/* Program used for bidirectional motor drive
 * -------------------------------------------
 * Motor is connected between PB0 and PB1 through proper buffers
 * If PD0 is made high, the motor will rotate forward, else it rotates backwards
 */

#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) //(for input) checks if the input is high (Logic 1)

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

	while(1==1) //Infinite loop
	{
		if(is_high(PIND,PD0))
		{
			sbi(PORTB,PB0); //Motor runs forward
			cbi(PORTB,PB1);
		}
		else
		{
			sbi(PORTB,PB1); //Now runs backwards
			cbi(PORTB,PB0);
		}
	}
	return 0;
}