* This tutorial demonstrates how to open a CAN channel and send a message on it.
#include <stdio.h>
// To use CANlib, we need to include canlib.h and also link to canlib32.lib
// when compiling.
#include "canlib.h"
// The check method takes a canStatus (which is an enumerable) and the method
// name as a string argument. If the status is an error code, it will print it.
// Most Canlib method return a status, and checking it with a method like this
// is a useful practice to avoid code duplication.
void Check(const char* id, canStatus stat)
if (stat != canOK) {
char buf[50];
buf[0] = '\0';
canGetErrorText(stat, buf, sizeof(buf));
printf("%s: failed, stat=%d (%s)\n", id, (int)stat, buf);
void main(int argc, char* argv[]){
// Holds a handle to the CAN channel
canHandle hnd;
// Status returned by the Canlib calls
canStatus stat;
// The CANlib channel number we would like to use
int channel_number = 0;
// The msg will be the body of the message we send on the CAN bus.
char msg[8] = {1, 2, 3, 4, 5, 6, 7, 8};
// The first thing we need to do is to initialize the Canlib library. This
// always needs to be done before doing anything with the library.
printf("Opening channel %d\n", channel_number);
// Next, we open up the channel and receive a handle to it. Depending on what
// devices you have connected to your computer, you might want to change the
// channel number. The canOPEN_ACCEPT_VIRTUAL flag means that it is ok to
// open the selected channel, even if it is on a virtual device.
hnd = canOpenChannel(channel_number, canOPEN_ACCEPT_VIRTUAL);
// If the call to canOpenChannel is successful, it will return an integer
// which is greater than or equal to zero. However, is something goes wrong,
// it will return an error status which is a negative number.
if(hnd < 0){
// To check for errors and print any possible error message, we can use the
// Check method.
Check("canOpenChannel", (canStatus)hnd);
// and then exit the program.
printf("Setting bitrate and going bus on\n");
// Once we have successfully opened a channel, we need to set its bitrate. We
// do this using canSetBusParams. CANlib provides a set of predefined bus parameter
// settings in the form of canBITRATE_XXX constants. For other desired bus speeds
// bus paramters have to be set manually.
// See CANlib documentation for more information on parameter settings.
stat = canSetBusParams(hnd, canBITRATE_250K, 0, 0, 0, 0, 0);
Check("canSetBusParams", stat);
// Next, take the channel on bus using the canBusOn method. This needs to be
// done before we can send a message.
stat = canBusOn(hnd);
Check("canBusOn", stat);
printf("Writing a message to the channel and waiting for it to be sent \n");
// We send the message using canWrite. This method takes five parameters:
// the channel handle, the message identifier, the message body, the message
// length (in bytes) and optional flags.
stat = canWrite(hnd, 123, msg, 8, 0);
Check("canWrite", stat);
// After sending, we wait for at most 100 ms for the message to be sent, using
// canWriteSync.
stat = canWriteSync(hnd, 100);
Check("canWriteSync", stat);
printf("Going off bus and closing channel");
// Once we are done using the channel, we go off bus using the
// canBusOff method. It take the handle as the only argument.
stat = canBusOff(hnd);
Check("canBusOff", stat);
// We also close the channel using the canCloseChannel method, which take the
// handle as the only argument.
stat = canClose(hnd);
Check("canClose", stat);
- The canWriteWait method combines canWrite with canWriteSync. Try it out.
- Use some other program (such as Kvaser CanKing) to listen for messages on
a different channel on the same device as the one used in your
program. Make sure to use the same bitrate.
- Change the fourth parameter in the call to canWrite to 4. What happens to
the message on the receiving side?
- Change the message identifier to something large, like 10000. What happens
on the receiving side? Then, change the fifth parameter to
canMSG_EXT. What happens now?