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Error refreshing com ports

Asked by Stiphu on 5 Mar 2013

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?

3 Comments

Adrian Dronca on 5 Mar 2013

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 on 6 Mar 2013

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 on 30 May 2013

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.

Stiphu

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