/* port_test3.c
 * Turns one of the pins PB0,PB1,PB2,PB3 high depending on the inputs PD0 and PD1
 * Can be used for controlling two motors bidirectionally only one motor runs at a time.
 */

#include <avr/io.h> //standard include for ATMega16
#define sbi(x,y) x |= _BV(y) //set bit
#define cbi(x,y) x &= ~(_BV(y)) //clear bit
#define tbi(x,y) x ^= _BV(y) //toggle bit
#define is_high(x,y) ((x & _BV(y)) == _BV(y))

int main(void)
{
    DDRB=0xff; //PORTB as OUTPUT
    PORTB=0x00;
    DDRD=0x00;//PORTD as INPUT
    PORTD=0xff;

    while(1==1) //Infinite loop
    {
        if(is_high(PIND,PD0) && is_high(PIND,PD1))
        {
            cbi(PORTB,PB0); //First motor stopped
            cbi(PORTB,PB1);
            cbi(PORTB,PB2); //Second motor running forward
            sbi(PORTB,PB3);

        }
        else if(is_high(PIND,PD0) && !is_high(PIND,PD1))
        {
            cbi(PORTB,PB0); //First motor running forward
            sbi(PORTB,PB1);
            cbi(PORTB,PB2); //Second motor stopped
            cbi(PORTB,PB3);
        }
        else if(!is_high(PIND,PD0) && is_high(PIND,PD1))
        {
            cbi(PORTB,PB0); //First motor stopped
            cbi(PORTB,PB1);
            sbi(PORTB,PB2); //Second motor running backwards
            cbi(PORTB,PB3);
        }
        else if(!is_high(PIND,PD0) && !is_high(PIND,PD1))
        {
            sbi(PORTB,PB0); //First motor running backwards
            cbi(PORTB,PB1);
            cbi(PORTB,PB2); //Second motor stopped
            cbi(PORTB,PB3);
        }
    }
    return 0;
}