GPIB::13 13 
Author Message
 GPIB::13 13

What does the following mean GPIB::5 11 in the visa resources?


Tue, 27 Dec 2005 04:01:09 GMT  
 GPIB::13 13
The last number tells which instance.  You can open a VISA Reference
to a GPIB device at address 5 and then open it again without closing
the first one.  You will get GPIB::5 2 the second time.

Wire your VISA reference through each call to make sure you are using
the same reference.  Close all references when you are finished with
them.

Daniel L. Press
PrimeTest Corp.
www.primetest.com



Tue, 27 Dec 2005 04:04:01 GMT  
 GPIB::13 13
I use the same wire from the initialize vi through to the close vi.
Is this what you mean when you say "Wire your VISA reference through
each call to make sure you are using the same reference."  I close my
references with the close.vi


Tue, 27 Dec 2005 04:29:12 GMT  
 GPIB::13 13
If you have one close for each open or initialize, you wouldn't have
multiple instances.


Tue, 27 Dec 2005 04:57:17 GMT  
 GPIB::13 13
Yes, that's what I mean.  There must be someting else in there opening
extra references.  It's hard to say without seeing the code.

 - Dan



Tue, 27 Dec 2005 04:58:04 GMT  
 GPIB::13 13
One thing to try is to use NI Spy.  You will see when your LV code is
causing viOpen to get called.

Another thing to look for is in the initialization in your labview VI.
Check for VISA Open and make sure of 2 things:
1) It is "VISA Open" and not "Old VISA Open".  If so, replace it.
2) The input parameter "Duplicate Session" is set to F not T.  If it
is T, then this will cause new sessions to be created.  If it is F,
then LabVIEW will reuse your existing sessions.

Dan Mondrik
Senior Software Engineer, NI-VISA
National Instruments



Tue, 27 Dec 2005 05:31:24 GMT  
 GPIB::13 13
Thanks.
Is it necessary to use Open and Close visas?


Tue, 27 Dec 2005 20:29:11 GMT  
 GPIB::13 13
Required?  No.  Recommended?  Yes.

It makes the code easier to understand in terms of what you intend.
In other words, "I am just now starting to use this resource here",
and "I am completely finished with this resource here".

For some resources, like Serial, it is more important to close the
resource when you are done with it in LabVIEW, in case you want to use
the resource in a different module or application.  For example, you
might want to do debugging in VISAIC or HyperTerminal.  This is
because only 1 application can use a given Serial resource at a time.
But for other types of resources, the 1-app-only use scenario is not a
restriction.

Dan Mondrik
Senior Software Engineer, NI-VISA
National Instruments



Tue, 27 Dec 2005 22:31:44 GMT  
 
 [ 8 post ] 

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