#include <ioCAN128v.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);
 
void can_init (void)
{
unsigned char i,j;
//reset CAN interface
CANGCON |= (1<<SWRES);
//reset all MObs
for ( 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 ( j=0; j<8; j++)
CANMSG = 0; //clear data
}
// set CAN -> baudrate
// bit timing -> datasheet 264 (check table)
// 250Kbps 16MHz cpu-clk
CANBT1 = 0x0E;//16M/8=2M
CANBT2 = 0x04;//3QT
CANBT3 = 0x13;//2+2=4
// 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<<1);
//wait until module ready
while (!(CANGSTA & (1<<ENFG)));
}
 

void can_tx (struct MOb msg)
{
unsigned char i;
//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 (i=0; i<8; i++)
CANMSG = msg.data [i];
//enable transmission
CANCDMOB |= (1<<CONMOB0);
//wait until complete
while (!(CANSTMOB & (1<<TXOK)));
//reset flag
CANSTMOB &= ~(1<<TXOK);
}
 
 
void can_rx (struct MOb msg)
{
unsigned char i;
CANHPMOB=0;
//select MOb0
CANPAGE = 0x00; //select MOb0
//clear MOb flags
CANSTMOB = 0;
// select ID which can be receive
CANIDT4 = (unsigned char)(msg.id << 3);
CANIDT3 = (unsigned char)(msg.id >> 5);
CANIDT2 = (unsigned char)(msg.id >> 13);
CANIDT1 = (unsigned char)(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 (i=0; i<(CANCDMOB&0xf); i++)
msg.data [i] = 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;
}