Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Mon, 8 Mar 2004 10:02:09 -0700

On 2004.03.08 09:26, Brian Tieman wrote:
> The biggest problem I have with this Active-X interface and LabView is 
> that CA calls queue up.  There's no support for anything like threads or 
> even events.  The created PV must be in a loop and checked periodically 
> to see if a client requests a change.  Also, once a change has been 
> detected and the LabView process starts doing its thing, any subsequent 
> client requests are ignored until the first request is completed.  The 
> client requests seem to be queued in some manner--which can be a real 
> problem.
> 
> I'm not sure if these issues are inherent to LabView or just my limited 
> experience with LabView development, but I have pulled out significant 
> clumps of hair over these two issues.
As far as I know, it is inherent to LabView.
ActiveX supports "Events" which are asyncronously handled
by e.g. Visual Basic.
But in LabVIEW all you get is a lame "WaitForActiveXEvent.vi".
Just like their idea of VXI interrupts is a "WaitForInterrupt" VI,
indicating that LabVIEW really targets a desk-top lab setup
where you command some GPIB-controlled signal generator,
wait 5 seconds, and then read some GPIB signal analyzer.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System