void setup() 
{
  pinMode(3, INPUT);
  pinMode(6, OUTPUT);

  esp_deep_sleep_enable_gpio_wakeup(1ULL << 3,ESP_GPIO_WAKEUP_GPIO_HIGH);
  
  Serial.begin(115200);
  Serial.println(F("Going to sleep in 5 seconds."));

  for (int i = 0; i < 10; ++i)
  {
    digitalWrite(6, HIGH);
    delay(250);
    digitalWrite(6, LOW);
    delay(250);
  }

  Serial.println(F("Entering deep sleep."));
  Serial.println(F("Press the button to wake up."));
  
  esp_deep_sleep_start();

  Serial.println(F("This will never be printed."));
}

void loop()
{
  Serial.println(F("This will not be printed."));
  Serial.println(F("The LED will not blink either."));
  
  for (int i = 0; i < 10; ++i)
  {
    digitalWrite(6, HIGH);
    delay(250);
    digitalWrite(6, LOW);
    delay(250);
  }
}