#include <avr/sleep.h>

#define BUTTON_PIN 2
#define LED_PIN 13

volatile bool wakeup = false;

void wakeUp()
{
  wakeup = true;
}

void setup()
{
  Serial.begin(96000);

  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);

  digitalWrite(LED_PIN, HIGH);

  Serial.println("ACTIVE MODE");

  delay(5000);

  Serial.println("ENTERING SLEEP MODE");

  digitalWrite(LED_PIN, LOW);

  attachInterrupt(digitalPinToInterrupt(BUTTON_PIN),
                  wakeUp,
                  FALLING);

  set_sleep_mode(SLEEP_MODE_PWR_DOWN);

  sleep_enable();

  sleep_mode();
  sleep_disable();

  Serial.println("WOKE UP");

  digitalWrite(LED_PIN, HIGH);
}

void loop()
{
}