Hi Frédéric,

On line 16 of this patch you are defining BAUD_SYNC to 0 in the header file. Then later on, you check to see if it is not defined, if so then define BAUD_SYNC to 0. Shouldn't that first definition on line 16 be removed?

I noticed that util/setbaud.h cannot calculate baudrate for sync mode.

I did the following modification to the file. I doubt it will it the
next release, but I do beleive it is a good thing to have.

Basic explanation:
if BAUD_SYNC is define and equal to 1, a modified macro is use to
calculate baud rate.
If BAUD_SYNC is define and equal to 0 or not define, macro works as before.

Modification should not break code that use the current version of setbaud.h.

Usage could be:
#include <avr/io.h>

#define F_CPU 4000000

static void uart_9600(void)
{
#define BAUD_SYNC 1
#define BAUD 9600
Device specific declaration
#define XCK_DDR DDRB//For ATmega16A
#define XCK_DDx DDB0
#include <util/setbaud.h>
   UBRRH = UBRRH_VALUE;
   UBRRL = UBRRL_VALUE;
   UCSRC = _BV(1<<UMSEL);
   Configure as clock source
   XCK_DDR |= _BV(1<<XCK_DDx);
}