#define F_CPU 128000UL
#include<avr/io.h>
// regerald, 20171110
struct bits {
  uint8_t b0:1;
  uint8_t b1:1;
  uint8_t b2:1;
  uint8_t b3:1;
  uint8_t b4:1;
  uint8_t b5:1;
  uint8_t b6:1;
  uint8_t b7:1;
} __attribute__((__packed__));
#define SBIT(port,pin) ((*(volatile struct bits*)&port).b##pin)
#define DIO             SBIT( PORTB, 0 )
#define DIO_DDR         SBIT( DDRB,  0 )
#define SCK             SBIT( PORTB, 2 )
#define SCK_DDR         SBIT( DDRB,  2 )
#define RCK             SBIT( PORTB, 1 )
#define RCK_DDR         SBIT( DDRB, 1 )
void spi_wr8( uint8_t val )     // function to write a byte to software SPI
{
  for( uint8_t i = 8; i; i-- ){
    SCK = 0;
    DIO = 0;
    if( val & 0x80 )            // MSB first
      DIO = 1;
    val <<= 1;
    SCK = 1;
  }
}
void displ( int16_t t)         //function to print value on the Led display with two shift registers
{
  if (t<0){t = -1*t;};         //no negative values allowed
  uint8_t numdigit[5];      //splitingt number into digits
    numdigit[0]=t/1000;
    numdigit[1]=t%1000/100;
    numdigit[2]=t%100/10;
    numdigit[3]=t%10;
    numdigit[4]=0;
  const uint8_t chr[5] = {     //digit mask
    0b00001000,  
    0b00000100,  
    0b00000010,  
    0b00000001,
    0b00000000  		//Display of the fifth digit is a walkaround. Otherwise last digit would be brighter than the others. 
  };
  const uint8_t digit[10] = {  // 7 segment mask
    0b11000000, // 0
    0b11111001, // 1
    0b10100100, // 2
    0b10110000, // 3
    0b10011001, // 4
    0b10010010, // 5
    0b10000010, // 6
    0b11111000, // 7
    0b10000000, // 8
    0b10010000 // 9
  };
    
  for(uint8_t i = 0; i <= 4; i++){ 
    RCK = 0;
    spi_wr8(digit[numdigit[i]]);
    spi_wr8(chr[i]);
    RCK = 1;
  }
}
main()
{
  DDRB =0b00000111;  // PB0, PB1, PB2, will now be the output pins for the display
  int16_t t = 0;     //this number is our turn count
  uint8_t ca = 0;    //"case variable", needed to see the direction of turn
  while(1){
    if(bit_is_set(PINB,3) && bit_is_clear(PINB,4) && ca == 0){  //PIN is "clear" when light do not pass
      ca = 1;
    }
    if(bit_is_set(PINB, 3) && bit_is_set(PINB, 4) && ca == 1){
      ca = 2;
    }
    if(bit_is_set(PINB, 4) && bit_is_clear(PINB,3) && ca == 2){
      ca = 3;
    }
    if(bit_is_set(PINB,4) && bit_is_clear(PINB,3) && ca == 0){
      ca = 4;
    }
    if(bit_is_set(PINB, 3) && bit_is_set(PINB, 4) && ca == 4){
      ca = 5;
    }
    if(bit_is_clear(PINB, 4) && bit_is_set(PINB,3) && ca == 5){
      ca = 6;
    }
    if(bit_is_clear(PINB, 3) && bit_is_clear(PINB, 4)){
      ca = 0;
    }
    if (ca == 3){  //turned into ++ direction
      t++;
      ca = 0;      //reset the "case"
    }
    if (ca == 6){  //turned into ++ direction
      t--;
      ca = 0;      //reset the "case"
    }
    displ(t);
  }
}