#include <avr/sleep.h>
#include <avr/wdt.h>

volatile byte data=0;

void setup() {
  pinMode(13,OUTPUT);
  setup_watchdog(9);
// 0=16ms, 1=32ms,2=64ms,3=128ms,4=250ms,5=500ms
// 6=1 sec,7=2 sec, 8=4 sec, 9= 8sec
  ACSR |=_BV(ACD);//OFF ACD
  ADCSRA=0;//OFF ADC
  Sleep_avr();//Sleep_Mode
}

void loop() {

 if(data>=7){
  data=0;
//-------------------------------
   digitalWrite(13,HIGH);
  delay(100);                      //此處是到達(dá)設(shè)置喚醒時(shí)間允許的程序
  digitalWrite(13,LOW); 
//--------------------------------    
Sleep_avr();
 }
 else {
  Sleep_avr();  //Continue Sleep
 }

}

//Sleep mode is activated
void setup_watchdog(int ii) {

  byte bb;

  if (ii > 9 ) ii=9;
  bb=ii & 7;
  if (ii > 7) bb|= (1<<5);
  bb|= (1<<WDCE);

  MCUSR &= ~(1<<WDRF);
  // start timed sequence
  WDTCSR |= (1<<WDCE) | (1<<WDE);
  // set new watchdog timeout value
  WDTCSR = bb;
  WDTCSR |= _BV(WDIE);


}
//WDT interrupt
ISR(WDT_vect) {

  ++data;
 // wdt_reset();

}

void Sleep_avr(){
  set_sleep_mode(SLEEP_MODE_PWR_DOWN  ); // sleep mode is set here
  sleep_enable();
  sleep_mode();                        // System sleeps here
}