//Power Reduction Register (PRR)
//
//
//The next thing to experiment with is the Power Reduction Register 
//(PRR). This lets you "turn off" various things inside the processor.
//
//
//The various bits in this register turn off internal devices, 
//as follows:
//
//
//    Bit 7 - PRTWI: Power Reduction TWI
//    Bit 6 - PRTIM2: Power Reduction Timer/Counter2
//    Bit 5 - PRTIM0: Power Reduction Timer/Counter0
//    Bit 4 - Res: Reserved bit
//    Bit 3 - PRTIM1: Power Reduction Timer/Counter1
//    Bit 2 - PRSPI: Power Reduction Serial Peripheral Interface
//    Bit 1 - PRUSART0: Power Reduction USART0
//    Bit 0 - PRADC: Power Reduction ADC
    
#include <avr/sleep.h>
#include <avr/power.h>

void setup () 
{

  // disable ADC
  ADCSRA = 0;  

  // turn off various modules
  power_all_disable ();
  
  set_sleep_mode (SLEEP_MODE_IDLE);  
  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 () { }