PM_K‑1 Kit

Everything is wired on the board; this is just what the firmware drives. No breadboarding required.

Component	Raspberry Pi Pico pins
Display — 3.5″ ST7796, 320×480 (SPI0)
SCK / MOSI	GP2 / GP3
CS / DC / RST	GP5 / GP6 / GP7
Touch — GT911 capacitive (I2C0)
SDA / SCL — addr 0x5D	GP8 / GP9
Controls & feedback
PSP joystick X / Y	ADC0 (GP26) / ADC1 (GP27)
Button A (play/stop) / Button B (tap)	GP15 / GP14
WS2812 RGB LED	GP12
Buzzer	GP13

An off‑the‑shelf kit, not a custom board — ballpark one‑off prices (USD).

Part	Qty	~$
Raspberry Pi Pico (or Pico W / Pico 2) — the brain	1	5
52Pi EP‑0172 "Pico Breadboard Kit Plus" — 3.5″ ST7796 cap‑touch, GT911, PSP joystick, WS2812 RGB, buzzer, 2 buttons, breadboard, acrylic panel	1	38
USB cable — power + flashing	1	2
Total (one‑off)		≈ $45

Reference: 52Pi EP‑0172 wiki · vendor code. Lots may ship the screen as ST7796 (320×480) — this build targets that.

Download main.py ↓ Source + README ↗

Two separate steps — and main.py is not a drag‑and‑drop file. The RPI‑RP2 drive only accepts a .uf2 firmware file; a .py copied there is discarded on reboot. You drag‑and‑drop the firmware once, then copy main.py over USB serial.

1. Install MicroPython (drag‑and‑drop, one time): hold BOOTSEL, plug the Pico into USB, and drop the MicroPython .uf2 onto the RPI‑RP2 drive (Pico / Pico 2). It reboots on its own and the drive disappears — that's correct.
2. Copy main.py (the Pico is no longer a USB drive, so use a serial tool): in Thonny pick the interpreter MicroPython (Raspberry Pi Pico), then File ▸ Save as ▸ Raspberry Pi Pico as main.py; or mpremote cp main.py :main.py.
3. Reset — it boots straight into the metronome.
4. Add your own grooves by pasting program strings from the editor into the PROGRAMS list at the top of main.py. If colours, touch, or the joystick look off, flip a flag in the CONFIG block (see the README's calibration notes).

It's one self‑contained file — the ST7796 driver, GT911 touch, WS2812 RGB, buzzer and the polymeter engine, no external libraries.

An alternative firmware that turns the Pico into a self‑contained appliance: it mounts as a USB drive carrying the firmware, your tracks and an offline copy of this editor; drives a full lanes/pads touchscreen; logs your practice to history.json on the device; takes new set lists pushed from the editor over USB‑MIDI; and plays out your computer's speakers over USB‑MIDI. By default the firmware owns the drive (read‑only to the computer — so it can log and can't be accidentally erased); hold button A at power‑on for editor mode (drive writable). The MicroPython firmware above stays the simple, rock‑solid option.

Download CircuitPython bundle ↓ Source + README ↗

1. Flash CircuitPython (raspberry_pi_pico) via BOOTSEL, unzip the bundle onto CIRCUITPY, and power‑cycle. It boots into appliance mode.
2. Program it from the web: build a set list in the editor (Chrome/Edge/Firefox), then the set‑list ⋯ menu → 📟 Save to device. It's pushed over USB‑MIDI and the device shows Saved ✓. (Fallback for any browser: it downloads programs.json — boot holding A and drag it on.)
3. Play through your computer: click 🎹 Device audio, then press play on the device — the full groove sounds through your speakers over USB‑MIDI, in sync; the screen shows a MIDI badge and the buzzer mutes.
4. Practice log: plays over 5 s appear at the bottom of the screen (time · BPM · duration · track); tap a row twice to delete.
5. Firmware updates: ⋯ menu → ⬆ Update firmware — it checks your version, pushes the latest over USB‑MIDI, and the device A/B‑updates with automatic rollback if a build won't boot.