Atmega 328 sleep

gistfile1.cpp

// source: http://forum.arduino.cc/index.php?PHPSESSID=8lp97jhr4smvi9n29he0ii6eu2&topic=78430.msg2080222#msg2080222


//ATmega328P sleep demo
//
//Wire the usual Arduino LED from PB5 (DIP pin 19, Arduino pin 13) to ground, through
//an appropriate current-limiting resistor.
//Wire a tactile button switch from INT0/PD2 (DIP pin 4, Arduino pin 2) to ground.
//
//The sketch will blink the LED three times, then go to sleep.
//Press the button to generate an interrupt to wake the MCU.
//Best on a breadboard.  Note that voltage regulators and other circuitry on a real Arduino
//will continue to draw current and so the current consumed by just the MCU will be
//difficult to measure.
//While sleeping, I measure < 0.5uA supply current.
//
//Jack Christensen 11Sep2011
//
//Scotchware License: If we meet some day, and you think this is worth it, you can buy me a scotch.

#include <avr/sleep.h>

byte intCounter, adcsra, mcucr1, mcucr2;

void setup(void)
{
    for (byte i=0; i<20; i++) {
        pinMode(i, INPUT);        //make all pins input pins
        digitalWrite(i, HIGH);    //with pullup resistors to minimize power consumption
    }
    pinMode(13, OUTPUT);          //except LED pin
    Serial.begin(115200);
    EICRA = 0x00;                 //configure INT0 to trigger on low level
}

void loop(void)
{
    Serial.print("interrupts: ");
    Serial.println(intCounter, DEC);
    for (byte i=0; i<3; i++) {
        digitalWrite(13, LOW);
        delay(1000);
        digitalWrite(13, HIGH);
        delay(1000);
    }
    digitalWrite(13, LOW);
    sleep_enable();
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    adcsra = ADCSRA;               //save the ADC Control and Status Register A
    ADCSRA = 0;                    //disable ADC
    cli();
    EIMSK |= _BV(INT0);            //enable INT0
    mcucr1 = MCUCR | _BV(BODS) | _BV(BODSE);  //turn off the brown-out detector
    mcucr2 = mcucr1 & ~_BV(BODSE);
    MCUCR = mcucr1;
    MCUCR = mcucr2;
    sei();                         //ensure interrupts enabled so we can wake up again
    sleep_cpu();                   //go to sleep
    sleep_disable();               //wake up here
    ADCSRA = adcsra;               //restore ADCSRA
    digitalWrite(13, LOW);
    pinMode(13, OUTPUT);           //so we can blink the LED some more
}

ISR(INT0_vect)
{
    intCounter++;
    EIMSK &= ~_BV(INT0);           //one interrupt to wake up only
}