Atmega8-16 ADC-ISR

 uint16_t adcval;

 volatile uint16_t ADC_wert;

ISR(ADC_vect)

{ 

 ADC_wert = ADCW;

} 

void ADC_Init(void)

{

  ADMUX = (0<<REFS1) | (1<<REFS0);

  ADCSRA =  (1<<ADEN) | (1<<ADSC) |(1<<ADIE) | (1<<ADPS2) | (1<<ADPS1) |    (1<<ADPS0);     // Frequenzvorteiler auf 128

}

int main(void)

{  

  uart_init( UART_BAUD_SELECT(UART_BAUD_RATE,F_CPU) ); 

  ADC_Init();

  sei();                                   //Globale Interrupts Freigeben

 for (;;)

 {   

  adcval = ADC_wert;

  uint8_t HighBytex = adcval >> 8;

  uint8_t LowBytex  = adcval;

  uart_putc(HighBytex); //High-Byte?

  uart_putc(LowBytex);   //Low-Byte 

 }

}