MicroGroove - DIY Pocketable Groovebox & Sampler

Microgroove turns the $30 M5Stack Cardputer-ADV into a four-track groovebox: three synth tracks (each switchable between a mono 303-style voice with slide & accent, and 3-voice polyphony for chords), eight drum lanes of 808/909 synthesis or sample playback, live mic sampling, and resampling of its own output.

This listing is the shell and keycap label system that makes it playable — the free, open-source firmware lives on GitHub: https://github.com/matoslav/MicroGroove

It fits the M5Stack Cardputer-ADV specifically. The screen, USB-C port, and headphone jack all stay fully accessible after the swap.

Printing

Print with a 0.2 mm nozzle (strongly recommended). A 0.4 mm nozzle works, but the fine label text won't come out clean.

The parts:

• Top + label top — the two-piece face. The label top is multi-color (blue / red / white).
• Keys — the keycaps, also multi-color.
• Bottom — optional.
• Table stand and box with instructions — optional extras.

The label top and keys need a multi-color setup (AMS / multi-material or manual filament swaps). If you only print in one color, you'll still get a working shell, just without the colored labels.

Assembly

Glue the top and the label top together, slide in the keys, and swap the assembly for the original top your Cardputer-ADV came with. Two screws hold it in place — gluing the two face pieces matters because without it the edges lift.

What the firmware does

• Three acid synth voices — saw/square/tri/sine plus 16 wavetables through a resonant 303 filter. Flip any track from mono squelch to 3-voice chords.
• Eight drum lanes — 808 and 909 synthesis or your own samples, side by side. Tune, decay, and choke each one.
• Sample the room — hold one key, watch the level meter, release. It's already playing on a lane.
• Resample yourself — bounce the live mix onto a pad and build the next layer on top.
• Sequence and arrange — 8 patterns of 16 steps, clone with a hold, chain up to 64 into a full song.
• Ready to play out of the box — the SD image on GitHub ships a five-pattern demo track and a CC0 sample pack.