step length (1–64) and clock divider — polymetric by default.
- Randomizer with per-track scale, root, range, density and velocity config; four gate algorithms (RAND / EUCL / SYNC / CLST); 8 factory presets plus user presets.
- Drift (per-subtrack stochastic mutation) and per-track transpose with scale quantization.
- Free output routing: any subtrack to any of the 4 output jacks.
- Internal, MIDI, or external clock; per-output MIDI channels.
Full documentation: docs/manual.md (also built into the web app — the MANUAL button).
| Part | What it is |
|---|---|
crates/engine |
no_std pure Rust sequencer logic (runs in WASM and on the RP2350) |
crates/renderer |
no_std display rendering via embedded-graphics |
crates/web |
WASM bindings + Canvas2D target for the browser |
crates/firmware |
RP2350 firmware: SPI display, DACs, buttons/encoders |
web/ |
TypeScript preview: Tone.js audio, Web MIDI, canvas faceplate UI |
hardware/ |
atopile PCB projects (control + main + faceplate) and the build pipeline |
make dev # Vite dev server (builds WASM first)
make test # All tests: Rust + web + hardware scripts
make rust # Test + lint + build firmware
make web # Test + lint + build web bundle
make hardware # Full hardware pipeline (KiCad + FreeRouting required)- Code: MIT
- Hardware design (
hardware/): CERN-OHL-S v2 — strongly reciprocal open hardware licence.