#ifndef F_CPU
#warning "F_CPU was not defined yet, now make up with 4000000"
#define F_CPU 4000000L                    // Systemtakt in Hz - define as  long>> Without errors in the computation 
#endif


#define BAUD 9600L
#define UBRR_VAL ((F_CPU+BAUD * 8)/(BAUD*16)-1)     //clever round
#define BAUD_REAL (F_CPU/(16*(UBRR_VAL+1)))         //real baud rate
#define BAUD_ERROR ((BAUD_REAL*1000)/BAUD-1000)     //Error per thousand


#if ((BAUD_ERROR>10)||(BAUD_ERROR<-10))
#error Systematic error in the baud rate more than 1% and thus too high!
#endif


#include <avr/io.h>
#include <stdlib.h>
#include <inttypes.h>
#include <util/delay.h>


//for USART0
void USART_Init(void) 
{
  
  UBRR0H = (unsigned char)(UBRR_VAL>>8);            // Set baud rate
  UBRR0L = (unsigned char)UBRR_VAL;
  
  UCSR0B |= (1<<RXEN)|(1<<TXEN);                    // Enable receiver and transmitter
  
  UCSR0C =  (1<<UCSZ00)|(1<<UCSZ01);    // Set frame format: 8data, 1stop bit        

}//end USART_Init()

void USART_Putc(unsigned char c)
{
    while (!(UCSR0A & (1<<UDRE0))); // Do nothing until data have been transmited 
    
    UDR0 = c;                      // Put data into Buffer, sends the data
    _delay_ms(10);   
}//end USART_Putc()

//function which send a String Through uart
void USART_Puts (char *string)
{
    while( *string != '\0' )    //as long as *string != '\0' so unlike the "stringer end-character"
    {  
        USART_Putc(*string);
        string++;
    }
}//end USART_Puts()


unsigned char UART_Getc()
{    
    while( !(UCSR0A & (1<<RXC)) );    // Do nothing until data have been recieved and is ready to be read from UDR 
    
    return UDR0;                        //Get and receive data from Buffer
}//end USART_Receive()


int main(void) 
{
    DDRC = 0xFF;                        // define as output 
    USART_Init();
    USART_Puts("\r\n");
    USART_Puts("Messung gestartet:");            // receives data
    
   unsigned char received;
  
  while(1) 
  {
        received = UART_Getc();                   // sends data
         PORTC = 0xEF
      if(received == 0x0D)                   // = ENTER-Taste
             USART_Puts("\r\n");
     else 
    {
    USART_Puts("\r\n");
        USART_Putc(received );
        if(   (received >= 0x61 && received <= 0x7A)     //a      bis      z
           || (received >= 0x41 && received <= 0x5A)       //A     bis     Z 
           || (received >= 0x30 && received <= 0x39)      //0      bis     9 
           || (received == 0x20)                       ) //<SPACE>
       
        USART_Puts("\r\n");
    USART_Putc(received);
    USART_Puts("\r\n");
     }
  }
   return 0;                     
} //end main()