#include <avr/io.h>
#include <avr/interrupt.h>


#define DIV1024	5
#define DIV256	4
#define DIV64 	3
#define DIV8 	2
#define FULL 	!(PINB & (1<<PIN1)) && !(PINB & (1<<PIN2))	//on 	on
#define HALF 	!(PINB & (1<<PIN1)) && (PINB & (1<<PIN2))	//off	on
#define QUARTER (PINB & (1<<PIN1)) && !(PINB & (1<<PIN2))	//on	off
#define EIGHT 	(PINB & (1<<PIN1)) && (PINB & (1<<PIN2))	//off	off

//MS1 pin 7 PORTB2
//MS2 pin 6 PORTB1

volatile int fullMode;

void step (void)
{
	if (fullMode > 0)
	{
		if (fullMode == 2) 
		{
			PORTB ^= (1<<PIN0);
			fullMode=1;
		}
		else fullMode=2;
	}

	else
	PORTB ^= (1<<PIN0);
}


ISR(TIMER0_COMPA_vect) //Timer/Counter0 Overflow interrupt routine
{

	step();
}

int main (void)
{
	uint8_t previous = 1; 
	uint8_t current = (PINB & 36);
	//Port configuration
	DDRB |= (1<<PIN0); //PORTBB, PIN0 output
	PORTB |= (1<<PIN0);
	PORTB |= (1<<PIN7) | (1<<PIN6);
	
	//Timer initialization
	TCCR0A |= (1<<WGM01);
	TCCR0B = DIV64;	//Timer/Counter0 prescaler
	TIMSK |= (1<<OCIE0A);	//Timer/Counter0 Overflow Interrupt Enable
	OCR0A = 76;
	/* OCR0A values
	300ms period (ordinary step) =76/div64
	150ms period (half step) 37/div64
	75ms period (quarter step) 18/div64
	37.5ms period (eight step) 76/div8
	*/
	sei(); //Enable interrupts globally

	while(1)
	{
		current = (PINB & 6);

		if (current != previous)
		{
			if 		(FULL) 		{ OCR0A=143;	TCCR0B=DIV1024;	fullMode=1;	}
			else if (HALF) 		{ OCR0A=143;	TCCR0B=DIV1024; fullMode=0;	}
			else if (QUARTER) 	{ OCR0A=71; 	TCCR0B=DIV1024;	fullMode=0;	}
			else if (EIGHT) 	{ OCR0A=71; 	TCCR0B=DIV256;  fullMode=0;	}
			
			previous = current;
		}
	}

	return 0;
}