watchdog.h

// Creds go to: combs, https://github.com/combs/Arduino-Watchdog-Handler
//
// Helper for setting up watchdog interrupt function.
//
// Define your interrupt routine in ISR(WDT_vect) { }
//
// Any variables used in your interrupt routine should be declared
// volatile to avoid sadness

#ifndef WATCHDOG_H
#define WATCHDOG_H

#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif

void setup_watchdog(int timerPrescaler) {

  if (timerPrescaler > 9 ) timerPrescaler = 9; // Correct incoming amount if need be

  byte bb = timerPrescaler & 7;

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


#if defined __AVR_ATmega328P__ || defined __AVR_ATmega168P__ || defined __AVR_ATmega168__ || defined __AVR_ATmega328__ || defined __AVR_ATmega328V__ || defined __AVR_ATmega168V__

  // ATmega328p or ATmega168p -- Arduino Uno, etc.

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


#elif defined __AVR_ATtiny85__ || defined __AVR_ATtiny45__ ||   defined __AVR_ATtiny25__

    // ATtiny85, 45, 25

  // 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

#else
  //??
#error "I don't know how to handle your AVR in setup_watchdog"
#endif

}



#endif