play-mono-wav-from-sdcard.py

# The MIT License (MIT)
# Copyright (c) 2020 Mike Teachman
# https://opensource.org/licenses/MIT

# Purpose:
# - read 16-bit audio samples from a mono formatted WAV file on SD card
# - write audio samples to an I2S amplifier or DAC module 
#
# Sample WAV files in wav_files folder:
#   "taunt-16k-16bits-mono.wav"
#   "taunt-16k-16bits-mono-12db.wav" (lower volume version)
#
# Hardware tested:
# - MAX98357A amplifier module (Adafruit I2S 3W Class D Amplifier Breakout)
# - PCM5102 stereo DAC module
#
# The WAV file will play continuously until a keyboard interrupt is detected or
# the ESP32 is reset
  
from machine import I2S
from machine import SDCard
from machine import Pin

#======= USER CONFIGURATION =======
WAV_FILE = 'taunt-16k-16bits-mono-12db.wav'
SAMPLE_RATE_IN_HZ = 16000
#======= USER CONFIGURATION =======

bck_pin = Pin(21) 
ws_pin = Pin(22)  
sdout_pin = Pin(27)

# channelformat settings:
#     mono WAV:  channelformat=I2S.ONLY_LEFT
audio_out = I2S(
    I2S.NUM0, 
    bck=bck_pin, ws=ws_pin, sdout=sdout_pin, 
    standard=I2S.PHILIPS, 
    mode=I2S.MASTER_TX,
    dataformat=I2S.B16, 
    channelformat=I2S.ONLY_LEFT,
    samplerate=SAMPLE_RATE_IN_HZ,
    dmacount=10, dmalen=512)

# configure SD card:
# See [docs](https://docs.micropython.org/en/latest/library/machine.SDCard.html#esp32) for
# recommended pins depending on the chosen slot.
#   slot=2 configures SD card to use the SPI3 controller (VSPI), DMA channel = 2
#   slot=3 configures SD card to use the SPI2 controller (HSPI), DMA channel = 1
sd = SDCard(slot=2, sck=Pin(18), mosi=Pin(23), miso=Pin(19), cs=Pin(5))
uos.mount(sd, "/sd")
wav_file = '/sd/{}'.format(WAV_FILE)
wav = open(wav_file,'rb')

# advance to first byte of Data section in WAV file
pos = wav.seek(44) 

# allocate sample arrays
#   memoryview used to reduce heap allocation in while loop
wav_samples = bytearray(1024)
wav_samples_mv = memoryview(wav_samples)

print('Starting')
# continuously read audio samples from the WAV file 
# and write them to an I2S DAC
while True:
    try:
        num_read = wav.readinto(wav_samples_mv)
        num_written = 0
        # end of WAV file?
        if num_read == 0:
            # advance to first byte of Data section
            pos = wav.seek(44) 
        else:
            # loop until all samples are written to the I2S peripheral
            while num_written < num_read:
                num_written += audio_out.write(wav_samples_mv[num_written:num_read], timeout=0)
    except (KeyboardInterrupt, Exception) as e:
        print('caught exception {} {}'.format(type(e).__name__, e))
        break
    
wav.close()
uos.umount("/sd")
sd.deinit()
audio_out.deinit()
print('Done')