hmm, es funktioniert immer noch nicht... (-.-).

Code:
void Init(void)
{
	//-------- serial interface programmed in boot routine and already running -------
	DDRB |= (1 << PB3);
	//  prepare 36kHz for IR - Communication
	TCCR2 = (1 << WGM20) | (1 << WGM21) | (1 << COM20) | (1 << COM21) | (1 << CS20);
	OCR2  = 0x91; // duty cycle for 36kHz
	TIMSK |= (1 << TOIE2); // 36kHz counter for sleep
	
	// prepare RS232 
	UCSRA = 0x00;
	UCSRB = 0x00;	
	UCSRC = 0x86; // No Parity | 1 Stop Bit | 8 Data Bit
	UBRRL = 0xCF; // 2400bps @ 8.00MHz
	
	// I/O Ports
	DDRB = IRTX | LEFT_DIR | PWM | GREEN_LED; 
	DDRD = RIGHT_DIR | FRONT_LED | ODOMETRY_LED | RED_LED;
	
	// for PWM (8-Bit PWM) on OC1A & OC1B
	TCCR1A = (1 << WGM10) | (1 << COM1A1) | (1 << COM1B1);
	// tmr1 running on MCU clock/8 
	TCCR1B = (1 << CS11);
	
	// A/D Conversion
	ADCSRA = (1 << ADEN) | (1 << ADPS2) | (1 << ADPS1); // clk/64 
	ODOMETRY_LED_OFF;

	FrontLED(OFF);
	BackLED(ON,ON);
	BackLED(OFF,OFF);
	StatusLED(GREEN);
	
	MotorState(FWD,FWD);
	MotorSpeed(0, 0);
	sei();
}
ich habe DDRB |= (1 << PB3); hinzugefügt

was heißt eigentlich "serial interface programmed in boot routine and already running" ???