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pda Wireless

I am developping an wireless PDA application on IPAQ 2490 with Labview 8.0 and i have this behavior
 
- I have a primary loop wich read and receive continiously the TCP-IP data from computer and show it. on PDA Question here, If i dont receive continiously, i lost the wireless communication after few second. This behavior doesn't not appear un standard TCP connection, It is normal ???
 
- I have a second loop in parralel with queuing message. When this loop call a VI with "Open on call option" and this VI start to execute, my primary loop stop. It is normal than only the VI on the top window can run and it stop all the loop in the caller vi.
 
Thank you
 
Jacomino
 
 
 
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In my attempts to work with wi-fi on the PDA I remember setting up my applications to send a "ping" every 15 seconds or so just to make sure that the connection is still alive. If I remember correctly, though, the application would function normally without this and I think I even saw one time where a connection reference continued working even after the PocketPC automatically shut down and had to be turned back on (including wi-fi). I would make sure that you don't have some sort of low power mode set on your wi-fi connection.

As far as I remember, a GUI VI should not stop other loops, but I never did look into this thoroughly. Is it possible something else is making your loop get stuck (like trying to enqueue an element into a full queue or maybe trying to open a second window in the other loop)?


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I make a new project to prove the behavior of my loops. See the diagram here http://community.webshots.com/myphotos?action=showPhoto&albumID=549074909&photoID=298492284008831614...

When i call the VI, and i wait for example 10 second and i close, the indicator of loop 1 could be higher than 10 count than the indicator loop 2. It is not. The count are equal. The loop 1 is lock by the call.

I read in "PDA module user manual" http://www.ni.com/pdf/manuals/370624b.pdf  page 5-5 at Hierarchical Limitations, "Because of the differant application structure on PDA devaices, PDA VIs always start form one top-level VI and complete when that top VI complete.  bla bla ..you can not start and run multiple top-level VIs simultaneously.  I can't believe this explanation explain my behavior. If the Labview PDA work like this, it is worse than Labview 2.0

Please help me because with this limitation it's very difficuclt to make an application. I must be make ONE large VI with controle visible and invisible and i hope the PDA can support a large VI 

 

 

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That does sound weird - I would expect that unless the VI called in loop 2 has no wait in it and takes up all the CPU time then loop 1 should proceed normally (and that it should even the VI doesn't have a wait in it). I have definitely wrote VIs with multiple loops in the past where one of the loops opens a GUI VI and the other loop (a communication loop) keeps running and I don't remember having problems with it (although those were only demo VIs). Maybe it's a problem with LV 8?

I suggest you upload an example here that people will be able to test (there is a field to add attachments under the posting area, and make sure you don't preview the post).

Anyway, on the note of LV PDA being worse than LV 2, that's quite possible - LV PDA is still quite buggy and is missing a lot of functionality found in the desktop version - I suggest you go through the posts here and on the LAVA forums and if you see anything that would affect your application or if you need to write a large application consider using other tools.


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Hello,

 


I believe that the problem you are experiencing is probably related to the fact that the PDA module is not multi-thread capable.  This would mean that while execution is in the wait function, the bottom loop will not execute (similar capability for multiple VIs).  It’s not so much that the PDA module is “worse than LabVIEW 2” as the PDA OS, processor, and memory limit the performance of applications.  If this weren’t the case, the PDAs would all run Windows XP and we could just all run LabVIEW 8.0 Pro on them.  The PDA module is designed so that you can write small LabVIEW programs for use on highly portable platforms such as PDAs.  For your application you might want to consider writing code that executes to keep your connection alive (similar to the recommended ping suggestion earlier).

 


Hope this helps – please let us know if you have other questions!

Travis M
LabVIEW R&D
National Instruments
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During the discussion, i reveived a message from NI. Voila

>Thanks for contacting National Instruments. This actually is expected

>behavior. LabVIEW PDA does not support multithreading (even if the

>operating system does), so whenever a new front panel opens, the active

>thread switches until the new activity completes. Unfortunately, there

>is no good way to force the threads to operate simultaneously. So you

>may just want to refrain from using subVIs for code that must execute

>concurrently.

>

>You may want to submit a product suggestion for this feature

>(

http://digital.ni.com/applications/psc.nsf/default?openform). These

>suggestion go straight to R&D so they are an excellent way to get your

>feedback directly to developers.

Like you see, it 's Labview PDA does not support multithreading. Fortheremore, i remember  Win95 with Labwiew 2.2 it was not multithread (even the operating system) but it can run parallel loop with calling VI. But i will make the suggestion for Labview PDA.

For the moment, i programming my appllication in one big VI. My diffrents Window is differents Tabs containing my controls and indicators wich appears and disapears with a loop ping the TCP-IP.

Thank you at all for your help

Jacomino

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