Labview hangs when accessing dll

[lclutchl]

Im accessing an active x dll using labview 8.21.   When we query the dll all parallel loops in labview hang until the dll returns.   Is there a way to get around this behaivour?

[Nadim R]

HI,

I do not know if this will help, but there is an issue with the Call Function Library node in LabVIEW 8.2.1 and is posted in the LabVIEW 8.2.1 Readme help here:

If you configure a Call Library Function Node to call a LabVIEW DLL, place a checkmark in the Specify path on diagram checkbox on the Function page of the Call Library Function dialog box, and select Run in UI thread in the Thread control, LabVIEW hangs when executing the Call Library Function Node. To correct this problem, select Reentrant instead of Run in UI thread in the Thread control. If you configure the Call Library Function Node to call a DLL written in C with these same settings, LabVIEW works correctly.

I hope this helps,

Regards,

Nadim
Applications Engineering
National Instruments

[lclutchl]

Thanks Nadim,    We are using the Active X Automation Open and Invoke Node VIs to talk to the dll.   I take it we would get better performance using the call library function?  

[Nadim R]

Hi,

You are calling the ActiveX dll correctly with Automation open and an invoke node.  It may be the case where calling the dll and executing the dll are extremely resource intensive and causing your LabVIEW program to wait until the dll has finished it's process.   One easy way to verify this is the check your CPU usage when calling the dll.   Have you tested other dlls and do they act the same way?

I hope this helps,

Regards,

Nadim
Applications Engineering
National Instruments

[lclutchl]

Hi Nadim, 

We are using a dual core processor, one of the processors will jump to 80% while the application is loading.   The other processor maintains a constant 23% during that time.   We haven't tested with another activeX dll.  

Thanks,

Ed.