Serial VISA problems

[Timo Miettunen]

Hello,

I keep having problems with VISA serial driver. The problem
is that VISA seems to reserve the serial port even after the
VISA session has been closed. Also, if I open COM1 with visa,
I cannot use hyperterminal with COM2. I have to shut donw LabVIEW
in order to use _any_ COM ports after I've used one with VISA.
If i use old serial vi's i don't have to close LV in order to
use COM ports with terminal hyperterminal or procomm
etc.

Has anybody else encountered this kind of behaviour with VISA serial?
I run LabVIEW 5.1f1 in WinNT4.0

timo


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*Timo Miettunen *
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*Senior Test Designer
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[Johannes Niess]

Timo Miettunen writes:

> Hello,
>
> I keep having problems with VISA serial driver. The problem
> is that VISA seems to reserve the serial port even after the
> VISA session has been closed. Also, if I open COM1 with visa,
> I cannot use hyperterminal with COM2. I have to shut donw LabVIEW
> in order to use _any_ COM ports after I've used one with VISA.
> If i use old serial vi's i don't have to close LV in order to
> use COM ports with terminal hyperterminal or procomm
> etc.
>
> Has anybody else encountered this kind of behaviour with VISA serial?
> I run LabVIEW 5.1f1 in WinNT4.0

Timo,

An easy workaround might be using the "close all visa sessions" option
in the preferences/Misc tab. Before this option was introduced I used
the
visa sessions.vi in .../Labview/vi.lib/visa.llb .

Do you use "find visa resources" and maybe you do some homemade "plug
and play" by retrieving info strings from all ports? I'd look for
sessions not getting closed in your programm.

I'm using LV 5.1f0 on NT4.0SP3 and didn't see your kind of problem. I
doubt it is an NT permissions problem.

Johannes Niess

[Taucher]

Hi Timo,

I have the same trouble in LabView 6.1
There is a very awful workaround: After using the Visa-functions in my Vi (including the close-visa-vi), I open and close the serial port with the old Vi's.
After doing that, the port is 'realy' closed ....

Marco