Is there any API to check if the CAN Devies are connected or not ?

[vijayendranss]

I use PCAN Driver for Linux v8.

By seeing the manual, i completed till

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sudo modprobe pcan 

When no devices connected to my PC, i execute

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lspcan -T -t -a

No devices are displayed. Till this fine.

In my application i implement like below :

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fd = pcanfd_open(
	st_CanInfoTable[en_channel].dev_name,
	st_CanInfoTable[en_channel].set_flag,
	st_CanInfoTable[en_channel].bitrate
	);
	if (fd > 0){
		pcanfd_set_init(...);
	}
	else{
		printf("pcanfd_open ch=%d ERROR!! errno=%d:%s \n",en_channel, errno, strerror(errno));
	}

When the above is executed, as there are no devices currently connected above ERROR statement will be thrown.
I dont want this to happen.

Library code provided along with software goes like this :

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\peak-linux-driver-8.10.2\lib\src\libpcanfd.c
int pcanfd_open()
{
	.......
	.......
	fd = __open(dev_pcan, o_flags);
	if (fd < 0)
		goto open_exit_1; //return negative fd 
	....
	pcanfd_set_init(...) 
	....
}

I want to modify as below.

• First i would like to "check if the drivers are succesfully loaded" - Is there any API to check this ?

• Then "is there any devices connected or not ?" - Is there any APIs for this ?

If no devices are connected i will not call __open function

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int pcanfd_open()
{
	.......
	.......
	//Check if drivers are loaded ?
	//If loaded{
		// Is there any devices connected or not ? 
		// If (Connected) {
			fd = __open(dev_pcan, o_flags);
			if (fd < 0)
				goto open_exit_1; //return negative fd 
			....
			pcanfd_set_init(...) 
			....
		} //Connected
	} //Loaded
}

[M.Heidemann]

Hello,

There are no specific functions for this in the CAN FD API in the PCAn Linux Driver package, but you can do the following in your code
to get the needed information:

1) Check if the driver is loaded:

You could check if "cat /proc/pcan" returns anything or if /proc/pcan exists, if it does not, the driver is not loaded.

Example:

Driver is not loaded:

DriverNotLoaded.PNG (19.6 KiB) Viewed 4572 times

Driver is loaded:

DriverIsLoaded.PNG (20.95 KiB) Viewed 4572 times

2) Check if the device is connected:

You could check for the device in /dev, it should contain the string "pcan" in its name, if no device with the substring "pcan" can be found, the device is not connected.

PCAN-USB does not show up in /dev if not connected.

Below you can see, once connect it does show up in /dev:

DeviceConnected.PNG (44.63 KiB) Viewed 4572 times

You can check for those two conditions in your code to determine if the device is connected and the driver is loaded.


Best Regards

Marvin

[vijayendranss]

thank you very much for looking into this.

It would be helpful if you can share sample code for this.

[M.Heidemann]

We do not have specific examples for this.

You can take a look at the /test/src directory of the PCAN Linux driver package, it contains the sources for the example applications.

There you can also see how some of these cases are handled, for example if the device cannot be opened:

Here an example from receivetest.c:

OpenDeviceError.PNG (14.92 KiB) Viewed 4567 times

For further questions feel to contact me again.

Best Regards

Marvin

[vijayendranss]

@Marvin
Thanks.. My ultimate purpose is mentioned in the below query.. Can you please have look and guide me.

viewtopic.php?f=119&t=6110

Thanks