Adding sample code for CAN broadcast

README.md

@@ -5,15 +5,26 @@ Example C code for SocketCAN on Linux
 * A simplified tutorial can be found at: https://www.beyondlogic.org/example-c-socketcan-code/
 * Hardcoded to use the vcan0 virtual CAN device.
 
+Make sure the modules are loaded:
+```
+$ modprobe can
+$ modprobe can_raw
+$ modprobe can_bcm # when using broadcast
+```
+
 To install VCAN0:
 ```
 $ ip link add dev vcan0 type vcan
+$ ip link set up vcan0
 ```
+
 Use gcc to build examples:
 ```
 $ gcc cantransmit.c -o cantransmit
 
 $ gcc canreceive.c -o canreceive
 
 $ gcc canfilter.c -o canfilter
+
+$ gcc canbroadcast.c -o canbroadcast
 ```

canbroadcast.c

@@ -0,0 +1,88 @@
+
+#include <stdio.h>
+#include <stdint.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/bcm.h>
+
+#define NUM_FRAMES  1
+
+// Refer to https://github.com/nebaruzdin/can-doc/blob/master/can-bcm.txt for more details
+int main(int argc, char **argv)
+{
+	int s; 
+	struct sockaddr_can addr;
+	struct ifreq ifr;
+
+	printf("CAN Sockets Demo\r\n");
+
+	if ((s = socket(PF_CAN, SOCK_DGRAM, CAN_BCM)) < 0) {
+		perror("Socket");
+		return 1;
+	}
+
+	strcpy(ifr.ifr_name, "vcan0" );
+	ioctl(s, SIOCGIFINDEX, &ifr);
+
+	memset(&addr, 0, sizeof(addr));
+	addr.can_family = AF_CAN;
+	addr.can_ifindex = ifr.ifr_ifindex;
+
+    // Note a CAN_BCM socket must be connected instead of bound after socket
+    //  creation (example without error checking):
+	if (connect(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
+		perror("Connect");
+		return 1;
+	}
+
+    // Create a struct to set up a sequence of four CAN frames
+    struct {
+            struct bcm_msg_head msg_head;
+            struct can_frame frame[NUM_FRAMES];
+    } mytxmsg;
+
+    //   Typically, it is used with a structure in which the components can_id, flags
+    //   (SETTIMER, STARTTIMER), count=0, ival2=100ms, nframes=1 are set and the user
+    //   data in the can_frame structure is filled in accordingly. This variable is then
+    //   transmitted with the write() system call on the socket to BCM.
+    mytxmsg.msg_head.can_id         = 0x690;
+    mytxmsg.msg_head.opcode         = TX_SETUP;
+    mytxmsg.msg_head.flags          = SETTIMER | STARTTIMER | TX_CP_CAN_ID;
+    mytxmsg.msg_head.nframes        = NUM_FRAMES;
+    mytxmsg.msg_head.count          = 0U;
+    mytxmsg.msg_head.ival1.tv_sec   = 0U;
+    mytxmsg.msg_head.ival1.tv_usec  = 0U;
+    mytxmsg.msg_head.ival2.tv_sec   = 1U;    // send every 1 sec
+    mytxmsg.msg_head.ival2.tv_usec  = 0U;
+
+    // When adding TX_CP_CAN_ID in the flags, no need to set can_id here
+    mytxmsg.frame[0].can_dlc        = 8U;
+
+    // Create dummy payload here
+    const uint8_t dummydata[8] = {0xDE, 0xAD, 0xBE, 0xEF, 0xB1, 0x6B, 0x00, 0xB5};
+    memcpy(mytxmsg.frame[0].data, dummydata, 8U);
+
+    if (write(s, &mytxmsg, sizeof(mytxmsg)) != sizeof(mytxmsg)) {
+        perror("Write");
+        return 1;
+    }
+
+    // Wait for a character
+    // During this period that the connection is still established,
+    // the broadcast manager will periodically transmit based on the settings above.
+    char ch = getchar();
+
+	if (close(s) < 0) {
+		perror("Close");
+		return 1;
+	}
+
+	return 0;
+}