Murr

gistfile1.c

// From http://www.instructables.com/id/Vibrating-Timekeeper

#include <avr/sleep.h>
#include <avr/power.h>
#include <avr/wdt.h>
int countr; 

ISR(WDT_vect) {
  countr++;
 }

void setup(){
 pinMode(0, OUTPUT);
  setup_watchdog(6); 
}

void loop() 
{
  ADCSRA &= ~(1<<ADEN); 
  
  sleep_mode();
  
  if (countr>300){
    countr=0;
    digitalWrite(0,HIGH);
    delay(1000);
    digitalWrite(0,LOW);
  }
}

void setup_watchdog(int timerPrescaler) {

  if (timerPrescaler > 9 ) timerPrescaler = 9; //Limit incoming amount to legal settings

  byte bb = timerPrescaler & 7; 
  if (timerPrescaler > 7) bb |= (1<<5); //Set the special 5th bit if necessary

  //This order of commands is important and cannot be combined
  MCUSR &= ~(1<<WDRF); //Clear the watch dog reset
  WDTCR |= (1<<WDCE) | (1<<WDE); //Set WD_change enable, set WD enable
  WDTCR = bb; //Set new watchdog timeout value
  WDTCR |= _BV(WDIE); //Set the interrupt enable, this will keep unit from resetting after each int
}