Problem with instrument driver (HP37717c)

[rooo]

I have Windows 2000, Lab View 7.1, and PCMCIA-GPIB card (by MCC). I want to communicate with HP37717c analizer.
GPIB interface seems to work properly, althouth MAX didn't find it, because it wrote that PCMCIA-GPIB interface is plug & play. I can communicate with analizer using the program supported by MCC or LabView GPIB example. But whenever I try to use any of VI's in hp3771x directory, the same error occures:

Driver Status: (Hex 0xBFFF0011) Insufficient location information or the requested device or resource is not present in the system." The hexadecimal number may vary.

The resource name is correct.

I read that I needed both LabView wrapper and VXIPlug&Play Instrument driver. So I have them both and I tried to i
nstall it in many ways.

There's something more. I've added the instrument using MAX (GPIB-VXI0::5::INSTR) and MAX couldn't open VISA session. It probably has smth. to do with my primary problem.

Can anyone help me to solve it? I'm a novice, so try not to coplicate your answers too much;) Thanks.

[Dennis_Knutson]

MAX will not detect any boards from other manufacturers. It is a NI utility program and should not be expected to work with anything else. I'm actually surprised that the LabVIEW GPIB example worked. That must mean that MCC copied all of the NI commands and implemented them into their hardware (if they didn't actually copy the hardware itself as well). In order for a driver that uses VISA to work, the GPIB board vendor must provide a VISA driver for their hardware. If the vendor does not have one, you have to convert any driver that you download, to use the functions that the card supports.

[rooo]

I thought that this is a problem with instrument drivers. I've been assured, that the board works correctly with LabView and I don't need any additional driver for it.

Can you write me what do you thing I need to communicate with HP instrument by MCC GPIB board?
You wrote smth. about converting drivers that I download. How to do this?

[Dennis_Knutson]

Measurement Computing isn't telling you the whole truth. It may work with the LabVIEW GPIB primitives or with GPIB functions that they provide but all new instrument drivers use an API called VISA and all makers of GPIB cards should provide a VISA interface. VISA is fairly old now and is a more portable driver interface. With VISA, you can write a single driver that will work with a serial, GPIB, VXI, USB, TCP/IP communication buses. You can buy a lot of instruments with optional buses and VISA makes it easy for the author of the driver to support everything. By saving a few dollars on the hardware, you've gotten into the situation where instrument drivers that you download from NI, Tektronix, Agilent, etc. won't work without a lot of mod
ification. What you will have to do is replace every VISA Read/Write in the instrument driver with the functions that come from MCC.

[rooo]

O.K. Now I'm totally lost. Here are some other problems I've noticed and questions I need to ask.

1. Now I don't know if I really can communicate with this instrument. Sometimes I do, sometimes I don't. I can send FindLstn command and it responds (but not allways) [pict. 1. and 2.], but I get no respond if I send *IDN? for example.
2. If I send a SCPI command with some instrument settings [pict. 3.], I suppose something should change on the instrument's screen. And nothing happens.
3. You wrote about replacing VISA functions. So I've checked it and it turned out that there aren't any VISA functions in hp3771x instrument drivers. There's only something called 'IVI session' [pict. 4]
4. MCC doesn't support any functions that I could use in instrume
nt drivers. Where should I look for it?
5. And the most important question. Are u sure, that if I replace the MCC board with a NI one, my problem will be solved?

Thanks for your help

[Dennis_Knutson]

I'll try to explain and hopefully not confuse you more. First, I didn't download the driver and wasn't aware that it used IVI so I apologize for that.

IVI stands for Interchangable Virtual Instruments. It is an instrument driver standard established several years ago by NI and several other instrument manufacturers. IVI.org established several instrument classes (i.e. DMM, Scope, FuncGen) and determined a set of common functions. By using the class driver, the idea was that a user could switch instruments without having to modify the program. An IVI driver is a DLL written in C (LabWindows/CVI) and is popular because the DLL can be used in any programming language. Every IVI driver is required to use VISA to do the actual communication
with the instrument. IVI drivers can be valuable in some situations but because they are written in C (and not everyone makes the source code available anyway), you cannot modify the driver in LabVIEW. All of the IVI functions you see in your driver are nothing more than wrappers to a Call Library Function. If given the choice, I will almost always use a native LabVIEW driver over an IVI driver simply because I want the edit capability if the driver doesn't do all that I want. What this all boils down to is that you will never be able to use the driver with the measurment computing board unless they can provide a VISA library.

I can't state with 100% confidence that you won't see any problems with an NI board but the chances are real good. They were driving forces in the establishment of the standards and their software is usually used to create the driver. Maybe your local sales rep has a loaner that you can try before buying. I'm sure he or she would love to prove why their hardw
are is better than measurment computing's.

[gagi1]

This particular driver is not an IVI driver. It is a LabVIEW wrapper for an VXIplug&play driver that Agilent provides on their web site. Since it is a wrapper and not native LabVIEW code, the diagram cannot be modified.

However, the main problem seems to be that you are not able to communicate with your hardware using VISA. The best way to check that would be to eliminate the driver layer and go strait to the VISA Interactive Control (VISAIC) (Start>Programs>NI>VISA). If your card works with NI-VISA, it should show up in the list of resources in VISAIC. Then you can double-click on it and try to use Basic I/O. If this doesn't work, then the driver is not going to work as well. The problem can be in your VISA installation or in the fact
that the card does not work with NI-VISA. As Dennis suggested, you can contact NI sales rep in your area and he/she should be able to provide you with a loaner that you can try before buying a NI card.

Regards,

Vesna Jadric
Instrument Drivers/IVI
National Instruments