serial communication

[sravan-arp]

Hello,

I am using 4 COM ports to communicate with different instruments in a single application

COM1,COM2 and two PL2303 USB-Serial Converters COM3,COM4

Sometimes,when launching the application I can't data from few instruments

When I open VISA session of particular port, error "VI_ERROR_RSRC_BUSY -The resource is valid but VISA cannot currently access it" appears.

COM1,2,3 works fine and COM4 shows error or COM1,2,4 works fine and COM3 shows error. I am unable to predict which stops communicating at what time.

Why is it so? How can I access data from all ports? The port properties are set correctly and I gave approriate delays between each poll

Please help me regarding this

Thank you

[Sean.C]

I have had the same error previously, but I don't know if you are having it for the same reason. 

In my case, it has happened when I open a connection with one program, vi, sequence, etc. and then attempt to open another connection using the same port with another subvi/sequence/etc.  This can happen especially in labview because processing runs in parallel.  I would check to see if you are having a race condition occurring where you try to access COM3 or COM4 when it has been opened (but not closed) by another subvi or program.

I hope this was helpful.

[sravan-arp]

Thank you

The problem is due to one instrument connected to COM3.It takes long time to release the port!!!

Any how problem is solved.Thank you