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/* twi.c */
/* n.avr.twi - AVR TWI Module. {{{
 *
 * Copyright (C) 2004 Cl�ment Demonchy
 *
 * Robot APB Team/Efrei 2005.
 *        Web: http://assos.efrei.fr/robot/
 *      Email: robot AT efrei DOT fr
 *
 * 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 "twi_slave.h"
#include "n/avr/rs232/rs232.h"

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

static volatile uint8_t twi_rcpt_tail;
static volatile uint8_t send_idx;
static volatile uint8_t data_ready;
static volatile uint8_t buf_rcpt[SIZE_BUF_RCPT];
static volatile uint8_t buf_send1[SIZE_BUF_SEND];
static volatile uint8_t buf_send2[SIZE_BUF_SEND];
static volatile uint8_t *buf_send_sys, *buf_send_user;
static volatile int8_t send_switch;
static volatile int8_t state;

void
twi_init (uint8_t addr)
{
    state = 0;
    send_switch = 0;
    buf_send_sys = buf_send1;
    buf_send_user = buf_send2;
    TWAR = addr;
    TWSR = 0x00;
    TWCR = _BV(TWEA) | _BV(TWEN) | _BV(TWIE);
}


SIGNAL (SIG_2WIRE_SERIAL)
{
    rs232_putc (';');
    switch (TW_STATUS)
      {
      /* slave transmitter mode */
      /* START + SLA|W + ACK */
      case TW_ST_SLA_ACK:
      case TW_ST_ARB_LOST_SLA_ACK:
	state = 1;
	rs232_putc ('a');
	send_idx = 0;
	/* no break */
      case TW_ST_DATA_ACK:
	rs232_putc ('b');
	TWDR = buf_send_sys[send_idx++];
	if (SIZE_BUF_SEND == send_idx)
	    TWCR &= ~_BV(TWEA);
	break;
      case TW_ST_DATA_NACK:
      case TW_ST_LAST_DATA:
	rs232_putc ('c');
	TWCR |= _BV (TWEA);
	break;
      /* slave receiver mode */
      /* START + SLA|W + ACK */
      case TW_SR_SLA_ACK:
      case TW_SR_ARB_LOST_SLA_ACK:
      case TW_SR_GCALL_ACK:
      case TW_SR_ARB_LOST_GCALL_ACK:
	rs232_putc ('z');
	state = 2;
	data_ready = 0;
	twi_rcpt_tail = 0;
	if (SIZE_BUF_RCPT == 1)
	    TWCR &= ~_BV(TWEA);
	break;
      /* DATA + ACK */
      case TW_SR_DATA_ACK:
      case TW_SR_GCALL_DATA_ACK:
	rs232_putc ('y');
	buf_rcpt[twi_rcpt_tail++] = TWDR;
	if (SIZE_BUF_RCPT - twi_rcpt_tail == 1)
	    TWCR &= ~_BV(TWEA);
	break;
      /* DATA + NACK */
      case TW_SR_DATA_NACK:
      case TW_SR_GCALL_DATA_NACK:
	rs232_putc ('x');
	buf_rcpt[twi_rcpt_tail++] =  TWDR;
	/* no break */
      /* STOP */
      case TW_SR_STOP:
	rs232_putc ('w');
	data_ready = 1;
	if (state && send_switch) /* send */
	  {
	    volatile uint8_t *tmp;
	    /* Thibault paye son coup */
	    tmp = buf_send_user;
	    buf_send_user = buf_send_sys;
	    buf_send_sys = tmp;
	    send_switch = 0;
	    state = 0;
	  }
	break;
      }
    TWCR |= _BV(TWINT);
}

/** Recopie dans les donn�es recues dans buf.
 */
uint8_t
twi_poll (uint8_t buf[], uint8_t size)
{
    if (data_ready)
      {
	data_ready = 0;
	while (size --)
	    buf[size] = buf_rcpt[size];
	TWCR |= _BV (TWEA);
	return 1;
      }
    else
	return 0; 
}

void
twi_update (uint8_t buf[], uint8_t size)
{
    volatile uint8_t *tmp;
    while (size --)
	buf_send_user[size] = buf[size];
    /* si pas occup� on swap les pointeurs */
    if (!state)
      {
	tmp = buf_send_user;
	buf_send_user = buf_send_sys;
	buf_send_sys = tmp;
      }
    else
	send_switch = 1;
}