uart.c

#include <avr/io.h>
#include <stdio.h>
#define BAUD 115200
#include <util/setbaud.h>

void uart_init(void) {
	UBRR0H = UBRRH_VALUE;
	UBRR0L = UBRRL_VALUE;

#if USE_2X
	UCSR0A |= _BV(U2X0);
#else
	UCSR0A &= ~(_BV(U2X0));
#endif

	UCSR0C = _BV(UCSZ01) | _BV(UCSZ00); /* 8-bit data */
	UCSR0B = _BV(RXEN0) | _BV(TXEN0);   /* Enable RX and TX */
}

int uart_putchar(char c, FILE *stream) {
	if (c == '\n') {
		uart_putchar('\r', stream);
	}
	loop_until_bit_is_set(UCSR0A, UDRE0);
	UDR0 = c;
	return 0;
}