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/* rs232.c */
/* n.avr.rs232 - AVR RS232 Module. {{{
 *
 * Copyright (C) 2004 Nicolas Schodet
 *
 * 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.
 *
 * Contact :
 *        Web: http://perso.efrei.fr/~schodet/
 *      Email: <contact@ni.fr.eu.org>
 * }}} */
#include "rs232.h"

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

/* Tested AVR check. */
#if defined (__AVR_ATmega8__)
#elif defined (__AVR_ATmega8535__)
#elif defined (__AVR_ATmega128__)
#else
# warning "rs232: not tested on this chip."
#endif

/* UART number. */
#if !defined (UBRRH)
# if defined (UBRR0H)
#  if AC_RS232_PORT == 1
#   define UBRRH UBRR1H
#   define UBRRL UBRR1L
#   define UCSRA UCSR1A
#   define UCSRB UCSR1B
#   define UCSRC UCSR1C
#   define UDR UDR1
#   define SIG_UART_RECV SIG_UART1_RECV
#   define SIG_UART_DATA SIG_UART1_DATA
#  else
#   define UBRRH UBRR0H
#   define UBRRL UBRR0L
#   define UCSRA UCSR0A
#   define UCSRB UCSR0B
#   define UCSRC UCSR0C
#   define UDR UDR0
#   define SIG_UART_RECV SIG_UART0_RECV
#   define SIG_UART_DATA SIG_UART0_DATA
#  endif
#  define PE UPE
# else
#  error "rs232: canot find UBRR."
# endif
#endif

/* UR selector. */
#if defined (URSEL)
# define SELECTOR _BV (URSEL)
#else
# define SELECTOR 0
#endif

/* Unimplemented features. */
#if AC_RS232_CHAR_SIZE != 8
# error "rs232: char size != 8 not implemented."
#endif

/* Baud rate error check. */
#define UBRR_VAL (AC_FREQ / 16 / AC_RS232_BAUDRATE - 1)
#define BAUDRATE (AC_FREQ / 16 / (UBRR_VAL + 1))

#if BAUDRATE - AC_RS232_BAUDRATE > 2
#warning "rs232: baud rate error > 2."
#elif BAUDRATE - AC_RS232_BAUDRATE > 1
#warning "rs232: baud rate error > 1."
#elif BAUDRATE - AC_RS232_BAUDRATE > 0
#warning "rs232: baud rate error > 0."
#endif

/* Mode. */
#define POLLING 0
#define RING 1
#define SEND_MODE AC_RS232_SEND_MODE
#define RECV_MODE AC_RS232_RECV_MODE
#if RECV_MODE == POLLING
# define RECV_IE 0
#else
# define RECV_IE _BV (RXCIE)
#endif

/* Parity. */
#define ODD (_BV (UPM1) | _BV (UPM0))
#define EVEN _BV (UPM1)
#define NONE 0
#define PARITY AC_RS232_PARITY

/* Stop bits. */
#if AC_RS232_STOP_BITS == 1
#define STOP_BITS 0
#elif AC_RS232_STOP_BITS == 2
#define STOP_BITS _BV (USBS)
#else
#error "rs232: bad stop bits value."
#endif

/* Character size. */
#define CHAR_SIZE (_BV (UCSZ1) | _BV (UCSZ0))

/* Buffers. */
#if SEND_MODE == RING
# define SEND_BUFFER_SIZE AC_RS232_SEND_BUFFER_SIZE
# define SEND_BUFFER_MASK (SEND_BUFFER_SIZE - 1)
# if SEND_BUFFER_SIZE & SEND_BUFFER_MASK
#  error "rs232: send buffer size must be a power of 2."
# endif
#endif
#if RECV_MODE == RING
# define RECV_BUFFER_SIZE AC_RS232_RECV_BUFFER_SIZE
# define RECV_BUFFER_MASK (RECV_BUFFER_SIZE - 1)
# if RECV_BUFFER_SIZE & RECV_BUFFER_MASK
#  error "rs232: recv buffer size must be a power of 2."
# endif
#endif

/* Send buffer. */
#if SEND_MODE == RING
uint8_t rs232_send_buffer[SEND_BUFFER_SIZE];
volatile uint8_t rs232_send_head, rs232_send_tail;
#endif

/* Recv buffer. */
#if RECV_MODE == RING
uint8_t rs232_recv_buffer[RECV_BUFFER_SIZE];
volatile uint8_t rs232_recv_head, rs232_recv_tail;
#endif

/* Last error code. */
#define ERROR_BITS (_BV (FE) | _BV (DOR) | _BV (PE))
volatile uint8_t rs232_error_code;

/* +AutoDec */
/* -AutoDec */

/** Initialise rs232. */
void
rs232_init (void)
{
    /* Set baud rate. */
    UBRRH = UBRR_VAL >> 8;
    UBRRL = UBRR_VAL & 0xff;
    UCSRA = 0;
    /* Set format and enable rs232. */
    UCSRC = SELECTOR | PARITY | STOP_BITS | CHAR_SIZE;
    UCSRB = RECV_IE | _BV (RXEN) | _BV (TXEN);
#if RECV_MODE == RING
    rs232_recv_head = 0;
    rs232_recv_tail = 0;
#endif
#if SEND_MODE == RING
    rs232_send_head = 0;
    rs232_send_tail = 0;
#endif
    rs232_error_code = 0;
}

/** Read a char. */
uint8_t
rs232_getc (void)
{
#if RECV_MODE == POLLING
    uint8_t tmperr;
    loop_until_bit_is_set (UCSRA, RXC);
    tmperr = UCSRA & ERROR_BITS;
    if (tmperr)
	rs232_error_code = tmperr;
    return UDR;
#elif RECV_MODE == RING
    uint8_t tmptail = rs232_recv_tail;
    while (rs232_recv_head == tmptail)
	;
    tmptail = (tmptail + 1) & RECV_BUFFER_MASK;
    rs232_recv_tail = tmptail;
    return rs232_recv_buffer[tmptail];
#endif
}

/** Write a char. */
void
rs232_putc (uint8_t c)
{
#if SEND_MODE == POLLING
    loop_until_bit_is_set (UCSRA, UDRE);
    UDR = c;
#elif SEND_MODE == RING
    uint8_t tmphead;
    tmphead = (rs232_send_head + 1) & SEND_BUFFER_MASK;
    while (tmphead == rs232_send_tail)
	;
    rs232_send_buffer[tmphead] = c;
    rs232_send_head = tmphead;
    UCSRB |= _BV (UDRIE);
#endif
}

/** Retrieve error condition, 0 if no error. */
uint8_t
rs232_error (void)
{
    return rs232_error_code;
}

/** Retrieve availlable chars. */
uint8_t
rs232_poll (void)
{
#if RECV_MODE == POLLING
    return UCSRA & _BV (RXC);
#elif RECV_MODE == RING
    return (rs232_recv_head - rs232_recv_tail) & RECV_BUFFER_MASK;
#endif
}

#if RECV_MODE == RING

/* Handle received char for ring buffer. */
INTERRUPT (SIG_UART_RECV)
{
    uint8_t c;
    uint8_t tmphead;
    uint8_t tmperr;
    tmperr = UCSRA & ERROR_BITS;
    if (tmperr)
	rs232_error_code = tmperr;
    c = UDR;
    tmphead = (rs232_recv_head + 1) & RECV_BUFFER_MASK;
    rs232_recv_head = tmphead;
    /* If overflowed, clear the receive buffer. */
    if (tmphead == rs232_recv_tail)
	rs232_error_code = 0xff;
    rs232_recv_buffer[tmphead] = c;
}

#endif /* RECV_MODE == RING */

#if SEND_MODE == RING

/** Handle data register empty for ring buffer. */
INTERRUPT (SIG_UART_DATA)
{
    uint8_t tmptail;
    if (rs232_send_head != rs232_send_tail)
      {
	tmptail = (rs232_send_tail + 1) & SEND_BUFFER_MASK;
	rs232_send_tail = tmptail;
	UDR = rs232_send_buffer[tmptail];
      }
    else
      {
	UCSRB &= ~_BV (UDRIE);
      }
}

#endif /* SEND_MODE == RING */