//Turn off ADC (analog to digital conversion)
//
//Next thing we can do turn off the ADC subsystem by adding this line:
//  // disable ADC
//  ADCSRA = 0;  
//
//With that there the power consumption drops a large amount, down from 
//335 µA to 0.355 µA! (that is, 355 nA)


#include <avr/sleep.h>

void setup () 
{

  for (byte i = 0; i <= A5; i++)
    {
    pinMode (i, OUTPUT);    // changed as per below
    digitalWrite (i, LOW);  //     ditto
    }
    
  // disable ADC
  ADCSRA = 0;  
  
  set_sleep_mode (SLEEP_MODE_PWR_DOWN);  
  noInterrupts ();           // timed sequence follows
  sleep_enable();
 
  // turn off brown-out enable in software
  MCUCR = bit (BODS) | bit (BODSE);
  MCUCR = bit (BODS); 
  interrupts ();             // guarantees next instruction executed
  sleep_cpu ();              // sleep within 3 clock cycles of above

}  // end of setup

void loop () { }