md/writeup/avr_echo.md


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title:AVR echo
keywords:avr,echo,c,atmega


# AVR echo
This code tested on ATmega16

```c
#include <avr/io.h>
 
#define FOSC 16000000UL
#define BAUD 9600
#define MYUBRR FOSC/16/BAUD-1
 
void USART_Init( unsigned int ubrr)
{
    UBRRH = (unsigned char)(ubrr>>8);
    UBRRL = (unsigned char)ubrr;
    UCSRB = (1<<RXEN)|(1<<TXEN);
    UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);
}
 
int main()
{
    char c;
    USART_Init( MYUBRR );
    while(1)
    {
        while ( !(UCSRA & (1<<RXC))){};
        c = UDR;
        while (!(UCSRA & (1<<UDRE))){};
        UDR = c;
    }
    return 0;
}
```