#include <avr/io.h>
#include <util/delay.h>

void delay_ms(uint16_t t)
{
  while (t--)
    _delay_ms(1);
}

void leds_update(uint8_t index)
{
  uint8_t mask = _BV(PB0) | _BV(PB1) | _BV(PB2) | _BV(PB3) |  _BV(PB4) | _BV(PB5)
               | _BV(PB6) | _BV(PB7);
 
  if (index < 8)
  {
    PORTB = (PORTB & ~mask) | _BV(index);
  }
}

int main (void)
{
  uint8_t selection;
  uint8_t state_sw0, state_sw1;
  uint8_t prev_state_sw0, prev_state_sw1;
 
  /* Setup PB0-7 as outputs */
  DDRB = _BV(PB0) | _BV(PB1) | _BV(PB2) | _BV(PB3) |  _BV(PB4) | _BV(PB5)
       | _BV(PB6) | _BV(PB7);
 
  /* Setup PC0 and PC1 as inputs with pull-up */
  DDRC &= ~(_BV(DDC0) | _BV(DDC1));
  PORTC |= _BV(DDC0) | _BV(DDC1);
   
  /* The first selected led is led 0 */
  selection = 0;
  leds_update(selection);
 
  /* Init the switches state */
  prev_state_sw0 = 0;
  prev_state_sw1 = 0;
 
  /* Main loop */
  for(;;)
  {
    /* Read the current switch state */
    state_sw0 = (PINC & _BV(DDC0));
    state_sw1 = (PINC & _BV(DDC1));
   
    if (state_sw0 && !prev_state_sw0)
    {
      /* The switch 0 has been pressed */
      if (selection < 7)
      {
        selection++;
        leds_update(selection);
      }
    }
   
    if (state_sw1 && !prev_state_sw1)
    {
      /* The switch 1 has been pressed */
      if (selection > 0)
      {
        selection--;
        leds_update(selection);
      }
    }
   
    prev_state_sw0 = state_sw0;
    prev_state_sw1 = state_sw1;
   
    /* Wait for 20ms */
    delay_ms(20);
  }

  return(0);
}