VISA viFindRsrc with NI/Agilent Interfaces Returns Invalid Resources

[Ross Welu]

I'm testing an application using VB.Net and the VISA32.dll with multiple GPIB Interfaces (NI GPIB-USB-A and Agilent 82357A). I have enabled the NIVisaTulip.dll - VISA Library Passport for Tulip so that I can use NI VISA to communicate with the Agilent Interface.

The first call to viFindRsrc using a search expression of ?* normally returns the actual instruments on the bus for both interfaces (named GPIB0 for the NI interface and GPIB1 for the Agilent interface). However, subsequent calls return both the valid resource descriptors and, in addition, invalid resource descriptors for all other possible GPIB addresses as follows (first three are valid):

GPIB1::INTFC
GPIB1::4::INSTR
GPIB1::28::INS
TR
GPIB1::1::0::INSTR
GPIB1::0::INSTR
GPIB1::1::INSTR
GPIB1::2::INSTR
GPIB1::3::INSTR
GPIB1::5::INSTR
...
GPIB1::30::INSTR

Running the VISA Interactive Control from NI MAX provides the same results.

Calls to viOpen with these invalid resource descriptors do not return an error and appear to open a valid instrument session.

Is this a problem in the Tulip layer and how can I identify valid resources?

[Dan_Mondrik]

Ross:

What version of the Agilent I/O libraries do you have installed? If your version is older than K, you should upgrade.

In the case where you use the NI TULIP Passport, we pass all VISA calls through to the Agilent library. So I have no idea why their driver is returning all those invalid resources. You should contact them if upgrading does not solve your problem.

Dan Mondrik
Senior Software Engineer, NI-VISA
National Instruments

[Ross Welu]

Dan,

I have version L of the Agilent I/O libraries. Since posting this question, I have tested Agilent VISA as the primary visa (sicl32.dll in the Windows System directory is Agilent's). It no longer returns all addresses as instruments although it does have one problem. It recognizes the NI interface as another instrument. I can filter this out by eliminating instruments with the same primary address as the interface. Since the Agilent VISA is providing more stable results, do you think the problem could be in the NI layer?