# PM_K‑1 "Kit" — CircuitPython edition (USB drive + editor)

The **CircuitPython** firmware for the 52Pi EP‑0172 Pico kit. Unlike the MicroPython version
(`../pico/main.py`), this makes the Pico mount as a **USB drive (`CIRCUITPY`)** that carries the
firmware and your tracks — so you can edit on the web and reprogram it without Thonny. It runs the
same program‑string language as <https://metronome.varasys.io>.

> **Status: experimental, phase 1.** This drives the screen/touch/joystick/buzzer and reads your
> grooves from `programs.json`. The editor's one‑click "Save to device" and USB‑MIDI audio‑to‑computer
> are landing in later phases. The simpler **MicroPython** firmware (`../pico/main.py`) remains the
> rock‑solid fallback — and the Pico can't be bricked (BOOTSEL → drag a MicroPython `.uf2` back).

## Install

1. **Flash CircuitPython:** hold **BOOTSEL**, plug in, and drop the CircuitPython `.uf2` for your board
   onto the `RPI‑RP2` drive (<https://circuitpython.org/board/raspberry_pi_pico/> — or the Pico 2 / W
   build). It reboots and a **`CIRCUITPY`** drive appears.
2. **Copy everything from the bundle** onto `CIRCUITPY` (drag‑and‑drop — it's a normal drive now):
   - `code.py`  (this firmware — runs on boot)
   - `programs.json`  (your grooves)
   - `font_m.bin`, `font_l.bin`  (the anti‑aliased fonts — kept as files to save RAM)
3. It starts immediately. Editing `programs.json` (or re‑saving it from the editor) makes CircuitPython
   **auto‑reload** with the new tracks.

## Controls (same as the MicroPython build)

- **Touch:** on‑screen `◀◀ / ▶ / ▶▶` (prev · play/stop · next) and `− / TAP / +`.
- **Joystick:** up/down = tempo, left/right = previous/next groove.
- **Button A (GP15)** play/stop · **Button B (GP14)** tap tempo.
- **RGB LED** flashes each beat; **buzzer** clicks (accent/normal/ghost).

## programs.json

```json
{ "title": "PolyMeter",
  "programs": [ { "name": "Four on the floor", "prog": "t120;kick:4;snare:4=.x.x;hatClosed:4/2" } ] }
```

Each `prog` is a program string from the web editor. Add/replace entries and save — the device reloads.

## Calibration (flip flags at the top of `code.py`)

- **Red/blue swapped:** flip `MADCTL` between `0x48` (default) and `0x40`.
- **Colours look negative:** toggle `INVERT_COLORS`.
- **Taps land wrong:** set `TOUCH_DEBUG = True`, watch the serial output, then set
  `TOUCH_SWAP_XY` / `TOUCH_INVERT_X` / `TOUCH_INVERT_Y`.
- **Joystick reversed:** toggle `JOY_INVERT_X` / `JOY_INVERT_Y`.
- **Screen blank / garbled:** the panel lot may differ; drop `SPI_BAUD`, and if it's a 240×320 ILI9341
  instead of the 320×480 ST7796, the init/size need changing (this targets the 320×480 you have).
- **RGB LED** is driven by the core `neopixel_write` module — no library to install. If it stays dark,
  your CircuitPython build is unusually missing that module (everything else still works).

If `code.py` ever errors, CircuitPython prints the traceback **on the screen and over USB serial** —
copy that to me and I'll fix it.

The fonts are the same baked anti‑aliased blobs as the MicroPython build (see `../pico/gen_font.py`).