4 channel control / 8 note MIDI controller example for Pimoroni RGB Keypad for Raspberry Pi Pico

code.py

# Based on @sandyjmacdonald's original gist:
# https://gist.github.com/sandyjmacdonald/b465377dc11a8c83a8c40d1c9b990a90

import time
import board
import busio
import usb_hid

from adafruit_bus_device.i2c_device import I2CDevice
import adafruit_dotstar

from digitalio import DigitalInOut, Direction, Pull

import adafruit_midi

cs = DigitalInOut(board.GP17)
cs.direction = Direction.OUTPUT
cs.value = 0

# Set up APA102 pixels
num_pixels = 16
pixels = adafruit_dotstar.DotStar(board.GP18, board.GP19, num_pixels, brightness=0.1, auto_write=True)

# Set up I2C for IO expander (addr: 0x20)
i2c = busio.I2C(board.GP5, board.GP4)
device = I2CDevice(i2c, 0x20)

# Function to map 0-255 to position on colour wheel
def colourwheel(pos):
    if pos < 0 or pos > 255:
        return (0, 0, 0)
    if pos < 85:
        return (255 - pos * 3, pos * 3, 0)
    if pos < 170:
        pos -= 85
        return (0, 255 - pos * 3, pos * 3)
    pos -= 170
    return (pos * 3, 0, 255 - pos * 3)


# Read button states from the I2C IO expander on the keypad
def read_button_states(x, y):
    pressed = [0] * 16
    with device:
        # Read from IO expander, 2 bytes (8 bits) correspond to the 16 buttons
        device.write(bytes([0x0]))
        result = bytearray(2)
        device.readinto(result)
        b = result[0] | result[1] << 8

        # Loop through the buttons
        for i in range(x, y):
            if not (1 << i) & b:
                pressed[i] = 1
            else:
                pressed[i] = 0
    return pressed
import usb_midi
from adafruit_midi.note_off import NoteOff
from adafruit_midi.note_on import NoteOn
from adafruit_midi.control_change import ControlChange

print("Midi test")
midi = adafruit_midi.MIDI(midi_out=usb_midi.ports[1], out_channel=0)
print("Default output channel:", midi.out_channel + 1)

# List to store the button states
held = [-1] * 16

control_vals = [0]*4

def handle_volume(channel, up_key, down_key, pressed):
    if pressed[up_key]:
        pixels[up_key] = colourwheel(up_key * 16)  # Map pixel index to 0-255 range

        if not held[up_key]:
            control_vals[channel] = min(control_vals[channel] + 5, 127)
            midi.send(ControlChange(channel, control_vals[channel]))
        held[up_key] = (held[up_key] + 1) % 10

    else:  # Released state
        if held[up_key] >= 0:
            pixels[up_key] = (0, 0, 0)  # Turn pixel off
            held[up_key] = -1  # Set held state to off

    if pressed[down_key]:
        pixels[down_key] = colourwheel(down_key * 16)  # Map pixel index to 0-255 range

        if not held[down_key]:
            control_vals[channel] = max(control_vals[channel] - 5, 0)
            midi.send(ControlChange(channel, control_vals[channel]))
        held[down_key] = (held[down_key] + 1) % 10

    else:  # Released state
        if held[down_key] >= 0:
            pixels[down_key] = (0, 0, 0)  # Turn pixel off
            held[down_key] = -1  # Set held state to off


# Keep reading button states, setting pixels
while True:
    pressed = read_button_states(0, 16)

    handle_volume(0, 0, 4, pressed)
    handle_volume(1, 1, 5, pressed)
    handle_volume(2, 2, 6, pressed)
    handle_volume(3, 3, 7, pressed)


    for i in range(8,16):
        if pressed[i]:
            pixels[i] = colourwheel(i * 16)  # Map pixel index to 0-255 range

            if not held[i]:
                midi.send(NoteOn(i, 127))
            held[i] = (held[i] + 1) % 30

        else:  # Released state
            if held[i] >= 0:
                midi.send(NoteOff(i, 127))
                pixels[i] = (0, 0, 0)  # Turn pixel off
                held[i] = -1  # Set held state to off
    time.sleep(0.01)