HELP! - VISA read Error BFFF003E

[R Hibbert]

I have a serial app that keeps hanging on VISA read if it tries to read the remote device when the remote device is powered down and (so far) I am unable to recover from this.

The only reference I can find is by using Google. At http://zone.ni.com/devzone/conceptd.nsf/webmain/72C6FC6CE4AD4D1386256B1800794596?opendocument it says
-1073807330 (BFFF003E) - VISA "Could not perform operation because of I/O error"
or
LabVIEW hangs with Serial Write compatibility VI

Generally, these problems mean that lines 11 and 12 have not been properly grounded. You should be able to jumper these lines to any of the ground lines (18-25). Make sure you have not accidentally grounded lines 2 and 3 by mistake.

but this is in reference to a Parallel port. Can somebody provide a work around?

Thanks

[Dennis_Knutson]

VISA is supposed to return an error if you don't have the device powered up. You can minimize the time that VISA takes before returning the error by setting the timeout value. This is done with a VISA Property Node (Prperties>General Settings>Timeout). Then when you get the error, you will have to add some code in your program to trap it. Once powered up, what problems do you see when trying to rerun your program?

[R Hibbert]

Thanks for your reply. The PC I am running the vi on is (obviously) powered up. If I power the remote device down, then I get this error. However, when I power the remote device back up, I am unable to resume communications. The only error I log is this one. There is no hardware nor software handshaking in this protocol.

In the cold light of day, I think that the problem is with my VI as I am using shift registers to remember the previous Error. I guess I need to come up with a schema for resetting the error.

I've attached my code for your comments.

Richard

[Dennis_Knutson]

What I would suggest is adopting a state machine architecture. There's a couple shipping examples and more on the Developer Zone. With this, you can easily jump to an error recovery state where you would first prompt to turn on the external instrument and then reset the error cluster.

[R Hibbert]

Thanks. My mind wasn't working too clearly at 4am!

Richard