Error refreshing com ports

My computer is connected to a LED light source over a virtual com port. The LED light source crashes from time to time. If this is the case, I have to restart it, which I can do over this com port (the crash is a power failure. The light source is not working properly anymore, but I still can communicate with it). The problem is, that after the restart, I'm not anymore able to connect to it. I'm trying to establish a new connection with

    connection = serial('COM14','BaudRate',9600);
    fopen(connection)

If I execute the fopen command, I get the following error message:

    Error using serial/fopen (line 72)
    Open failed: Port: COM14 is not available. Available ports: COM12,
    COM14, COM15.
    Use INSTRFIND to determine if other instrument objects are connected to    
    the requested device.

If I restart Matlab, I am able to reconnect. Do you know if there is any workaround?

[Adrian Dronca]

If you are able to reconnect after restart my guess is that Matlab opens the connection and keeps it open, or keeps it in the memory.

Then you cannot connect anymore because it is already in use.

Do you also close it ?

Edit: one hint is that you have an error in your code. Do you always check for errors ?

[Stiphu]

Yes, I do close the com port. And there is no error in the code, or do you see one in this two lines of code? The strange thing is that it says that Port 14 is not available and then says that Port 14 is available.

[Benjamin]

I'm experiencing the same problem and would be very interested in a solution (port unavailable, yet available). The port is closed and deleted, yet I get the following message:

fopen(serial('COM3'))

Open failed: Port: COM3 is not available. Available ports:
COM3, COM5, COM6, COM7, COM8.

It can be solved by restarting the system. Until it fails again after some hours of com port use.

[Bergercookie]

I had the same problem. There is a similar post ( http://www.mathworks.com/matlabcentral/newsreader/view_thread/145681 ) in which a working solution is presented.

Essentially you can resolve the problem by issuing the following command

delete(instrfindall);

[Siddharth Rajesh]

delete(instrfindall);

This statement has solved my issue, thank you so much for you help.

[abhinay kumar]

This also solved my problem. Thank You.

[a m]

This also solved my problem. Thank You.

[ehsan ghaderi]

This also solved my problem. very very Thank You .

[Amirabbas Amrollahi]

where sould i add this suggested comand?

[Mahmoud Abulwafa]

at the end i guess

[Walter Roberson]

It would go at the beginning. It would clean up after whatever had gone before.

You should also make sure to release the port when you are done with it.

[Ashirwad Gad]

@Walter Roberson, thanks for that tip on releasing the port. Now how is it done exactly or is it the same as delete(instrfindall) ?

[Walter Roberson]

delete() the serial port object when you are through with it. Consider using an onCleanup() in case of a code crash

[Ashirwad Gad]

alright thanks!

Answer 1

[Nhat Nguyen Thanh Minh]

thanks for your help !