Sampling rate and ticks period

Kernel
5

I tried this code, but doesn’t work. For some reason i can’t decrease period time between samples to less than 0,667 [ms], even when i change the middle parameter in timerAlarmWrite. In this case i putted in 0,5 [ms]. What it could happen? Im thinking that it can be limited by the time of the execution in analogRead function, but i hope not.

#include <Arduino.h>
#include "esp_timer.h"

volatile int interruptCounter;

int totalInterruptCounter;

hw_timer_t * timer = NULL;

portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;

void IRAM_ATTR onTimer() {

  portENTER_CRITICAL_ISR(&timerMux);

  interruptCounter++;

  portEXIT_CRITICAL_ISR(&timerMux);

}

void setup() {

  Serial.begin(115200);

  timer = timerBegin(0, 80, true);

  timerAttachInterrupt(timer, &onTimer, true);

  timerAlarmWrite(timer, 500, true);

  timerAlarmEnable(timer);

}

void loop() {

  if (interruptCounter > 0) {

    portENTER_CRITICAL(&timerMux);

    interruptCounter--;

    Serial.println((analogRead(12)-1937)*0.681);    

    portEXIT_CRITICAL(&timerMux);

  }

}