Atmega8 Uart Interrup

#include <avr/io.h>

#include <stdlib.h>

#include <avr/interrupt.h>

#define F_CPU 4000000

#include <util/delay.h>

#define BAUD 9600

#define UBRR_VAL F_CPU/16/BAUD-1

volatile uint16_t wert;

#define UART_MAXSTRLEN 10

volatile uint8_t uart_str_complete = 0;     // 1 .. String komplett empfangen

volatile uint8_t uart_str_count = 0;

volatile char uart_string[UART_MAXSTRLEN + 1] = "";

char buffer[10];            // oder ein anderer passender Wert

void delay_ms(int delay) 

{

  int i;

  for (i=0;i<=delay;i++) 

  {

    _delay_ms(1);

  }

}

void init_uart(unsigned int ubrr)

{

  UBRRH = (unsigned char)(ubrr>>8);

  UBRRL = (unsigned char)(ubrr);

  UCSRB |= (1<<RXEN);

  UCSRB |= (1<<TXEN);

  UCSRB |= (1<<RXCIE);

  UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);

}

void send_char(unsigned char data) 

{

        while (!(UCSRA & (1<<UDRE)));

        UDR = data;

}

void send_string(char *data) 

{

  while (*data)

  {

      send_char(*data);

      data++;

  }

}

ISR(USART_RXC_vect)

{

  unsigned char nextChar;

  // Daten aus dem Puffer lesen

  nextChar = UDR;

  if( uart_str_complete == 0 ) {  // wenn uart_string gerade in Verwendung, neues Zeichen verwerfen

    // Daten werden erst in string geschrieben, wenn nicht String-Ende/max Zeichenlänge erreicht ist/string gerade verarbeitet wird

    if( nextChar != '\n' &&

        nextChar != '\r' &&

        uart_str_count < UART_MAXSTRLEN - 1 ) {

      uart_string[uart_str_count] = nextChar;

      uart_str_count++;

    }

    else {

      uart_string[uart_str_count] = '\0';

      uart_str_count = 0;

      uart_str_complete = 1;

    }

  }

}

int main(void) {

  init_uart(UBRR_VAL);

    while(1)

  {

   _delay_ms(1000);  

        wert = uart_string; 

  send_string("wert: ");

  send_string(utoa(wert, buffer, 10));

  }

}