Probier das:
Code:
#include <avr/io.h>         // I/O Port definitions
#include <avr/interrupt.h>   // Interrupt macros

#define F_CPU 16000000

#define timer 235                     //0.01ms

volatile int ms1 = 0;
volatile int ms2 = 0;
volatile int ms3 = 0;

void timer_init(void){
   TCNT0 = timer;
   TIMSK |= (1<<TOIE0);                           //Interupts aktivieren 
   sei();
   TCCR0 |= (1<<CS01);      //Prescaler 8
}

ISR(TIMER0_OVF_vect){
   TCNT0 = timer;   
   //Endausschlag LINKS
	if(ms1>=150){
		PORTB &= ~(1<<PORTB1);
		if(ms1<=2000)
			ms1++;
		else
			ms1 = 0;
	}
	else
      PORTB |= (1<<PORTB1);
/*      
   if(ms2>=150)
      PORTB &= ~(1<<PORTB2);
   else
      PORTB |= (1<<PORTB2);
   if(ms2<=2000)
      ms2++;
   else
      ms2 = 0;

      
   if(ms3>=150)
      PORTB &= ~(1<<PORTB3);
   else
      PORTB |= (1<<PORTB3);
   if(ms3<=2000)
      ms3++;
   else
      ms3 = 0;
*/
}

int main(void){
   DDRB |= (1<<PORTB1) | (1<<PORTB2) | (1<<PORTB3);         //B... AUSGANG
   PORTB &= ~((1<<PORTB1) | (1<<PORTB2) | (1<<PORTB3));      //B.. Low

                                       //GLOBALE INTERUPTS AKTIVIERT
	timer_init();
	while(1){
   
  	}
   	return 0;
}