I am currently working on a program for my Raspberry Pi Pico (CircuitPython) which could make it play songs to a speaker through I2S.

So, I decided to use the Audiomixer built-in module in CircuitPython, which has a gain control.

import board
import audiomp3
import audiobusio
import busio
import sdcardio
import storage
import audiomixer



# Gets SD's pins 
spi = busio.SPI(board.GP10, MOSI = board.GP11, MISO = board.GP12)
cs = board.GP15
sd = sdcardio.SDCard(spi, cs)

# Mount SD card 
vfs = storage.VfsFat(sd)
storage.mount(vfs, '/sd')

# Setup Audio I2S Out 
audio = audiobusio.I2SOut(board.GP16, board.GP17, board.GP18)

# Setup the volume control
mixer = audiomixer.Mixer(voice_count=1, sample_rate=22050, channel_count=1, bits_per_sample=16, samples_signed=True) 


# attaches the mixer to audio play
audio.play(mixer) 



def play_sound(fileName):
    
    mixer.voice[0].level = 0.5  # MP3 file playing at half volume
    music = audiomp3.MP3Decoder(open(f"/sd/{fileName}", "rb"))
    
    mixer.voice[0].play(music, loop=True) # starts the audio
    print(f"playing {fileName}")

    while audio.playing: 
        pass
          
if __name__ == "__main__": 
    while True:

        play_sound("0_1.mp3")
         

The code works perfectly fine when ran. However, when I import the function like this, it doesn’t play anything, and shows no error…

from audioI2S import play_sound

while True:
    play_sound("0_1.mp3")

Thanks in advance for your help !