/*
 * uart.c
 *
 * Code for UART initalization and printf() setup using avr-libc.
 * See uart.h for additional information pertaining to the interface for this module.
 * 
 * Last modified 2010-09-02 22:26
 */
#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdio.h>
#include "uart.h"

/*
 * This function waits for the UART's FIFO transmit buffer to become
 * empty (ready to accept another character), and then stuffs the character
 * to be sent into the output FIFO.
 *
 * In a perfect world, this function would not spin forever waiting for the
 * buffer to be ready, but would give up after the "correct" amount of time
 * and return an error instead.
 */
int put_uart_char(char c, FILE *fd)
{
    while (!(UCSRA & _BV(UDRE)))
        ;	
    UDR = c;            // put character into UART's output buffer

    return 0;
}

/*
 * To initialize the UART for use with avr-libc's printf functions,
 * the UART's line and speed options must be set, then fdevopen() must be used to
 * establish put_uart_char() as the character output routine.  The second parameter
 * to fdevopen() is for providing an input function, and is unsued here.
 */ 
void uart_init(void)
{
    UCSRB |= _BV(TXEN) | _BV(RXEN) | _BV(RXCIE); // enable xmit, recv & recv interrupt
    UCSRC |= _BV(UCSZ1) | _BV(UCSZ0);            // use 8-bit character size
    UBRRH = 0;
    UBRRL = 51;                                  // set 9600 baud with a 8MHz clock

    fdevopen(&put_uart_char, NULL);

    SREG |= _BV(SREG_I);                         // enable global interrupts
}