volatile bool LED0_STATE = false;
volatile bool LED1_STATE = false;

void setup() {
  Serial.begin(9600);
  pinMode(13, OUTPUT);        //Set the pin to be OUTPUT
  pinMode(7, OUTPUT);        //Set the pin to be OUTPUT
  
  // TIMER 0 should not be used - it is already used by millis and delay

  // TIMER 1 in Normal (overflow) mode for interrupt every 4 sec-ish
  noInterrupts(); // disable interrupts while we setup 
  // reset Timer 1 configurations, default to interrupt on overflow
  TCCR1A = 0; 
  TCCR1B = 0;
  // set bits 0-2 to select the scalar value
  // 001 = 1,  010 = 8, 011 = 64, 100 = 256, 101 = 1024
  TCCR1B = (TCCR1B & 0b11111000) | 0b101;   // Pre-scalar = 1024
  // enable timer 1 overflow interrupt by setting bit 0 of TIMSK1
  TIMSK1 |= 1; 
  interrupts();  // enable all interrupts

  noInterrupts(); // stop interrupts - same as cli()
  // TIMER 2 in CTC mode with interrupts at 125Hz
  TCCR2A = 0; TCCR2B = 0; // set entire registers to 0
  TCNT2  = 0; //initialize counter value to 0
  OCR2A = 124; // = (16*10^6) / (125*1024) - 1 (must be < 256)
  TCCR2A |= (1 << WGM21); // turn on CTC mode
  TCCR2B |= (1 << CS02) | (1 << CS01) | (1 << CS00); // 1024 prescaler
  TIMSK2 |= (1 << OCIE2A); // enable timer compare interrupt
  interrupts(); // enable interrupts - same as sei()
}

void loop() {
  // put your main code here, to run repeatedly:

}

ISR(TIMER1_OVF_vect) {
  LED1_STATE = !LED1_STATE;      //Invert LED state
  digitalWrite(13, LED1_STATE);  //Write new state to the LED on pin D5  
}

ISR(TIMER2_COMPA_vect){
  LED0_STATE = !LED0_STATE;
  digitalWrite(7, LED0_STATE);
  //Serial.println(millis());
}