How do I close an open instrument handle following an error?

I'm using MATLAB 2018a on Windows 10 Enterprise.

I'm writing code to talk to and read from instruments that are on a LAN interface.

I use commands similar to:

instrOfInterest_handle = visa('agilent', sprintf('TCPIP0::%s::inst0::INSTR, IpAddressStruct.instrOfInterest)

to find the instrument handle, and then commands similar to:

fopen(instrOfInterest_handle);

to open communication with the instrument.

I normally close the communication with a command similar to

fclose(instrOfInterest_handle);

However, since I'm writing / developing the code, sometimes I make mistakes and the program I'm developing halts in an error state, before running the command to close the communcations.

When that happens, I'm unable to re-open the communication channel to the instrument. Instead, I get an error similar to:

Warning: : Unsuccessful open: The specified configuration:
TCPIP0::IpAddressOfInterest::inst0::INSTR is not available
Use INSTRHWINFO for a list of available configurations.  Use INSTRFIND to determine if other instrument objects are connected to the requested instrument.

If I was getting an error similar to this when trying to write to a file, I'd run the

fclose('all');

command. However, there doesn't appear to be anything similar when writing to instruments.

The only way I've figured out to be able to re-open the communications channel to the instrument is to kill off MATLAB and then restart it.

I figure there has to be a better way; I just don't know what that better way is.

Answer 1

[Rik]

You may be interested in oncleanup. When a variable goes out of scope, that function can run code.

Alternatively you can put all code between open and close in a separate function. Then you can easily put that in a try catch block.