/* Make avr-libc's printf etc. write to the serial port.
   (Originally written for the Arduino Transterpreter.)
   Adam Sampson <ats@offog.org> */

#include <avr/io.h>
#include <stdint.h>
#include <stdio.h>

#ifdef __AVR_ATmega8__
#define TXEN0 TXEN
#define UBRR0H UBRRH
#define UBRR0L UBRRL
#define UCSR0A UCSRA
#define UCSR0B UCSRB
#define UDR0 UDR
#define UDRE0 UDRE
#endif

static int serial_write(char c, FILE *f) {
	/* Wait for transmit buffer to be empty */
	while ((UCSR0A & _BV(UDRE0)) == 0)
		;

	/* Put byte into transmit buffer */
	UDR0 = c;

	return 0;
}

void serial_stdout_init(long speed) {
	/* Set baud rate */
	uint16_t factor = (F_CPU / 16 + speed / 2) / speed - 1;
	UBRR0H = factor >> 8;
	UBRR0L = factor;

	/* Set format (8N1). */
#ifdef __AVR_ATmega8__
	/* The ATmega8 differs from the 328 in that you have to set URSEL to
	   get the right register here, since UCSRC and UBRRH are actually the
	   same register... */
	UCSRC = _BV(URSEL) | (3 << UCSZ0);
#else
	UCSR0C = 3 << UCSZ00;
#endif

	/* Enable transmitter */
	UCSR0B = _BV(TXEN0);

	/* Set up stdout to write to the serial port */
	stdout = fdevopen(serial_write, NULL);
}