Initialise

  //Enable gobal interrupts (should already be enabled but do anyway)
  SREG = SREG | B10000000;

Turning interrupt on

  //Enable analog comparator interrupt
  ACSR = B00000010;        //On failing edge (bit 1=1), AIN0 applied to positive input of the analog comparator (bit6=0)

  ACSR = ACSR | B00001000;        // Enable analog comparator interrupt (bit 3).

Turning interrupt off

  ACSR = 0;

Interrupt function

ISR(ANALOG_COMP_vect)
{


}