VISA Write timeout with GBIP

[Marc_A]

We have an old HP 8753B Network Analyzer that is connected through GPIB. I'm trying to get it working with an example included in the drivers found on NI's site. Communication is working, the initialize VI and a save/recall state VI both execute fine. However, the next VI to run simply sends one command which is only 5 characters long to VISA Write. This Write will timeout after 10 seconds and return a "Timeout expired before operation completed" error.

Any idea what would cause this half way through an example program? I've been searching and I see things about sending large amounts of data causing this error, but we're only sending one small command.

Also, there used to be a different VI before the current one that causes a problem and that would return the error. It seems as though anything that follows the save/recall state VI fails.

I don't know much about GPIB, but I'm thinking that the save/recall state VI is somehow making the instrument hang up and then when I call VISA Write in any VI afterwards, the handshaking that is supposed to occur fails. Does this make sense?

[mfitzsimons]

I would remove the, "seems as though anything that follows the save/recall state VI fails."  It maybe recalling a state that doesn't exist or the model number / options installed in the physical equipment doesn't support this feature.  I would stick to more general commands like simple configuration and get current value.  Drop a probe on the error pins going in and out of the VI in question.  Hope this helps!

[Marc_A]

Thanks for the reply, but I just figured it out. It turns out there was a VI in that save/recall state that opened another VISA session to send some commands, then closed it. For what reason, I have no idea. These drivers weren't coded very well. I took that out and now it works fine.