sja1000_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.
 *
 * $Id$
 */
// ----------------------------------------------------------------------------

#include "sja1000_private.h"
#ifdef  SUPPORT_FOR_SJA1000__

// ----------------------------------------------------------------------------

uint8_t sja1000_get_message(can_t *msg)
{
        uint8_t frame_info;
        uint8_t address;
        
        // check if there is actually a message in the buffers
        if (!sja1000_check_message())
                return FALSE;
        
        frame_info = sja1000_read(16);
        msg->length = frame_info & 0x0f;
        
        if (frame_info & (1<<FF))
        {
                // read extended identifier
                msg->flags.extended = 1;
                
                uint32_t tmp;
                uint8_t *ptr = (uint8_t *) &tmp;
                
                *ptr       = sja1000_read(20);
                *(ptr + 1) = sja1000_read(19);
                *(ptr + 2) = sja1000_read(18);
                *(ptr + 3) = sja1000_read(17);
                
                msg->id = tmp >> 3;
                
                /* equivalent to:
                msg->id  = sja1000_read(20) >> 3;
                msg->id |= (uint16_t) sja1000_read(19) << 5;
                msg->id |= (uint32_t) sja1000_read(18) << 13;
                msg->id |= (uint32_t) sja1000_read(17) << 21;*/
                
                address = 21;
        }
        else
        {
                // read standard identifier
                msg->flags.extended = 0;
                
                uint32_t *ptr32 = &msg->id;             // used to supress a compiler warning
                uint16_t *ptr = (uint16_t *) ptr32;
                
                *(ptr + 1) = 0;
                
                *ptr  = sja1000_read(18) >> 5;
                *ptr |= sja1000_read(17) << 3;
                
                address = 19;
        }
        
        
        if (frame_info & (1<<RTR)) {
                msg->flags.rtr = 1;
        }
        else {
                msg->flags.rtr = 0;
                
                // read data
                for (uint8_t i = 0; i < msg->length; i++) {
                        msg->data[i] = sja1000_read(address + i);
                }
        }
        
        // release buffer
        sja1000_write(CMR, (1<<RRB));
        
        CAN_INDICATE_RX_TRAFFIC_FUNCTION;
        
        return TRUE;
}

#endif  // SUPPORT_FOR_SJA1000__