USB(PCM2706) to ESP32 for a PC digital sound system

[alw1746]

This project uses a PCM2706 board that has a USB-to-SPDIF interface but also outputs I2S with a jumper setting. This is perfect for building a digital sound system for a PC. The I2S interface outputs 12MHz on the MCLK pin but it worked with just BCLK,LRCLK,DATA connected to the ESP32. For testing, I wired up the following components:

USB(PCM2706) -> ESP32 -> DAC(PCM5102) -> stereo amplifier

On Windows, the module shows up as Speakers (2 - USB Audio DAC) and music apps like VLC output to it just like a normal soundcard. The only catch is the Windows volume/mute control has no effect, you need to use your amplifier for that. However application-level volume control such as in VLC works as expected. Given the module is a standard USB audio device, it should be supported in Linux as well.

Sketch

/* 
Test a PCM2706 board that has a USB-to-SPDIF interface but also outputs I2S with a jumper setting.
The component connections are:    USB(PCM2706) -> ESP32 -> DAC(PCM5102) -> stereo amplifier
*/
#include "AudioTools.h"

AudioInfo info(48000, 2, 32);
I2SStream in;          //PCM2706 USB-I2S
I2SStream out;         //PCM5102 DAC
StreamCopy copier(out, in);

void setup(void) {
  Serial.begin(115200);
  // change to Warning to improve the quality
  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning); 
 
  // start I2S in
  auto config_in = in.defaultConfig(RX_MODE);
  config_in.copyFrom(info); 
  config_in.i2s_format = I2S_STD_FORMAT;
  config_in.is_master = false;    //ESP32=slave,PCM2706=master
  config_in.port_no = 0;
  config_in.pin_bck = 5;
  config_in.pin_ws = 4;
  config_in.pin_data = 6;
  in.begin(config_in);

  // start I2S out
  auto config_out = out.defaultConfig(TX_MODE);
  config_out.copyFrom(info); 
  config_out.i2s_format = I2S_STD_FORMAT;
  config_out.is_master = true;
  config_out.port_no = 1;
  config_out.pin_bck = 7;
  config_out.pin_ws = 9;
  config_out.pin_data = 8;
  out.begin(config_out);
}

void loop() {
  copier.copy();
}

The PCM2706 board and ESP32-S3 Supermini(Tenstar Robot) are generic Aliexpress items while the PCM5102 is from Adafruit.