Play high-quality MP3s on RP2350 Tiny 2350 using the MacroPadSynthPlug as audio interface

mp3-cycler.py

# mp3-cycler.py -- Play high-quality MP3s on RP2350 Tiny 2350
#                      using the MacroPadSynthPlug as audio interface
# 15 Aug 2024 - @todbot / Tod Kurt

import time, os, random
import board
import audiocore, audiopwmio, audiomixer, audiomp3
import busio
import keypad
import rainbowio
import adafruit_rgbled

# Pimoroni Tiny2350 RGB LED has RGB LED on GP18,19,20, active low
led = adafruit_rgbled.RGBLED(board.GP18, board.GP19, board.GP20, invert_pwm=True)
# Pimoroni Tiny2350 BOOT button is on GP23 with external pullup
keys = keypad.Keys( (board.GP23,), value_when_pressed=False, pull=False)

# MacroPadSynthPlug : MIDI input : Tiny 2350 SCL = GP13
uart = busio.UART(rx=board.GP13, baudrate=31250)
# MacroPadSynthPlug : audio output : Tiny 2350 SDA = GP12
audio = audiopwmio.PWMAudioOut(board.GP12)
mixer = audiomixer.Mixer(channel_count=2,voice_count=1,sample_rate=44100, buffer_size=2048)
audio.play(mixer)

# find all the mp3 files in the given directory
mp3_dir = "/mp3"
mp3_paths = []
for fname in sorted(os.listdir(mp3_dir)):
    fname = fname.lower()
    if fname.endswith(".mp3") and not fname.startswith("."):
        fullpath = mp3_dir + "/" + fname
        print('-', fullpath)
        mp3_paths.append(fullpath)

mp3i = 0   # index of which mp3 file to play
mp3 = audiomp3.MP3Decoder(mp3_paths[mp3i])

print("playing...", mp3i, mp3_paths[mp3i])
mixer.voice[0].play(mp3)

while True:
    if mixer.voice[0].playing:
        led.color = rainbowio.colorwheel( time.monotonic() * 400 )
    if key := keys.events.get():
        #print("key:",key)
        if key.pressed:
            mixer.voice[0].stop()
            mp3i = (mp3i + 1) % len(mp3_paths)
            mp3 = audiomp3.MP3Decoder(mp3_paths[mp3i])
            print("now playing:", mp3i, mp3_paths[mp3i])
            mixer.voice[0].play(mp3)
    time.sleep(0.01)