FILTRE
A pocket French-touch sampler for the M5Stack Cardputer-ADV + TERM512 lid.
Chop a record onto the keys, sweep one filter, let the 909 kick pump it, arrange
the song and bounce mix + stems to SD. Guide: docs/FILTRE.md.
Study a reference track bar by bar and load its arrangement into the song
page: the arranger.
FILTRE is a fork of Microgroove by lebiro.studio
(MIT), which itself derives parts from
Cardputer-Adv-Tracker by
qwertyuu (MIT). Everything below this line is the upstream Microgroove README,
kept for the instrument it still contains.
Microgroove
A wallet-sized groovebox that turns $30 of hardware and a 3D printer into a four-track acid powerhouse.
Firmware for the M5Stack Cardputer-ADV, by lebiro.studio.
Print it. Flash it. Jam.
What it does
- 3 synth tracks — each switchable between a mono 303-style voice
(saw/square/tri/sine/wavetable → resonant SVF filter, accent and slide)
and 2–3-voice polyphony. Overlapping notes record a slide in mono, a chord in poly.
- 8 drum lanes — each independently 808 synthesis, 909 synthesis, or
SD sample playback; per-lane volume, tune (±12 st), decay, and choke groups
(909 open/closed hats choke by default).
- Live mic sampling — hold one key; the footer becomes a level meter. Release to
auto-trim, write to SD, and play it on a drum lane instantly (max ~2.6 s).
- Resampling — hold SONG while playing to bounce ~1.9 s of the master mix onto any pad.
- Sequencer — 8 patterns × 16 steps, hold-to-clone, bar-quantized pattern switching,
live record with quantize / step-write / hold-to-erase.
- Song mode — 64-slot pattern chain with loop point.
- User wavetables — drop single-cycle WAVs (AKWF) on the card; they appear as oscillators.
- 8 project slots on microSD; sampled sounds reload with projects by filename.
- One key = one function — hold any orange-labeled key 0.5 s for its second function,
with a progress bar so nothing fires by accident. The note keys mirror a real piano layout,
E–F and B–C gaps included.
Full feature tour and guides: docs/USER_MANUAL.md
Get it running
Pick whichever flashing route suits you — all three are on the
Releases page.
Option 1 — pre-built binary: grab microgroove.bin (a merged image) and
flash it to offset 0x0 with esptool
(esptool.py write_flash 0x0 microgroove.bin) or any ESP32-S3 flashing tool.
Option 2 — Arduino IDE (from the release zip): download
Microgroove_source.zip, unzip it (keep the folder named Microgroove), open
Microgroove.ino, install the M5Cardputer library (pulls in M5Unified/M5GFX),
select the M5Cardputer board (or ESP32S3 Dev Module with USB CDC on boot), and
Upload. A HOW_TO_FLASH.txt is included in the zip.
Option 3 — build from source (this repo): clone it and open Microgroove.ino
in the Arduino IDE, or use PlatformIO:
[env:m5stack-cardputer]
platform = [email protected]
board = esp32-s3-devkitc-1
framework = arduino
build_flags = -DESP32S3 -DARDUINO_USB_CDC_ON_BOOT=1 -DARDUINO_USB_MODE=1
lib_deps = M5Cardputer=https://github.com/m5stack/M5Cardputer
Then, for the demo + samples: copy either the release's
Microgroove_SD_card.zip contents or factory-sd/groovebox/ to
the root of a FAT32 microSD. Power on → hold LOAD → tap SONG → PLAY.
No card? Hold LOAD+SAVE together for a built-in demo.
The shell
Print files, keycap label sheet (v6), and assembly guide:
MakerWorld · hardware/
Keys at a glance
T1 T2 T3 TD select tracks (hold = mute) · P1–P8 select patterns (hold = clone) ·
the note keys are a piano (whites on the home row, sharps above, E–F/B–C gaps dead),
and the first eight white keys become pads 1–8 when the drum track is selected.
Orange = the hold (0.5 s) function; green = the sampling holds. AUX held samples
the mic, SONG held while playing resamples the mix. That picture is upstream Microgroove; FILTRE moves
several keys. Hold ok for the current map on the lid, or read the FILTRE guide.
Architecture
Microgroove.ino setup / main loop (core 1: input, sequencer, UI)
audio_engine.cpp render task (core 0), dual buffer -> Speaker.playRaw
synth_voice.h 303-style voice (osc + SVF + envelopes)
sequencer.h/.cpp SynthTrack (1-3 voice alloc), patterns, transport, live record
drum_voice.h 808/909 synthesis + per-lane engine/choke logic
sampler.cpp WAV decode -> 192 KB RAM pool, playback voices
mic_sampler.cpp mic capture + engine resampling -> SD/pool
wavetable.cpp 8 built-in tables + user single-cycle WAVs
storage.cpp GBX v2 project files (loads v1 transparently)
input.cpp keyboard snapshot diffing -> short/long-press dispatch
ui.cpp 5 pages, sprite double-buffered
keymap.h every key assignment in one file
All firmware files live in the repo root next to Microgroove.ino (Arduino
sketch layout) — open the folder in the Arduino IDE and it picks them all up.
22.05 kHz, 256-sample buffers, all voices rendered per-sample into a soft-clipped
mix on core 0. Project files are versioned: v2 stores chords and per-track VOICES;
v1 files load transparently (and become v2 on the next save).
License & lineage
MIT — see LICENSE. The synth voice, 808 drum synthesis, and audio task
architecture are derived from
Cardputer-Adv-Tracker by
qwertyuu (MIT), substantially redesigned into a different instrument. The
factory sample pack is CC0 by lebiro.studio.
If Microgroove earns a place on your desk: Ko-fi ☕
