#include <driver/adc.h>
#include <driver/timer.h>

hw_timer_t *timer = NULL;

const int bufferSize = 4096;
uint16_t rawData[bufferSize]; // Buffer for ADC capture

volatile int sampleCnt = 0;
volatile int timerstop = 0;

void IRAM_ATTR onTimer() {

  if (sampleCnt < 4096) {
    rawData[sampleCnt++] = adc1_get_raw(ADC1_CHANNEL_0) >> 4; // Reduce 12-bit to 8-bit
  } else {
    timerstop = 1;
  }
}


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

  // ADC Setup
  adc1_config_width(ADC_WIDTH_BIT_12);
  adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_DB_11); // GPIO36 (VP)

  // 32000 Hz
  timer = timerBegin(40000000);
  timerAttachInterrupt(timer, &onTimer);
  timerAlarm(timer, 1250, true, 0);
}
void loop() {

  static unsigned long elapse = micros();

  if (timerstop) {
    elapse = micros() - elapse;
    timerStop(timer);
    float freq = 1000000.0 * (sampleCnt + 1) /  elapse;
    Serial.println(freq, 2);
    Serial.println(rawData[10]);
    sampleCnt = 0;
    timerstop = 0;
    timerStart(timer);
    elapse = micros();
  }
}