shift register

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

#define DS_PORT    PORTC
#define DS_PIN     8
#define ST_CP_PORT PORTC
#define ST_CP_PIN  9
#define SH_CP_PORT PORTC
#define SH_CP_PIN  10

#define DS_low()  DS_PORT&=~_BV(DS_PIN)
#define DS_high() DS_PORT|=_BV(DS_PIN)
#define ST_CP_low()  ST_CP_PORT&=~_BV(ST_CP_PIN)
#define ST_CP_high() ST_CP_PORT|=_BV(ST_CP_PIN)
#define SH_CP_low()  SH_CP_PORT&=~_BV(SH_CP_PIN)
#define SH_CP_high() SH_CP_PORT|=_BV(SH_CP_PIN)

//Define functions
//===============================================
void ioinit(void);
void output_led_state(unsigned int __led_state);
//===============================================

int main (void)
{
   ioinit(); //Setup IO pins and defaults

   while(1)
   {
      // Output a knight rider pattern

      for (int i=15;i>=0;i--)
      {
         output_led_state(_BV(i));
         _delay_ms(50);
      }
      for (int i=1;i<15;i++)
      {
         output_led_state(_BV(i));
         _delay_ms(50);
      }
   }
}


void ioinit (void)
{
    DDRC  = 0b00000111; //1 = output, 0 = input
    PORTC = 0b00000000;
}

void output_led_state(unsigned int __led_state)
{
   SH_CP_low();
   ST_CP_low();
   for (int i=0;i<16;i++)
   {
      if ((_BV(i) & __led_state) == _BV(i))  //bit_is_set doesn’t work on unsigned int so we do this instead
         DS_high();
      else
         DS_low();


      SH_CP_high();
      SH_CP_low();
   }
   ST_CP_high();
}