NI-VISA Serial Bugs Fixed under Labview 7.1?

[Phil_Kas]

I am using legacy serial instrument drivers (originally used with LV 5.1.1) on my application. While troubleshooting this same code for a "silent Labview crash" under Labview 7.0, I was told by NI tech support that it is not a good practice to program a loop in a VI with "NI-VISA OPEN, (read or write), NI-VISA CLOSE" in it. And that the reliable practice was to do a single NI-VISA OPEN at the beginning of the program and an NI-VISA CLOSE at the end. Since these legacy drivers continually open and close NI-VISA (now under the later Labview versions) I would need to rewrite a huge chunk of legacy driver code, unless this problem was fixed under Labview 7.1. Can someone please confirm or not confirm that this NI-VISA Serial Op
en/Close problem was fixed under Labview 7.1?

[JoshuaP]

I believe that this issue was fixed with LabVIEW 7.1 and NI-VISA 3.2. I setup a test on my Windows machine with a loop and just a VISA Open/Close in the loop and let it run for a few minutes. I didn't detect any problems and the Windows Task Manager did not show any memory leaks.

-Josh

[Phil_Kas]

Thanks Josh!

I really need to know the answer to this question with a very high degree of certainty. My production process applications run continuously for weeks if not months and a crash is very very expensive. Just to confirm, are you saying that you are sure NI has fixed this problem and that your limited testing confirms it? Or are you saying that you think that it has been fixed and you did not see it fail in your limited testing?

The reason I am being so particular about your response to my question is that in LV7.0 the symptoms of failures related to the "Looping VISA Open/Close" practice occurred in a somewhat unpredictable manner. Some applications worked fine and others failed only after a random amount of time had passed. Needless to s
ay this was a troubleshooting nightmare.

I just wish to be sure. Can you check with someone at NI and confirm?

Thanks again for your timely comments.

-Phil

[JoshuaP]

Hey Phil,

Actually, there were several known issues of memory leaks with past versions of NI-VISA. As of NI-VISA 3.2 we believe that all of these issues have been fixed. I would suggest upgrading to NI-VISA 3.2, but I am not sure that you need to upgrade to LabVIEW 7.1 to fix the problem.

http://digital.ni.com/softlib.nsf/webcategories/85256410006C055586256BBB002C0E91?opendocument&node=132060_US

We have ran several extensive tests on multiple interfaces and systems and NI-VISA 3.2 seems to have fixed any past issues.

I hope this helps out, and please contact our customer support if you still find any memory leaks or issues with the NI-VISA 3.2 so that our engineering staff can address the problem.

-Josh