int main(void)
{
  DDRB = 0xFF; // outport for monitoring result
  DDRD = 0b00000111; // port connected to spi slave devices
  
  PORTD |= 0b00000011;
  
  uint32_t result=0; // buffer for result
  uint8_t i; // counter variable

  Delay(100000);
  
  PORTD &= ~_BV(0); // pull pin 0 low (enable slave #1)

  Delay(100);
  
  while(1)
  {
    result = 0; // clear result buffer
		
	for (i=0; i<19; i++)
	{
      PORTD |= _BV(2); // pull clock high
	  
	  Delay(100);

      result |= ((PIND & _BV(3))!=0)<<18; // read data bit
	  result >>= 1; // and shift right
	
	  Delay(100);

	  PORTD &= ~_BV(2); // pull clock low

	  Delay(100);
    }

	PORTB = result>>12;

	PORTD |= _BV(0); // slave disable

	Delay(100);
  
    PORTD &= ~_BV(0); // slave enable

	Delay(100);
  }

  return 0;
}