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metronome/pico-explorer
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Me Here c625a8aaa2 Firmware push fix on both Kit (0.0.24) + Explorer (0.0.4) 
Diagnosed from the user's console output - 25 chunks pushed cleanly at
~124ms each, then stalled. Two coupled causes:

1) Bus contention. tick() and Live sync share self.midi with the chunk
   ACKs. While the device was processing a chunk, a Note On / Clock Out /
   Live-sync FULL heartbeat could land on the same MIDI OUT stream and
   the host's parser dropped the interleaved ACK SysEx.

   Fix: self._fw_pushing flag set on 0x21 BEGIN, cleared on 0x23 COMMIT
   or any error. midi_send / Clock Out / _sync_broadcast / _sync_broadcast_full
   all early-out when _fw_pushing is True. Only ACKs go out during a push.

2) SysEx assembler garbage. self._sx = bytearray() per chunk leaks ~70
   bytes / chunk that only GC'd every 50 chunks. 25 chunks of trash plus a
   slow heap walked the wrong way explains the ramp-up to 174 -> 119 -> 124
   ms ACK times. GC every chunk now (~30ms cost on RP2040/RP2350 with
   small heap) so the assembler buffer is always fresh.

Same patch on both pico-cp/ and pico-explorer/ since the bug is identical.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-30 22:51:46 -05:00
..
app.py Firmware push fix on both Kit (0.0.24) + Explorer (0.0.4) 2026-05-30 22:51:46 -05:00
boot.py PM_X-1 0.0.1: Pimoroni Explorer sibling firmware + Kit 0.0.23 device-id reply 2026-05-30 20:43:38 -05:00
code.py PM_X-1 0.0.1: Pimoroni Explorer sibling firmware + Kit 0.0.23 device-id reply 2026-05-30 20:43:38 -05:00
programs.json PM_X-1 0.0.1: Pimoroni Explorer sibling firmware + Kit 0.0.23 device-id reply 2026-05-30 20:43:38 -05:00
README.md PM_X-1 0.0.2: portrait flip + Kit-style layout (no more overlapping bits) 2026-05-30 21:37:12 -05:00

README.md

PM_X-1 "Explorer" — CircuitPython edition (Pimoroni Explorer · RP2350)

The CircuitPython firmware for the Pimoroni Explorer Kit (PIM744), set up as a self-contained appliance. Sibling to the PM_K-1 build in ../pico-cp/ (the 52Pi EP-0172 kit) — same engine, same program strings, same programs.json, same web editor.

This board is a 2.8″ ST7789V LCD + 6 user buttons + piezo speaker built around an RP2350B (Pico 2 class chip). No touchscreen, no joystick, no RGB LED. Editing is done in the web editor with Live sync on; the device mirrors changes in real time and emits its own play/stop/bpm/sel deltas back.

Hold the device in portrait with the A/B/C buttons along the top and X/Y/Z along the bottom. The firmware drives the LCD as a 240 × 320 portrait at display.rotation = 270 — same UI shape as the PM_K-1 Kit, just shorter. If the screen comes up upside-down on your unit, change DISPLAY_ROTATION near the top of app.py to 90 (or 180 if rotated 180°) and re-flash.

Controls

Button Action
A play / stop
B tap tempo
C menu (Settings / Help / About / Practice log)
X prev track (hold to repeat)
Y tempo −1 (hold to repeat; after ~1.5 s the step grows to −5)
Z next track (hold to repeat)
X + Z tempo +1 (chord; same hold-repeat as Y)

In a menu: X / Z move the cursor up / down, Y decrements the focused value, A commits or cycles, B = back, C = close.

Install

  1. Flash CircuitPython for Pico 2 / RP2350. Hold BOOTSEL on the Explorer, plug it in over USB-C, drop the Pimoroni Explorer (RP2350) CircuitPython .uf2 onto the RP2350 drive. A CIRCUITPY drive appears.
  2. Copy the bundle onto CIRCUITPY — boot.py, code.py, app.mpy, programs.json, font_s.bin / font_m.bin / font_l.bin, logo.bin / midi.bin / usb.bin, editor.html (offline editor). If an old app.py is on the drive, delete it.
  3. Power-cycle. It boots into appliance mode and runs.

Program it from the web

Open https://metronome.varasys.io in Chrome / Edge / Firefox. The set-list ⋯ menu → 📟 Save to device pushes a programs.json over USB-MIDI; the device persists it and reloads. Click 🔗 Live sync to mirror edits in real time.

Pin reference

The display, buttons, and audio are wired into the board — no jumpers required. CircuitPython's official board definition for pimoroni_explorer2350 exposes board.DISPLAY pre-initialized, so the firmware just uses it.

Function GPIO
Button A GP16
Button B GP15
Button C GP14
Button X GP17
Button Y GP18
Button Z GP19
Piezo audio (PWM) GP12
Piezo amp enable GP13
I²C SDA (QwSTEMMA) GP20
I²C SCL (QwSTEMMA) GP21
Display board.DISPLAY (8080 parallel bus on GP26..GP39, initialized by board.c)

Calibration (flags at the top of app.py)

  • Speaker too loud / quiet: the piezo + amp gain is fixed in hardware. MUTE_SPEAKER silences the click; SPEAKER_AUTO_MUTE auto-mutes when a MIDI host is listening.
  • Buttons feel inverted: the polarity is hard-coded to active-low (pull-up). If a button fires on release instead of press, check the BTN_* pin map at the top of app.py.
  • Display orientation: the board's CircuitPython init mounts the panel landscape (320 × 240). If your screen looks rotated, that's a board.c-level thing — file a CircuitPython bug, don't patch the firmware.

If app.py ever errors, CircuitPython prints the traceback on the screen and over USB serial — send me that.