at90can_get_message.c

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// ----------------------------------------------------------------------------
/*
 * Copyright (c) 2007 Fabian Greif, Roboterclub Aachen e.V.
 *  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $Id: at90can_get_message.c 7224 2009-01-25 20:19:32Z fabian $
 */
// ----------------------------------------------------------------------------
 
#include "at90can_private.h"
#ifdef  SUPPORT_FOR_AT90CAN__
 
bool at90can_copy_mob_to_message(can_t *msg)
{
        // read status
        uint8_t cancdmob = CANCDMOB;
        
        // read length
        msg->length = cancdmob & 0x0f;
        
        #if SUPPORT_EXTENDED_CANID
        
        if (cancdmob & (1 << IDE))
        {
                // extended identifier
                uint32_t tmp;
                uint8_t *ptr = (uint8_t *) &tmp;
                
                *ptr       = CANIDT4;
                *(ptr + 1) = CANIDT3;
                *(ptr + 2) = CANIDT2;
                *(ptr + 3) = CANIDT1;
                
                msg->id = tmp >> 3;
                
                /* equivalent to:
                msg->id  = (uint8_t)  CANIDT4 >> 3;
                msg->id |= (uint32_t) CANIDT3 << 5;
                msg->id |= (uint32_t) CANIDT2 << 13;
                msg->id |= (uint32_t) CANIDT1 << 21;
                */
                
                msg->flags.extended = 1;
        }
        else
        {
                // standard identifier
                uint16_t id;
                
                id  = (uint8_t)  CANIDT2 >> 5;
                id |= (uint16_t) CANIDT1 << 3;
                
                msg->id = (uint32_t) id;
                msg->flags.extended = 0;
        }
        
        #else
        
        if (cancdmob & (1 << IDE))
        {
                return false;
        }
        else
        {
                // standard identifier
                msg->id  = (uint8_t)  CANIDT2 >> 5;
                msg->id |= (uint16_t) CANIDT1 << 3;
        }
        
        #endif
        
        if (CANIDT4 & (1 << RTRTAG)) {
                msg->flags.rtr = 1;
        }
        else {
                msg->flags.rtr = 0;
                
                // read data
                uint8_t *p = msg->data;
                for (uint8_t i = 0;i < msg->length;i++) {
                        *p++ = CANMSG;
                }
        }
        
        #if SUPPORT_TIMESTAMPS
        msg->timestamp = CANSTM;
        #endif
        
        return true;
}
 
// ----------------------------------------------------------------------------
 
uint8_t at90can_get_message(can_t *msg)
{
        bool found = false;
        uint8_t mob;
        
        // check if there is any waiting message
        if (!at90can_check_message())
                return 0;
        
        // find the MOb with the received message
        for (mob = 0; mob < 15; mob++)
        {
                CANPAGE = mob << 4;
                
                if (CANSTMOB & (1<<RXOK))
                {
                        found = true;
                        
                        // clear flags
                        CANSTMOB &= 0;
                        break;
                }
        }
        
        if (!found) {
                return 0;               // should never happen
        }
        
        found = at90can_copy_mob_to_message( msg );
        
        #if CAN_RX_BUFFER_SIZE == 0
        // mark message as processed
        ENTER_CRITICAL_SECTION;
        _messages_waiting--;
        LEAVE_CRITICAL_SECTION;
        #endif
        
        // re-enable interrupts
        _enable_mob_interrupt( mob );
        
        // clear flags
        CANCDMOB = (1 << CONMOB1) | (CANCDMOB & (1 << IDE));
        
        if (found) {
                return (mob + 1);
        }
        else {
                // only if SUPPORT_EXTENDED_CANID=0 and a extended message was received
                return 0;
        }
}
 
#endif  // SUPPORT_FOR_AT90CAN__