Discussion:
VISA and virtual GPIB on Tektronix oscilloscope
(too old to reply)
maxim morozov
2006-03-15 22:14:06 UTC
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Hello,

Is there any way to control a Tektronix-Windows-based-oscilloscope TDS5000 locally via NI VISA API, or the only ?Open Choice? is the TekVISA?

If yes, how do I configure the "virtual GPIB" resource GPIB8::1::INSTR in MAX?

Thank you for eventual help.

Regards,

Maxim (***@unicas.it)
AlessioD
2006-03-16 07:11:36 UTC
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I see that scope has been discontinued by tek. I am not that familiar with the specific instrument, but I don't see any big problem that would prevent NI-VISA from recognizing the scope and working with it.
I don't actually know what kind of physical interface the instrument offers for connectivity with PCs. Is it an ethernet port or USB? Since you were talking about a "Virtual GPIB" resource, I guess the tek must have something different from a GPIB port to connect to.
Suggestions

- browse to the <a href="http://www.ni.com/drivers" target="_blank">www.ni.com/drivers</a> page, click on the Download button to the left and search for a suitable driver for your instrument

- browse the tek web page and see if they still offer an instrument driver for that instrument. If it is IVI compliant (look <a href="http://www.tek.com/site/sw/detail/1,1059,3482,00.html" target="_blank">http://www.tek.com/site/sw/detail/1,1059,3482,00.html</a>) then it is likely to have a .fp file in the driver. The .fp file is a library file that can be used directly in CVI or imported in LabVIEW (Tools&gt;&gt;Instrumentation&gt;&gt;Import CVI Instrument Driver).

- you reported a specific resource that appears to be GPIB8::1::INSTR. This is already a VISA resource. So from LabVIEW, when browsing for VISA resources, you should see this.

AlessioD
maxim morozov
2006-03-16 10:41:30 UTC
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continuation

&nbsp;

3) I uninstalled the TekVISA and installed NI VISA 2.6. Now the serial port works better.

What does not work is ? as you have already guessed ? the interface with the TekScope application. The reason: VIASA error -1073807195 : ?The interface type (GPIB8::1::INSTR) is valid but the specified interface number is not configured?. It looks pretty like ?no TekVISA ? no virtual GPIB?.

&nbsp;

4) I tried to ?configure? the resource GPIB8::1::INSTR in MAX, however it is not a real GPIB, so it is not found (even when the ?TekScope.exe? application runs), and I did not succeed with GPIB-VXI neither.

&nbsp;

5) All other ?Open Choice Solutions? offered by Tektronix (IVI driver and VXI driver, even ActiveX connection to the TekScope.exe with ProgID TekScope.TekScope.1) demand the resource GPIB8::1::INSTR.

&nbsp;

6) Therefore the QUESTION arises: is there any way to control a Tektronix-windows-based-oscilloscope locally via other vendor?s VISA API (for instance NI), or the only ?Open Choice? is the TekVISA?!

&nbsp;

7) I believe the NI can answer this question easily since they supply various ?add-ons? for the Tektronix, hence should know the problem very well (unless there are voodoo or Chinese horoscope involved).

Thank you for eventual help.

Regards,

Maxim (***@unicas.it)
maxim morozov
2006-03-16 10:41:30 UTC
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Dear AlessioD,

Thank you for advise.

I shall try to explain the problem with TekVISA (not only I have encountered it, see NI forums and Tek?s website) in more details:

&nbsp;

1) An oscilloscope Tektronix TDS5104B (as all the series from 5000 and higher) is Windows2000-based (practically a PC with a modular digitiser). The oscilloscope software part is ?TekScope.exe? application. Tektronix supplies a TekVISA API as well. When the application runs, it exposes a so-called ?virtual GPIB? resource (GPIB8::1::INSTR) which is not visible by a VISA resource manager otherwise (that is when the ?TekScope.exe? is off and the machine works as a PC).

&nbsp;

2) In this configuration, I can transfer waveforms to other programs (from TekScope.exe to LabVIEW, for instance) &nbsp;running directly on the local machine -&nbsp; the scope - via the TekVISA API addressing the ?virtual GPIB? (GPIB8::1::INSTR).

However TekVISA works rather poorly (especially with other resources such as a serial port), plus LabVIEW does not explain its errors (since errors of TekVISA have not been included into the respective database) and I cannot enjoy all the ?cool features? of NI resource manager.

&nbsp;

continues ...
ScottieB
2006-03-17 15:41:43 UTC
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Is the Tek documentation you're referring to for communicating to the scope from ANOTHER PC or from the Tek "PC"?&nbsp; From what you've said above, it appears that you're trying to communicat via "virtual GPIB" from the Tek scope itself.&nbsp; I think Tek's documentation is talking about communicating with the scope remotely, in which case NI-VISA would work just fine.&nbsp; It's the "virtual GPIB" part that I'm pretty sure NI-VISA doesn't understand.&nbsp; You're basically telling NI-VISA to go open GPIB8, hardware that isn't on the system.&nbsp; NI-VISA has no knowledge of Tek's "virtual GPIB" setup as far as I know.&nbsp; You can't configure virtual GPIB in MAX--it's a Tek thing.&nbsp; Thus, I think the Tek VISA passport as GPIB Guru suggests might be a good thing to look into.
&nbsp;
VISA passports are the software layers that allow VISA to understand various interface types when you pass it a resource descriptor.&nbsp; Thus, theoretically, if Tek had a "virtual GPIB" passport and you enabled this with NI-VISA, NI-VISA could then talk to the virtual GPIB port.&nbsp; This is a longshot--I don't know if Tek has anything resembling this.
&nbsp;
Scott B.
GPIB Software
maxim morozov
2006-03-17 16:42:06 UTC
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Yes, I do network with the scope application locally - on the scope machine.
Tektronix' support says that "virtual GPIB" is a resource which enables to send GPIB-syntax commands via PCI bus from the DSP processor&nbsp;of the digitiser hardware&nbsp;to the system processor of the PC side of the scope. Therefore one MUST use the TekVISA, they say.
From the System&gt;Device Manager I can actually see :
1) Tektronix IO processor
2) Tektronix PCI acquisition interface
However I don't know how it can be useful.
I have send a request regarding TekVISA passport to Tek. Waiting for replay.
Regards,
Maxim
maxim morozov
2006-03-22 10:10:14 UTC
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Well, it is getting pretty confusing an affair. First, Tek makes an impression that TekVISA is indispensable. Now I found the following (readme-file for TekVISA by Tek):

1) Two distinct implementations of Virtual GPIB are provided: for NI-VISA version 2.5 or newer and for version 2.0 of TekVISA.&nbsp; In both cases, the Virtual GPIB resource is opened via the resource string ?GPIB8::1::INSTR?.

2) &nbsp;The Virtual GPIB resource for NI-VISA 2.5 is a passport DLL.&nbsp;

&nbsp;

And Tek support writes:&nbsp;?TekVISA includes NI Passport.&nbsp; That is an important componenttowards simplifying TekVISA with NI applications and NI-VISA with Tekutilities, however, it is not the answer to complete inter-changeabilityof the VISA systems on all PCs and Windows scopes?.

&nbsp;

Well, when I use NI VISA 2.6 and type ?GPIB8::1::INSTR? into VISA resource, I get error: ?The interface type (GPIB8::1::INSTR) is valid but the specified interface number is not configured?.&nbsp;&nbsp;How do I configure it? Or I've got a wrong "implementation of Virtual GPIB"? And why should I care whether TekVISA includes NI Passport, if I don't want to use TekVISA?

Advise, please.

Thanks,

Maxim
maxim morozov
2006-03-24 16:40:13 UTC
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All right, I've done it: replaced the TekVISA by NI-VISA and still able to interface the scope application via VIRTUAL GPIB. The key point was: not to uninstall the TekVISA, but to overwrite VISA32.DLL with NI-VISA. Now there are no problems with the COM port. Apparently the "passport dll" remains visible to NI-VISA (not to me, though).
Given that the magior part of the posts here are mine, it is rather a Blog than a Discussion Forum. I am very disappointed that NI didn't contribute. Since long time I have the feeling that NI has got a Microsoftish attitude towards their users: difficult to get a transparent help (instead of "open here and click there"). Perhaps, they've got too strong a leading position on the market. Maybe it's better to drift to another producer, to refresh the competition.
Sincerely,
Maxim Morozov
maxim morozov
2006-03-24 22:40:13 UTC
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XBAND wrote: ?I was able to talk with normal visa commands of LV7.1 by using the USB connection.&nbsp; I'm communicating with a Tek DPO4000, which has the Window's 2000 operating system. My only problem is getting data with more than 10k points.&nbsp; The scope has a setting for up to 10M points, I cannot get more than 10k through this communication , maybe it times out, but its funny that it is always 10k.?

&nbsp;

- The limited number of waveform points possible to transfer from a digital scope is a usual problem for Tektronix as well as LeCroy windows-based scopes (perhaps unless classic GPIB is used).

I am afraid the reason is that their VISA (respectively XStream on LeCroy) API implements an object-model for the scope and the Microsoft COM (component object model) does not enable the ?variant? variable to accommodate too big an array. Again, the producers should know, however they keep quiet on the details.

Regards,

Maxim
maxim morozov
2006-03-24 22:10:13 UTC
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To GPIB Guru: I&nbsp;conclude that NI did not contribute to resolving the given problem since:

1) there hasn't been a replay signed by a "NI engineer" which would give me an unambiguous instructions;

2) I have sent an e-mail to NI support with a request for assistance more than a week ago and haven?t receive a response.

Regards,

Maxim
Ed Christy
2007-08-22 17:10:13 UTC
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I created an executable from LabVIEW 8.2 to run on a Tektronix 7254 scope.&nbsp; Among other things, this application essentially acts as a server for a remote client on a standard PC.&nbsp; The client sends high-level commands to the server which then manipulates the scope as needed, i.e. setting it up and retrieving waveforms for the client.&nbsp; This requires using the LabVIEW VISA read and write VIs and the VISA device GPIB8::1::INSTR.&nbsp; Building and debugging the system was done on a PC.&nbsp; Communicating with the scope was done over TCP/IP through the VXI-11 server on the scope.&nbsp; I just did a standard installation of tekvisa on the PC and didn't touch the scopes.
After getting the application to run correctly on the PC, I compiled it and ran it on the scope.&nbsp; This caused all sorts of problems.&nbsp; The most notable of which was that my application seemed to be chewing up a LOT of processor time, even slowing mouse movement.&nbsp; When the scope was armed in fastframe mode, a thread was monitoring the trigger/acquisition state with a 500ms loop time.
I created a very simple application which I ran on both the scope and the PC.&nbsp; It was just a simple user interface that allowed me to post commands from the keyboard.&nbsp; I still saw a difference in execution.&nbsp; I sat down with Chris Burak from Rio Scientific in Albuquerque.&nbsp; By using the Open Choice call monitor on the scope, we were able to analyze the visa function call sequence created by a simple *idn write and read.&nbsp; We discovered that executing the command on the scope produced a different sequence than when run on the PC.&nbsp; Most notably when run on the PC, a synchronous read was executed.&nbsp; The same command on the scope executed an asynchronous read.&nbsp; We found that the LabVIEW VISA VI's can be set for synchronous or asynchronous mode.&nbsp; They default to asynchronous mode.&nbsp; Right-click on the VI and the mode can be changed.&nbsp; When we recompiled the original application with the VIs set for synchronous operation, it ran on the scope as it did on the PC.
I was told by a Tektronix applications engineer that the GPIB8::1::INSTR call is also routed through the VXI-11 server.&nbsp; If this is true, it certainly treats it differently than a TCP/IP call.&nbsp; VXI-11 must alias the commands to always do a synchronous read when accessed through TCP/IP.&nbsp;&nbsp; I hope this helps.Message Edited by Ed Christy on 08-22-2007 11:53 AM
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