int sleepInterval = 5;
unsigned long long uS2S = 1000000;
RTC_DATA_ATTR int bootCount = 0;

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

  Serial.print("Boot number: ");
  Serial.println(bootCount);

  Serial.println("Going to sleep now");

  esp_sleep_enable_timer_wakeup(sleepInterval * uS2S);
  Serial.flush();
  esp_deep_sleep_start();
}

void loop()
{
}