#include <TimerOne.h>
#define PIN_LED 8
#define PIN_BUTTON 11
int FLAG_LED=0;

void setup() 
{
  Timer1.initialize(1000);
  Timer1.attachInterrupt(Systick_Handler);
  pinMode(PIN_LED, OUTPUT);
  pinMode();

}

void Systick_Handler(void)
{
  static int divisor = 1000;

  divisor--;
  if(divisor == 0)   //entro cada 1 segundo
  {
    divisor = 1000;
    
    
  }
}

void loop() 
{
  
  if(FLAG_LED==0)           
  {
    digitalWrite(PIN_LED, LOW);
    FLAG_LED=1;
    delay(2000);
  }
  else
  {
    digitalWrite(PIN_LED, HIGH);
    FLAG_LED=0;
    delay(2000);
  }

}