canjam2.c

/* simple copy of can examples to filter on a specific ID and turn the light bits on
 *  this filters on the smart Car id 423:3FF  and or's on the bits in the second byte:
 *      xx x3	where 01 is right, 02 is left
 *  which turn on the indicator lights for turn signal / emergency flasher on the dashboard instrument cluster
 *  doing this in compiled C as python3 is a bit slow for the fast can bus
 *  when the message id 423 is received, or the second byte with 0x03 and immediately re-send it - overwriting
 *  the original message
 *  this version has two length 50 for loops in the infinite loop to switch back and forth between the two lights
 *  that gives them about a second on each
 * 
 *   original source:    https://github.com/craigpeacock/CAN-Examples
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/socket.h>

#include <linux/can.h>
#include <linux/can/raw.h>

int main(int argc, char **argv)
{
        int s, i;
        int nbytes;
        struct sockaddr_can addr;
        struct ifreq ifr;
        struct can_frame rframe;
        struct can_frame tframe;

        printf("CAN control Demo\r\n");

        if ((s = socket(PF_CAN, SOCK_RAW, CAN_RAW)) < 0) {
                perror("Socket");
                return 1;
        }

        strcpy(ifr.ifr_name, "can0" );
        ioctl(s, SIOCGIFINDEX, &ifr);

        memset(&addr, 0, sizeof(addr));
        addr.can_family = AF_CAN;
        addr.can_ifindex = ifr.ifr_ifindex;

        if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
                perror("Bind");
                return 1;
        }

        struct can_filter rfilter[1];

        rfilter[0].can_id   = 0x423;
        rfilter[0].can_mask = 0x7FF;
        tframe.can_id = 0x423;
        tframe.can_dlc = 8;


        setsockopt(s, SOL_CAN_RAW, CAN_RAW_FILTER, &rfilter, sizeof(rfilter));

	while(1) {
		for(int k=0; k<50; k++) {
			nbytes = read(s, &rframe, sizeof(struct can_frame));

		        if (nbytes < 0) {
		                perror("Read");
       			        return 1;
       	 		}
			for (i = 0; i < rframe.can_dlc; i++)
				tframe.data[i] = rframe.data[i];
			tframe.data[1] |= 0x01;
	       		if (write(s, &tframe, sizeof(struct can_frame)) != sizeof(struct can_frame)) {
              		  	perror("Write");
                		return 1;
			}
		}
                for(int k=0; k<50; k++) {
                        nbytes = read(s, &rframe, sizeof(struct can_frame));

                        if (nbytes < 0) {
                                perror("Read");
                                return 1;
                        }
                        for (i = 0; i < rframe.can_dlc; i++)
                                tframe.data[i] = rframe.data[i];
                        tframe.data[1] |= 0x02;
                        if (write(s, &tframe, sizeof(struct can_frame)) != sizeof(struct can_frame)) {
                                perror("Write");
                                return 1;
                        }
                }

	}
}