Control the pad LEDs for the Akai MPD218 over USB MIDI

mpd218.py

"""Reusable LED control for the Akai MPD218 over USB MIDI.

    from mpd218 import pad_on, pad_off, all_on, all_off
    pad_on(13)        # light pad 13
    pad_off(13)
    all_on(); all_off()

Pad indices are 1..16 (bottom-left = 1, top-right = 16, matching the device's default
note mapping of pads 1..16 -> MIDI notes 36..51 on channel 10).
"""
import atexit
import mido

PORT_NAME = 'MPD218 Port A'
CHANNEL = 9              # MIDI channel 10
FIRST_NOTE = 36          # pad 1
NUM_PADS = 16

_out = None

def _port():
    global _out
    if _out is None:
        _out = mido.open_output(PORT_NAME)
        atexit.register(_out.close)
    return _out

def _note(pad):
    if not 1 <= pad <= NUM_PADS:
        raise ValueError(f"pad must be 1..{NUM_PADS}, got {pad}")
    return FIRST_NOTE + pad - 1

def pad_on(pad):
    _port().send(mido.Message('note_on', channel=CHANNEL, note=_note(pad), velocity=127))

def pad_off(pad):
    _port().send(mido.Message('note_off', channel=CHANNEL, note=_note(pad), velocity=0))

def all_on():
    p = _port()
    for pad in range(1, NUM_PADS + 1):
        p.send(mido.Message('note_on', channel=CHANNEL, note=_note(pad), velocity=127))

def all_off():
    p = _port()
    p.send(mido.Message('control_change', channel=CHANNEL, control=123, value=0))
    for pad in range(1, NUM_PADS + 1):
        p.send(mido.Message('note_off', channel=CHANNEL, note=_note(pad), velocity=0))


if __name__ == '__main__':
    import time
    print("Self-test: sweep, all-on, all-off.")
    for pad in range(1, NUM_PADS + 1):
        pad_on(pad); time.sleep(0.1); pad_off(pad)
    time.sleep(0.3)
    all_on(); time.sleep(0.8); all_off()