SRF05 macht Probleme

#define F_CPU 16000000UL 

#include <avr/interrupt.h>

#include <util/delay.h>

#include <avr/io.h>

#define START_CLK  0x0A        // Start clock with 1:8 prescaler CTC mode

#define START_CLK_N  0x02        // Start clock running 1:8 prescaler in normal mode

#define STOP_CLK  0x08        // Stop clock

void init_Ultraschall(void)

{

  DDRA |= (1<<PA7);      // Port A Pin 7 als Ausgang. Rest als Eingang

  TCCR1A = 0x00;      // TIMER 1 in CTC mode

  TCCR1B = 0x08;  

  startTimer_init_Ultraschall(0xFFF);

}

void startTimer_init_Ultraschall (unsigned int time)

{

  OCR1A = time;      // Time set to count to

  TIFR = 0x10;      // Clear timer campare match flag

  TCNT1 = 0x00;       // Clear timer to zero

  TCCR1B = START_CLK;    // Start timer running 1:8 prescaler

}

void waitForTimer(void)

{

  while(!(TIFR&0x10));  // wait for timer to set compare match flag

  TCCR1B = STOP_CLK;    // Stop the timer

}

unsigned int getEcho(void) 

{

unsigned int range;

  while(!(PINA&(1<<PA6)));    // Wait for echo pin to go high,  this indicates the start of the incoming pulse

  TCNT1 = 0x00;         // Clear timer to zero

  TCCR1B = START_CLK_N;    // Start timer running 1:8 prescaler in normal mode

  while((PINA&(1<<PA6)));      // Wait for echo pin to go low signaling that the pulse has ended

  TCCR1B = STOP_CLK;      // Stop the timer and set back to CTC mode  

  range = TCNT1/58;      // Read back value in the timer counter register, this number divided by 58 will give us the range in CM

  return(range);

}

void startRange(void)

{

  PORTA = ( 1<<PA7 );    // Trigger Pin auf High

  _delay_us(30);

  PORTA &= ~(1<<PA7 );  // Trigger Pin auf LOW

}