multithreading RS232 labview

[Sadok]

Hi every body,

I have to develop an application that execute 16 threads in which I communicate with 16  device via RS232 . I use a Multi port card NI8430/16.

Is that possible with labview. Can it work in parallel. I have no idea about multithreading. Can you give me an example. the pc, need it any special configuration.

Thank you for help it is very urgent

[PRCalDude]

Can't you just create 16 of these and then read and write from each?

[NAKeel]

LabVIEW is definitely capable of multithreading.  All of the threading is handled internally in LabVIEW.  I think that PRCalDude's recommendation is a good one. 

[Oskar_Bosch]

I think this vi (visa serial) is not re-entrant. Hence you would not gain much with creating sixteen. I would check into the actual lower level VISA functions and see if those are re-entrant. Otherwise all the threads would be just waiting for the other to finish.

[NAKeel]

Oskar is definitely right.  The visa serial is not re-entrant by default.  The following KnowledgeBase addresses this issue:

Accessing Serial Ports Using Parallel Execution Hangs My Program Intermittently in LabVIEW

http://digital.ni.com/public.nsf/allkb/59458684CF7861CC862565410061DB3B?OpenDocument

[RavensFan]

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Oskar Bosch wrote:
I think this vi (visa serial) is not re-entrant. Hence you would not gain much with creating sixteen. I would check into the actual lower level VISA functions and see if those are re-entrant. Otherwise all the threads would be just waiting for the other to finish.

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Correct, the VISA configure VI is not reentrant.  But so what?  That VI should only be called once per port at the beginning of the code.  And it would not take long to run anyway.

You don't even need to use that VI.  It is just a wrapper for setting a bunch of property nodes for the serial port.

Message Edited by Ravens Fan on 05-29-2009 04:51 PM

[PRCalDude]

Hmmmm.... I can definitely see myself running into that problem in the future.  Thanks. 

[Dennis_Knutson]

Reentrancy is not even relevant. That KB article that Nick posted was written in 1997when there were separate serial functions. Now, all serial functions are VISA. The article on synchronous/asychronous would be more relevant to this discussion.

Message Edited by Dennis Knutson on 05-29-2009 03:13 PM

[Oskar_Bosch]

Good article regarding the synchronous versus asynchronous. Seems useful for everyone to read.

[Sadok]

Thanks for all!