mcp2515_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: mcp2515_get_message.c 7224 2009-01-25 20:19:32Z fabian $
 */
// ----------------------------------------------------------------------------

#include "mcp2515_private.h"
#ifdef  SUPPORT_FOR_MCP2515__

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

uint8_t mcp2515_get_message(can_t *msg)
{
        uint8_t addr;
        
        #ifdef  RXnBF_FUNKTION
                if (!IS_SET(MCP2515_RX0BF))
                        addr = SPI_READ_RX;
                else if (!IS_SET(MCP2515_RX1BF))
                        addr = SPI_READ_RX | 0x04;
                else
                        return 0;
        #else
                // read status
                uint8_t status = mcp2515_read_status(SPI_RX_STATUS);
                
                if (_bit_is_set(status,6)) {
                        // message in buffer 0
                        addr = SPI_READ_RX;
                }
                else if (_bit_is_set(status,7)) {
                        // message in buffer 1
                        addr = SPI_READ_RX | 0x04;
                }
                else {
                        // Error: no message available
                        return 0;
                }
        #endif
        
        RESET(MCP2515_CS);
        spi_putc(addr);
        
        // CAN ID auslesen und ueberpruefen
        uint8_t tmp = mcp2515_read_id(&msg->id);
        #if SUPPORT_EXTENDED_CANID
                msg->flags.extended = tmp & 0x01;
        #else
                if (tmp & 0x01) {
                        // Nachrichten mit extended ID verwerfen
                        SET(MCP2515_CS);
                        #ifdef  RXnBF_FUNKTION
                        if (!IS_SET(MCP2515_RX0BF))
                        #else
                        if (_bit_is_set(status, 6))
                        #endif
                                mcp2515_bit_modify(CANINTF, (1<<RX0IF), 0);
                        else
                                mcp2515_bit_modify(CANINTF, (1<<RX1IF), 0);
                        
                        return 0;
                }
        #endif
        
        // read DLC
        uint8_t length = spi_putc(0xff);
        #ifdef RXnBF_FUNKTION
                if (!(tmp & 0x01))
                        msg->flags.rtr = (tmp & 0x02) ? 1 : 0;
                else
                        msg->flags.rtr = (length & (1<<RTR)) ? 1 : 0;
        #else
                msg->flags.rtr = (_bit_is_set(status, 3)) ? 1 : 0;
        #endif
        
        length &= 0x0f;
        msg->length = length;
        // read data
        for (uint8_t i=0;i<length;i++) {
                msg->data[i] = spi_putc(0xff);
        }
        SET(MCP2515_CS);
        
        // clear interrupt flag
        #ifdef RXnBF_FUNKTION
        if (!IS_SET(MCP2515_RX0BF))
        #else
        if (_bit_is_set(status, 6))
        #endif
                mcp2515_bit_modify(CANINTF, (1<<RX0IF), 0);
        else
                mcp2515_bit_modify(CANINTF, (1<<RX1IF), 0);
        
        CAN_INDICATE_RX_TRAFFIC_FUNCTION;
        
        #ifdef RXnBF_FUNKTION
                return 1;
        #else
                return (status & 0x07) + 1;
        #endif
}

#endif  // SUPPORT_FOR_MCP2515__