LabVIEW PDA and WinCE

[PPLLC]

Greetings all,

My latest stab at the bleeding edge of LabVIEW capabilities has brought me to yet another question for which I haven't found an answer... Does the PDA module take advantage of the fact that Win CE is a deterministic OS or are thread prioritization and interrupt servicing isolated by the RTE from the OS? My hunch is that LV PDA doesn't make use of the deterministic capabilities of CE, but I really hope I'm wrong.

Chris

[JLS]

Hello,

I inquired with R&D about this and the answer I obtained was that there is no special isolation of processes from the OS by LabVIEW PDA.  As far as development is concerned, the block diagram can still of course allow a programmer to define "parallel" processes, but all that really matters is how the code is compiled, and the official word was that PDA doesn't do anything special and that "thread prioritization and interrupt servicing" are NOT "isolated by the RTE from the OS."

I hope this helps!

Best Regards,

JLS

[PPLLC]

Thanks for the input, JLC.

I probably should be a little clearer... I was concerned that the thread prioritization in PDA on CE worked like it does when running standard LV on XP (for example). It is my understanding that the prioritizing is only applicable within the RTE. Additionally, I don't believe there is any way under XP to set the interrupt for a DAQ card to a higher priority than the mouse, for example, without extensively reconfiguring the system after disabling ACPI.

Upon further contemplation, however, it would seem that if WinCE is guaranteed to service an interrupt within 5ms, the pressure is on me to write code in the PDA module that can deal with the data within the required system response time minus the 5ms used to acknowledge the interrupt. 

Please let me know if I am not interpreting something correctly.

[JLS]

Hello,

My suspicion is that LabVIEW threads run at normal priority, in line with the "nothing special."  I have inquired a bit deeper about this, however, and I'll post anything relevant I hear back to this thread.

Great questions - sorry I don't know off the top of my head 🙂

Best Regards,

JLS

[JLS]

Hello,

Ok, here's the final word:

1. All LabVIEW PDA applications are single threaded.

2. The system default thread priority is used - which on WinCE is likely THREAD_PRIORITY_NORMAL (which is level 3 on a scale from 0 to 7)

See the following microsoft document for more information: (see the "Threads and Thread Priority" section specifically)

http://www.microsoft.com/technet/prodtechnol/wce/plan/realtime.mspx

I hope that helps clarify things for you!

Best Regards,

JLS

[PPLLC]

Thank you for all of your effort, JLS. After reading the article and thinking about what R&D has said regarding the PDA module, I think there may be a way to make things work. Since CE is multithreaded, I could write 2 apps, one for acquisition and one for analysis, in order to keep acquisition and data processing speed high. If I investigate CE a bit more, I'll bet there is a way to programatically set thread priority from within LabVIEW - either with a C widget or a direct call to a CE library. If I figure that out, then the possibilities for using the PDA module get very interesting.

[Bob_Y.]

I'm interested in what you figure out.  Let me know if there is anything that I can do to help out.   I can run test code or even help with research if you need it.  My e-mail is boby@distek.com if you need to send me a request.

Thanks,
Bob Young

[JLS]

Hello,

No problem!  I hope you find that you're able to use PDA the way you'd like to, and if you can post the results of your exploration, I am sure others will benefit from it!

Thanks for the update, and best of luck!

JLS

[Vincent_Carpentier]

Did anyone got any success in building 2 LabVIEW PDA application to implement a multithread application?

Thanks,

Vincent