#define BTN_PIN 5

void setup() {
  pinMode(BTN_PIN, INPUT_PULLUP);
  Serial.begin(9600);
  countSetup();
}

void loop() {
  Serial.print("Counter Ticks = ");
  Serial.println(TCNT1);
  delay(250);
}

void countSetup() {
  TCCR1A = 0; // Init Timer1A
  TCCR1B = 0; // Init Timer1B
  TCCR1B |= B00000110; /// Borda de descida (FALLING)
  TCNT1 = 0;
}