RPi Pico のMixer

Play a Wave File

You can use any supported wave file you like. CircuitPython supports mono or stereo, at 22 KHz sample rate (or less) and 16-bit WAV format. The M0 boards support ONLY MONO. The reason for mono is that there's only one analog output on those boards! The M4 boards support stereo as they have two outputs. The 22 KHz or less because the circuitpython can't handle more data than that (and also it will not sound much better) and the DAC output is 10-bit so anything over 16-bit will just take up room without better quality.

Since the WAV file must fit on the CircuitPython file system, it must be under 2 MB.

sox in/sample.wav -r 1600 -c 1 -e signed-integer out/sample.wav

$ soxi sample.wav
Input File     : 'sample.wav'
Channels       : 1
Sample Rate    : 16000
Precision      : 16-bit
Duration       : 00:00:08.00 = 128000 samples ~ 600 CDDA sectors
File Size      : 256k
Bit Rate       : 256k
Sample Encoding: 16-bit Signed Integer PCM

cp sample.wav nya.wav /Volumes/CIRCUITPY

from pmk import PMK
from pmk.platform.rgbkeypadbase import RGBKeypadBase as Hardware  # for Pico RGB Keypad Base
import board

try:
    from audioio import AudioOut
except ImportError:
    try:
        from audiopwmio import PWMAudioOut as AudioOut
    except ImportError:
        pass  # not always supported by every board!
import audiocore
import audiomixer
import digitalio
import array
import time

class KeypadSampler:
    def __init__(self):
        # Set up Keybow
        self.keybow_ = PMK(Hardware())
        self.keys_ = self.keybow_.keys

        self.setup_keypad()
        self.setup_mixer()

    def playing(self):
        return self.audio_.playing

    def setup_keypad(self):
        # The colour to set the keys when pressed.
        rgb = (0, 255, 50)

        # Loop through keys and attach decorators.
        for key in self.keys_:
            # If pressed, send a MIDI note on command and light key.
            @self.keybow_.on_press(key)
            def press_handler(key):
                key.set_led(*rgb)
                print("KEY {}".format(key.number))
                self.play_drum()

            # If released, send a MIDI note off command and turn off LED.
            @self.keybow_.on_release(key)
            def release_handler(key):
                key.set_led(0, 0, 0)

    def setup_mixer(self):
        self.button_ = digitalio.DigitalInOut(board.GP0)
        self.button_.switch_to_input(pull=digitalio.Pull.UP)

        self.audio_ = AudioOut(board.A0)
        self.music_ = audiocore.WaveFile(open("kahana.wav", "rb"))
        print(self.music_)
        self.drum_ = audiocore.WaveFile(open("nya.wav", "rb"))
        print(self.drum_)
        self.mixer_ = audiomixer.Mixer(
            voice_count=2,
            sample_rate=16000,
            channel_count=1,
            bits_per_sample=16,
            samples_signed=True,
        )

        print("start mixer")
        self.audio_.play(self.mixer_)
        self.mixer_.voice[0].play(self.music_)

    def play_drum(self):
        self.mixer_.voice[1].play(self.drum_)

    def update(self):
        self.keybow_.update()

ks = KeypadSampler()

while ks.playing():
    ks.update()

print("stopped")