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

I2S i2s(INPUT_PULLUP);

#define SIZE 256
int16_t buffer[SIZE];

void cw(char first, char second){
  Wire1.beginTransmission(0x18);
  Wire1.write(first);
  Wire1.write(second);
  Wire1.endTransmission();
  delay(5);
}

void setup() {
  Serial.begin(115200);

  delay(1000);

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

  delay(1000);

  // GENERAL
  cw(0x00, 0x00);
  cw(0x01, 0x01);
  cw(0x1b, 0x10); // select I2S

  // ADC
  cw(0x00, 0x00); // select page 0
  //cw(0x01, 0x01); // soft reset
  cw(0x12, 0x87); // NADC 7
  cw(0x13, 0x82); // MADC 2
  cw(0x14, 0x80); // OSR ADC 128
  cw(0x3d, 0x01); // ADC PRB_R1
  
  cw(0x00, 0x01); // select page 1
  cw(0x01, 0x08); // disable crude AVdd
  cw(0x02, 0x01); // enable internal AVdd LDO
  cw(0x0a, 0x0B); // set input CM to 0.9V and LO to 1.65V
  cw(0x3d, 0x00); // ADC PTM_R4
  cw(0x34, 0x80); // route IN1L to LEFT_P with 20k input impedance
  cw(0x36, 0x80); // route CM to LEFT_M with 20k input impedance
  cw(0x37, 0x80); // route IN1R to RIGHT_P with 20k input impedance
  cw(0x39, 0x80); // route CM to RIGHT_M with 20k input impedance
  cw(0x3b, 0x0c); // unmute left MICPGA
  cw(0x3c, 0x0c); // unmute right MICPGA

  cw(0x00, 0x00); // select page 0
  cw(0x51, 0xc0); // power up ADC
  cw(0x51, 0x00); // unmute ADC digital volume control

  // DAC
  cw(0x00, 0x00); // select page 0
  //cw(0x01, 0x01); // software reset
  cw(0x0b, 0x82); // NDAC 2
  cw(0x0c, 0x87); // MDAC 7
  cw(0x0d, 0x00); // OSR DAC 128
  cw(0x0e, 0x80); // OSR DAC 128
  cw(0x1b, 0x10); // world length 20bits PTM_P4 (highest performance)
  cw(0x3c, 0x08); // PRB_P8

  cw(0x00, 0x01); // select page 1
  //cw(0x01, 0x08); // disable internal crude avdd
  //cw(0x02, 0x01); // enable AVdd LDO
  cw(0x7b, 0x01); // set REF charging time to 40ms
  //cw(0x14, 0x25); // set HP soft stepping for anti pop
  //cw(0x0a, 0x0B); // set input CM to 0.9V and LO to 1.65V
  cw(0x0e, 0x08); // left DAC reconstruction filter routed to LOL
  cw(0x0f, 0x08); // right DAC reconstruction filter routed to LOR
  cw(0x03, 0x00); // DAC PTM_P3/4
  cw(0x04, 0x00); // DAC PTM_P3/4
  cw(0x12, 0x00); // LOL gain 0dB
  cw(0x13, 0x00); // LOR gain 0dB
  delay(1000);

  cw(0x00, 0x00); // select page 0
  cw(0x3f, 0xd6); // power up and route left digital audio to left dac channel and right to right
  cw(0x40, 0x00); // unmute DAC digital volume


  pinMode(19, OUTPUT); // MCLK enable
  pinMode(20, OUTPUT); // CODEC reset

  i2s.setSysClk(48000);

  i2s.setDOUT(14);
  i2s.setDIN(15);
  i2s.setBCLK(16); // Note: LRCLK = BCLK + 1
  i2s.setMCLK(18);
  i2s.swapClocks();
  i2s.setBitsPerSample(16);
  i2s.setFrequency(48000);
  i2s.setMCLKmult(128); // 6144000Hz 6.144MHz

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

  digitalWrite(19, HIGH); // enable MCLK
  digitalWrite(20, HIGH);
  i2s.begin();

  size_t count, index;
  while (1) {
    count = i2s.read((uint8_t *)&buffer, SIZE * sizeof(int16_t)) * sizeof(uint32_t) / sizeof(int16_t);
    index = 0;
    while (index < count) {
      // Reduce volume by half
      buffer[index++] >>= 1; // right
      buffer[index++] >>= 1; // left
    }
    i2s.write((const uint8_t *)&buffer, count * sizeof(int16_t));
  }
}

void loop() {
  /* Nothing here */
}