Show incoming MIDI as raining MIDI notes on Neopixel grid / matrix in CircuitPython

midi_visualizer.py

# midi_visualizer.py -- show incoming MIDI as raining MIDI notes on Neopixel grid / matrix
# 31 Aug 2022 - @todbot / Tod Kurt
# inspired by
#   https://www.reddit.com/r/esp32/comments/wwah4v/i_made_a_midi_to_led_interface_with_an_esp32_more/
# uses SmolMIDI from Winterbloom: https://github.com/wntrblm/Winterbloom_SmolMIDI

import time
import board

# libraries installed with circup
import usb_midi
import neopixel
import adafruit_pixel_framebuf

# local libraries in CIRCUITPY
import winterbloom_smolmidi as smolmidi

usb_out = usb_midi.ports[1]
usb_in = usb_midi.ports[0]
usb_midi_in = smolmidi.MidiIn(usb_in)

base_note = 36
play_colors = [0xff0000, 0xff0000, 0x00ffff, 0xffff00, 0xff00ff ]
dim = 35
leds_w = 16
leds_h = 8
leds_num = leds_w * leds_h
leds = neopixel.NeoPixel(board.GP15, leds_num, brightness=0.2, auto_write=False)
leds_framebuf = adafruit_pixel_framebuf.PixelFramebuffer( leds, leds_w, leds_h,
                                                          reverse_x=True, alternating=True)

leds_framebuf.fill(0x000033)
leds_framebuf.display()

playing_notes = []  # which notes are playing

def midi_receive():
    global playing_notes, base_note
    while msg := usb_midi_in.receive():  # get to use walrus operator!
        if msg.type == smolmidi.NOTE_ON:
            note = msg.data[0]
            if base_note == 0: base_note = note
            playing_notes.append( note )
        elif msg.type == smolmidi.NOTE_OFF:
            note = msg.data[0]
            try:
                playing_notes.remove( note )
            except ValueError:  # note already removed
                pass

def display_notes():
    # copy old notes to new line
    leds_framebuf.scroll(0,1)

    # display new notes
    for n in playing_notes:
        nn = (n % 12)  + 4 #
        noct = ((n-base_note) // 12) % len(play_colors)
        play_color = play_colors[noct]
        leds_framebuf.pixel(nn, 0, play_color)

    # dim all LEDs
    for y in range(leds_h):
        for x in range(leds_w):
            c = leds_framebuf.pixel(x,y)  # this returns an int not a tuple
            ca =  (c >> 16) & 255, (c >> 8) & 255, c & 255 # make tuple
            c = (max(ca[0] - dim,0), max(ca[1] - dim,0), max(ca[2] - dim,0)) # dim
            leds_framebuf.pixel(x, y, c)  # put new color back

    leds_framebuf.display()

while True:
    midi_receive()
    display_notes()

Here's a demo video of the above code:

midi_visualizeer.mp4