#include <ESP_I2S.h>
#define SCK 5
#define WS 25
#define SDOUT 35

const int buff_size = 128;
// int available, read;
// uint8_t buffer[buff_size];
I2SClass I2S;

void setup() {
  I2S.setPins(bclk = SCK, ws = WS, dout = SDOUT, din=-1, mclk=-1)
  //I2S.setPins(5, 25, 26, 35, 0); //SCK, WS, SDOUT, SDIN, MCLK
  I2S.begin(I2S_MODE_STD, 16000, I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_STEREO);

  
  //I2S.end();
}

void loop() {
  uint8_t wave = -1;
  I2S.write(wave, 1);
  wave = - wave; 
}