/*
 * uart.c - serial hw routines
 *
 * Written by
 *  Christian Vogelgsang <chris@vogelgsang.org>
 *
 * This file is part of plipbox.
 * See README for copyright notice.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
 *  02111-1307  USA.
 *
 */

#include "global.h"

#include <avr/io.h>
#include <avr/interrupt.h>

#include "uart.h"
#include "timer.h"
#include "board.h"

#ifdef UBRR0H

// for atmeg644
#define UBRRH  UBRR0H
#define UBRRL  UBRR0L
#define UCSRA  UCSR0A
#define UCSRB  UCSR0B
#define UCSRC  UCSR0C
#define UDRE   UDRE0
#define UDR    UDR0

#define RXC    RXC0
#define TXC    TXC0
#define DOR    DOR0
#define PE     UPE0

#endif

// calc ubbr from baud rate
#define UART_UBRR   F_CPU/16/UART_BAUD-1

#define UART_RX_BUF_SIZE 16
#define UART_RX_SET_CTS_POS  2
#define UART_RX_CLR_CTS_POS  13
static volatile u08 uart_rx_buf[UART_RX_BUF_SIZE];
static volatile u08 uart_rx_start = 0;
static volatile u08 uart_rx_end = 0;
static volatile u08 uart_rx_size = 0;

void uart_init(void) 
{
  cli();

  // disable first
  UCSRB = 0;

  // baud rate
  UBRRH = (u08)((UART_UBRR)>>8);
  UBRRL = (u08)((UART_UBRR)&0xff);

  UCSRB = 0x98; // 0x18  enable tranceiver and transmitter, RX interrupt
  UCSRC = 0x86; // 0x86 -> use UCSRC, 8 bit, 1 stop, no parity, asynch. mode

  sei();

  uart_rx_start = 0;
  uart_rx_end = 0;
  uart_rx_size = 0;
}

// receiver interrupt
#ifdef USART_RXC_vect
ISR(USART_RXC_vect)
#else
ISR(USART_RX_vect)
#endif
{
  u08 data = UDR;
  uart_rx_buf[uart_rx_end] = data;

  uart_rx_end++;
  if(uart_rx_end == UART_RX_BUF_SIZE)
    uart_rx_end = 0;
    
  uart_rx_size++;
}

u08 uart_read_data_available(void)
{
  return uart_rx_start != uart_rx_end;
}

u08 uart_read(void)
{
  // wait for buffe to be filled
  while(uart_rx_start==uart_rx_end);

  // read buffer
  cli();

  u08 data = uart_rx_buf[uart_rx_start];
  
  uart_rx_start++;
  if(uart_rx_start == UART_RX_BUF_SIZE)
    uart_rx_start = 0;
  
  uart_rx_size--;  
 
  sei();
  return data;
}

void uart_send(u08 data)
{
  // wait for transmitter to become ready
  while(!( UCSRA & (1<<UDRE)));

  // send byte
  UDR = data;
}