#include <avr/io.h>
#define BAUD_PRESCALE 103 
 
void USART_Transmit( char data ) 
{
while ((UCSR0A & (1 << UDRE0)) == 0) {}; //Ожидание опустошения буфера приема
UDR0 = data; //Начало передачи данных	
} 
 
int main (void) 
{ 
    char ReceivedByte; 
 
    UCSR0B |= (1 << RXEN0) | (1 << TXEN0);   // Turn on the transmission and reception circuitry 
    UCSR0C |= (1 << UCSZ00) | (1 << UCSZ01); // Use 8-bit character sizes 
 
    UBRR0L = BAUD_PRESCALE; // Load lower 8-bits of the baud rate value into the low byte of the UBRR register 
    UBRR0H = (BAUD_PRESCALE >> 8); // Load upper 8-bits of the baud rate value into the high byte of the UBRR register 
 
	USART_Transmit('O');//Передаем при включении
	USART_Transmit('k');//сообщение "Ok!", что свидетельствует
	USART_Transmit('!');//о правильно работе программы 
	USART_Transmit(0x0d);//переход в начало строки
	USART_Transmit(0x0a);//переход на новую строку 
 
    for (;;) // Loop forever 
    { 
       while ((UCSR0A & (1 << RXC0)) == 0) {}; // Do nothing until data have been recieved and is ready to be read from UDR 
       ReceivedByte = UDR0; // Fetch the recieved byte value into the variable "ByteReceived" 
 
       while ((UCSR0A & (1 << UDRE0)) == 0) {}; // Do nothing until UDR is ready for more data to be written to it 
       UDR0 = ReceivedByte; // Echo back the received byte back to the computer 
    }    
 }