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标题: AT90CAN128的CAN收发程序 [打印本页]

作者: 因为思念谁 时间: 2016-6-14 18:51
标题: AT90CAN128的CAN收发程序
最近研究这块芯片，也找了点资料，现在整理完的程序如下，和大家分享。

can.h
******************************************************************************/

#ifndef __can_h__
#define __can_h__

struct MOb
{
      unsigned long id;
      unsigned char data [8];
};

void can_init (void);
void can_tx (struct MOb msg);
void can_rx (struct MOb msg);

#endif

****************************************************************************************************************

#include <avr/io.h>
#include "can.h"

/****************************************************************/
/* CAN initialization                                              */
/****************************************************************/
void can_init (void)
{
      //reset CAN interface
      CANGCON |= (1<<SWRES);

      //reset all MObs
      for (unsigned char i=0; i<15; i++)
      {
            CANPAGE = (i<<4);       //select MOb
            CANCDMOB = 0;             //disable MOb
            CANSTMOB = 0;             //clear status
            CANIDT1 = 0;             //clear ID
            CANIDT2 = 0;
            CANIDT3 = 0;
            CANIDT4 = 0;
            CANIDM1 = 0;             //clear mask
            CANIDM2 = 0;
            CANIDM3 = 0;
            CANIDM4 = 0;
            for (unsigned char j=0; j<8; j++)
                     CANMSG = 0;       //clear data
      }

      // set CAN -> baudrate
      // bit timing -> datasheet 264 (check table)
      // 250Kbps 16MHz cpu-clk
      CANBT1 = 0x0E;for
      CANBT2 = 0x04;
      CANBT3 = 0x13;

      // clear CAN interrupt registers
      CANGIE = 0;                      // none interrupts
      CANIE1 = 0;                      // none interrupts on MObs
      CANIE2 = 0;
      CANSIT1 = 0;
      CANSIT2 = 0;

      //start CAN interface
      CANGCON = (1<<ENASTB);

      //wait until module ready
      while (!(CANGSTA & (1<<ENFG)));
}

/****************************************************************/
/* CAN transmission via mailbox 1 (polling)                      */
/****************************************************************/
void can_tx (struct MOb msg)
{
      //enable MOb1, auto increment index, start with index = 0
      CANPAGE = (1<<4);

      //set IDE bit, length = 8
      CANCDMOB = (1<<IDE) | (8<<DLC0);

      //write 29 Bit identifier
      msg.id <<= 3;
      CANIDT4 = (unsigned char) (msg.id&0xF8);
      CANIDT3 = (unsigned char) (msg.id>>8);
      CANIDT2 = (unsigned char) (msg.id>>16);
      CANIDT1 = (unsigned char) (msg.id>>24);

      //put data in mailbox
      for (unsigned char i=0; i<8; i++)
            CANMSG = msg.data ;

      //enable transmission
      CANCDMOB |= (1<<CONMOB0);

      //wait until complete
      while (!(CANSTMOB & (1<<TXOK)));

      //reset flag
      CANSTMOB &= ~(1<<TXOK);
}

/****************************************************************/
/* CAN reception evia mailbox 0 (polling)                      */
/****************************************************************/
void can_rx (struct MOb msg)
{

      CANHPMOB=0;

      //select MOb0
      CANPAGE = 0x00;       //select MOb0

      //clear MOb flags
      CANSTMOB = 0;

      // select ID which can be receive
      CANIDT4 = (uint8_t) (msg.id << 3);
      CANIDT3 = (uint8_t) (msg.id >> 5);
      CANIDT2 = (uint8_t) (msg.id >> 13);
      CANIDT1 = (uint8_t) (msg.id >> 21);

      // set mask in order to receive only the message with the ID
      CANIDM4 = 248;
      CANIDM3 = 255;
      CANIDM2 = 255;
      CANIDM1 = 255;
      // enable extended ID
      CANIDM4 |= (1<<IDEMSK);

      // enable reception and
      CANCDMOB=(1<<CONMOB1) | (1<<IDE);

      // wait until reception is complete
      while(!(CANSTMOB&(1<<RXOK)));

      // reset flag
      CANSTMOB &= ~(1<<RXOK);

      // get data
      for (unsigned char i=0; i<(CANCDMOB&0xf); i++)
            msg.data = CANMSG;

      //get identifier which has to be the same like ID
      msg.id = 0;
      msg.id |= ((unsigned long) CANIDT1<<24);
      msg.id |= ((unsigned long) CANIDT2<<16);
      msg.id |= ((unsigned long) CANIDT3<<8);
      msg.id |= (CANIDT4&0xF8);
      msg.id >>= 3;
}

**************************************************************************************************************************

#include <avr/io.h>
#include <stdlib.h>
#include "usart0.h"
#include "can.h"

// message to receive
struct MOb msg={0x1,{0,0,0,0,0,0,0,0}};

// toggle the LED on the Crumb-Board
#define toggleLED() (DDRB^=(1<<7))

int main(){
      // init usart on 19200 8N1 at 16 MHz cpu clock
      usart0_init(51);
      // greet the world
      usart0_transmit_string("Hello World\n");
      // init the can interface
      can_init();

      while(1){
            // send can message
            can_rx(msg);

            toggleLED();
      }
}
***************************************************************************************
usart0.c

#include <avr/io.h>
#include "usart0.h"

/* Initialize UART */
void usart0_init( unsigned int baudrate )
{
      /* Set the baud rate */
      UBRR0H = (unsigned char) (baudrate>>8);
      UBRR0L = (unsigned char) baudrate;

      /* Enable UART receiver and transmitter */
      UCSR0B = ( ( 1 << RXEN0 ) | ( 1 << TXEN0 ) );

      /* Set frame format: 8N1 */
      UCSR0C = (1<<UCSZ01)|(1<<UCSZ00);
}

/* Read and write functions */
unsigned char usart0_receive( void )
{
      /* Wait for incomming data */
      while ( !(UCSR0A & (1<<RXC0)) );
      /* Return the data */
      return UDR0;
}

void usart0_transmit( unsigned char data )
{
      /* Wait for empty transmit buffer */
      while ( !(UCSR0A & (1<<UDRE0)) );
      /* Start transmittion */
      UDR0 = data;
}

void usart0_transmit_string(char* p){
      while (*p)
            usart0_transmit(*p++);
}

*******************************************************************************************************************
usart0.h

#ifndef __usart0_h__
#define __usart0_h__

void usart0_init( unsigned int baudrate );
unsigned char usart0_receive( void );
void usart0_transmit( unsigned char data );
void usart0_transmit_string(char* p);

#endif

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