I2S and sound

Introduction

In order to play audio files we need:

the audio file itself, which we expect to be in uncompressed wav format
a file system from which to read the file. This is available in MicroPython either in its internal flash or on an SD card
a fast 16 bit DAC to convert the audio data into an analogue form that can be consumed by a loadspeaker
an amplifier to get enough signal power needed for the loadspeaker
a software driver implementing the I2S protocol

The digital data must be transferred to the DAC, which is done through the I2S protocol

invented by Philips in the end 1980 ies.

There are two cheap I2S boards converting digital audio data to an analogue audio signal and communicating through the I2S protocol:

the ! MAX98357A, a mono converter board with integrated amplifier to which we can directly connect a loadspeaker
the PCM5102a, a stereo converter board with a connector for head phones. If we want to connect a loudspeaker to this board we have to pass through an audio amplifier.

Here is a table showing how I connected the MAX98357A to the ESP32 board:

MAX98357A pin	pin on ESP32 CPU card	signification
Gnd	Gnd
Vcc	3.3V
SD	n.c.
Gain	Gnd	important: don't leave this pin floating!
Din	D2: GPIO 21	audio data
BCLK	D3: GPIO 17	bit clock
LRC (LRCLK)	D1: GPIO 22	left/right clock

Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	max98357a.png	r1	manage	203.5 K	2021-01-24 - 16:23	UliRaich
png	pcm5102.png	r1	manage	127.0 K	2021-01-24 - 16:23	UliRaich
png	pcm5102back.png	r1	manage	88.2 K	2021-01-24 - 17:48	UliRaich

Topic revision: r2 - 2021-01-24 - UliRaich