/*
 * This is an example to read analog data at high frequency using the I2S peripheral
 * Run a wire between pins 27 & 32
 * The readings from the device will be 12bit (0-4096)
 */
#include <driver/i2s.h>

#define I2S_SAMPLE_RATE 78125
#define ADC_INPUT ADC1_CHANNEL_4 //pin 32
#define OUTPUT_PIN 27
#define OUTPUT_VALUE 3800
#define READ_DELAY 10000 //microseconds

void i2sInit()
{
   i2s_config_t i2s_config = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX | I2S_MODE_ADC_BUILT_IN),
    .sample_rate =  I2S_SAMPLE_RATE,              // The format of the signal using ADC_BUILT_IN
    .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT, // is fixed at 12bit, stereo, MSB
    .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
    .communication_format = I2S_COMM_FORMAT_I2S_MSB,
    .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
    .dma_buf_count = 4,
    .dma_buf_len = 8,
    .use_apll = false,
    .tx_desc_auto_clear = false,
    .fixed_mclk = 0
   };
   i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
   i2s_set_adc_mode(ADC_UNIT_1, ADC_INPUT);
   i2s_adc_enable(I2S_NUM_0);
}

void reader(void *pvParameters) {
  uint32_t read_counter = 0;
  uint64_t read_sum = 0;
  while(1){
    size_t bytes_read = 0;
    uint16_t buffer = 0;
    i2s_read(I2S_NUM_0, &buffer, sizeof(buffer), &bytes_read, portMAX_DELAY);
    buffer = ~buffer;            // The data is inverted
    //Serial.println(buffer % 0x1000);
    read_sum += buffer % 0x1000; // The 4 high bits are the channel
    read_counter++;
    if (bytes_read != sizeof(buffer)) Serial.println("buffer empty!");
    if (read_counter == I2S_SAMPLE_RATE) {
      Serial.printf("avg: %d\n", read_sum/I2S_SAMPLE_RATE);
      read_counter = 0;
      read_sum = 0;
      i2s_adc_disable(I2S_NUM_0);
      delay(READ_DELAY);
      i2s_adc_enable(I2S_NUM_0);

    }
  }
}

void setup() {
  Serial.begin(115200);
  // Put a signal out on pin 
  uint32_t freq = ledcSetup(0, I2S_SAMPLE_RATE, 10);
  Serial.printf("Output frequency: %d\n", freq);
  ledcWrite(0, OUTPUT_VALUE/4);
  ledcAttachPin(OUTPUT_PIN, 0);
  // Initialize the I2S peripheral
  i2sInit();
  // Create a task that will read the data
  xTaskCreatePinnedToCore(reader, "ADC_reader", 2048, NULL, 1, NULL, 1);
}

void loop() {}