soundcube-firmware/soundcube-i2s-test/soundcube-i2s-test.ino

/*
   I2S bi-directional input and output buffered loopback example
   Released to the Public Domain by Cooper Dalrymple
*/
#include <Wire.h>
#include <I2S.h>
#include "codec.h"

I2S i2s(INPUT_PULLUP);

TLV320AIC3204 codec; 

#define SIZE 16
#define ECHO 192000
int16_t buffer[SIZE];
int16_t buffer2[ECHO];

int16_t volume = 0;
size_t count;
size_t tape_write = 0;

void codec_transmit() {
  for(int i = 0; i < count; i++){
    buffer2[tape_write] = buffer[i];
    tape_write++;
    if(tape_write == ECHO) tape_write = 0;
    
    int tape_read = tape_write + 1;
    if(tape_read < 0) tape_read += ECHO;
    buffer[i] += buffer2[tape_read % ECHO];
  }
  i2s.write((const uint8_t *)&buffer, count * sizeof(int16_t));
}

void codec_receive(){
  count = i2s.read((uint8_t *)&buffer, SIZE * sizeof(int16_t)) * sizeof(uint32_t) / sizeof(int16_t);
  for(int i = 0; i < count; i++){
    buffer[i] *= -1;
  }
}

void setup() {
  i2s.setSysClk(48000);

  Serial.begin(115200);

  delay(2000);

  Wire1.setSDA(2);
  Wire1.setSCL(3);
  Wire1.begin();

  delay(100);

  pinMode(19, OUTPUT); // MCLK enable
  digitalWrite(19, HIGH); // enable MCLK

  pinMode(20, OUTPUT); // CODEC reset
  digitalWrite(20, HIGH);

  codec.begin(&Wire1);

  i2s.onTransmit(codec_transmit);
  i2s.onReceive(codec_receive);

  i2s.setDOUT(15);
  i2s.setDIN(14);
  i2s.setBCLK(16); // Note: LRCLK = BCLK + 1
  i2s.setMCLK(18);
  i2s.setMCLKmult(256); // 12.288.000Hz

  i2s.swapClocks();
  i2s.setBitsPerSample(16);

  i2s.setBuffers(6, SIZE * sizeof(int16_t) / sizeof(uint32_t));

  if(!i2s.begin(48000)){
    Serial.println("I2S error!");
    while(100);
  }

}

int32_t last = 0;
int frame = 0;

void loop() {
  frame++;
  if(frame == 48000) frame = 0;
}