at90can.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.c 7538 2009-04-16 13:07:33Z fabian $
 */
// ----------------------------------------------------------------------------

#include "at90can_private.h"
#ifdef  SUPPORT_FOR_AT90CAN__

#include <avr/pgmspace.h>
#include "can_buffer.h"

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

const uint8_t _at90can_cnf[8][3] PROGMEM = {
        // 10 kbps
        {       0x7E,
                0x6E,
                0x7F
        },
        // 20 kbps
        {       0x62,
                0x0C,
                0x37
        },
        // 50 kbps
        {       0x26,
                0x0C,
                0x37
        },
        // 100 kbps
        {       0x12,
                0x0C,
                0x37
        },
        // 125 kbps
        {       0x0E,
                0x0C,
                0x37
        },
        // 250 kbps
        {       0x06,
                0x0C,
                0x37
        },
        // 500 kbps
        {       0x02,
                0x0C,
                0x37
        },
        // 1 Mbps
        {       0x00,
                0x0C,
                0x36
        }
};

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

#if CAN_RX_BUFFER_SIZE > 0
can_buffer_t can_rx_buffer;
can_t can_rx_list[CAN_RX_BUFFER_SIZE];
#else
volatile uint8_t _messages_waiting;
#endif

#if CAN_TX_BUFFER_SIZE > 0
can_buffer_t can_tx_buffer;
can_t can_tx_list[CAN_TX_BUFFER_SIZE];

volatile uint8_t _transmission_in_progress = 0;
#else
volatile uint8_t _free_buffer;                  
#endif

// ----------------------------------------------------------------------------
// get next free MOb

uint8_t _find_free_mob(void)
{
        #if CAN_TX_BUFFER_SIZE == 0
        if (_free_buffer == 0)
                return 0xff;
        #elif CAN_FORCE_TX_ORDER
        if (_transmission_in_progress)
                return 0xff;
        #endif
        
        uint8_t i;
        for (i = 0;i < 15;i++)
        {
                // load MOb page
                CANPAGE = i << 4;
                
                // check if MOb is in use
                if ((CANCDMOB & ((1 << CONMOB1) | (1 << CONMOB0))) == 0)
                        return i;
        }
        
        return 0xff;
}

// ----------------------------------------------------------------------------
// disable interrupt of corresponding MOb

void _disable_mob_interrupt(uint8_t mob)
{
        if (mob < 8)
                CANIE2 &= ~(1 << mob);
        else
                CANIE1 &= ~(1 << (mob - 8));
}

// ----------------------------------------------------------------------------
// enable interrupt of corresponding MOb

void _enable_mob_interrupt(uint8_t mob)
{
        if (mob < 8)
                CANIE2 |= (1 << mob);
        else
                CANIE1 |= (1 << (mob - 8));
}

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

bool at90can_init(uint8_t bitrate)
{
        if (bitrate >= 8)
                return false;
        
        // switch CAN controller to reset mode
        CANGCON |= (1 << SWRES);
        
        // set CAN Bit Timing
        // (see datasheet page 260)
        CANBT1 = pgm_read_byte(&_at90can_cnf[bitrate][0]);
        CANBT2 = pgm_read_byte(&_at90can_cnf[bitrate][1]);
        CANBT3 = pgm_read_byte(&_at90can_cnf[bitrate][2]);
        
        // activate CAN transmit- and receive-interrupt
        CANGIT = 0;
        CANGIE = (1 << ENIT) | (1 << ENRX) | (1 << ENTX);
        
        // set timer prescaler to 199 which results in a timer
        // frequency of 10 kHz (at 16 MHz)
        CANTCON = 199;
        
        // disable all filters
        at90can_disable_filter( 0xff );
        
        #if CAN_RX_BUFFER_SIZE > 0
        can_buffer_init( &can_rx_buffer, CAN_RX_BUFFER_SIZE, can_rx_list );
        #endif
        
        #if CAN_TX_BUFFER_SIZE > 0
        can_buffer_init( &can_tx_buffer, CAN_TX_BUFFER_SIZE, can_tx_list );
        #endif
        
        // activate CAN controller
        CANGCON = (1 << ENASTB);
        
        return true;
}

// ----------------------------------------------------------------------------
// The CANPAGE register have to be restored after usage, otherwise it
// could cause trouble in the application programm.

ISR(CANIT_vect)
{
        uint8_t canpage;
        uint8_t mob;
        
        if ((CANHPMOB & 0xF0) != 0xF0)
        {
                // save MOb page register
                canpage = CANPAGE;
                
                // select MOb page with the highest priority
                CANPAGE = CANHPMOB & 0xF0;
                mob = (CANHPMOB >> 4);
                
                // a interrupt is only generated if a message was transmitted or received
                if (CANSTMOB & (1 << TXOK))
                {
                        // clear MOb
                        CANSTMOB &= 0;
                        CANCDMOB = 0;
                        
                        #if CAN_TX_BUFFER_SIZE > 0
                        can_t *buf = can_buffer_get_dequeue_ptr(&can_tx_buffer);
                        
                        // check if there are any another messages waiting 
                        if (buf != NULL)
                        {
                                at90can_copy_message_to_mob( buf );
                                can_buffer_dequeue(&can_tx_buffer);
                                
                                // enable transmission
                                CANCDMOB |= (1<<CONMOB0);
                        }
                        else {
                                // buffer underflow => no more messages to send
                                _disable_mob_interrupt(mob);
                                _transmission_in_progress = 0;
                        }
                        #else
                        _free_buffer++;
                        
                        // reset interrupt
                        if (mob < 8)
                                CANIE2 &= ~(1 << mob);
                        else
                                CANIE1 &= ~(1 << (mob - 8));
                        #endif
                        
                        CAN_INDICATE_TX_TRAFFIC_FUNCTION;
                }
                else {
                        // a message was received successfully
                        #if CAN_RX_BUFFER_SIZE > 0
                        can_t *buf = can_buffer_get_enqueue_ptr(&can_rx_buffer);
                        
                        if (buf != NULL)
                        {
                                // read message
                                at90can_copy_mob_to_message( buf );
                                
                                // push it to the list
                                can_buffer_enqueue(&can_rx_buffer);
                        }
                        else {
                                // buffer overflow => reject message
                                // FIXME inform the user
                        }
                        
                        // clear flags
                        CANSTMOB &= 0;
                        CANCDMOB = (1 << CONMOB1) | (CANCDMOB & (1 << IDE));
                        #else
                        _messages_waiting++;
                        
                        // reset interrupt
                        if (mob < 8)
                                CANIE2 &= ~(1 << mob);
                        else
                                CANIE1 &= ~(1 << (mob - 8));
                        #endif
                        
                        CAN_INDICATE_RX_TRAFFIC_FUNCTION;
                }
                
                // restore MOb page register
                CANPAGE = canpage;
        }
        else
        {
                // no MOb matches with the interrupt => general interrupt
                CANGIT |= 0;
        }
}

// ----------------------------------------------------------------------------
// Overflow of CAN timer
ISR(OVRIT_vect) {}

#endif  // SUPPORT_FOR_AT90CAN__