USB-6501 command set

[J^T]

Hello,

I'm considering talking with a USB-6501 via NI-VISA. I assume the USB-6501 is a USBTMC device, and supports some type of IEEE 488.2 command set.

Where can I find the command set USB-6501?

Thanks,

--J^T

[Dennis_Knutson]

As the Data Sheet states, you use NI-DAQmx. Originally it was only supported by the base version but since DAQmx v7.5 was released, you can use the full version. The latest version of DAQmx is v8.

[J^T]

Dennis:

Thanks for the reply.

Yes, I know about DAQmx, but it doesn't fit my application. (It's a control application, not a traditional DAQ application.) I need to talk to the device without DAQmx in the middle, thus the reason I'm using VISA.

VISA is the right software architectural level, but now I need the USB-6501 command set. This should be documented somewhere, but I don't see it.

--J^T

[Dennis_Knutson]

So you want to put VISA in the middle and use USB raw? I think your only hope is the DDK but that's an awful lot of work for zero gain, imho.

[Malcolm]

We do not currently have a DDK for the USB-6501.  The complicated part is documenting the internal communications protocol.  It does not conform to the USBTMC standard or use SCPI (IEEE-488.2) style commands.  It instead uses VISA Raw to communicate at a very low level.  The best option would most likely be to use NI-DAQmx (as Dennis mentioned).

I'm curious why NI-DAQmx does not fit your control application.  What is it that you are trying to accomplish?  How many of these devices are you using?  Are you just trying tom use a simpler programming interface?  Is the rest of your system using GPIB-style commands?

[MarcVB]

I am also looking into the purchase of USB-6501 but I also want to program it via VISA USB. The reason is mainly because I want to integrate it into an instrument that has its own PC with a LAN connection. It should be possible to address the USB-6501 from an external PC through that LAN connection in a transparent way (same software as on the internal PC). The idea was to go via VISA LAN, in a similar way as one can control GPIB instruments via LAN, having the LAN as a transparent communication,

Marc Vanden Bossche

NMDG Engineering

[J^T]

Thanks to MarcVB for resuscitating this thread.

I've been unable to use the device I purchased from NI because of the lack of an appropriately light-weight API. Fortunately, this aspect of project has been set aside until January. I'd be more than happy to drop down and code to the raw USB level (OS or VISA), if only the command set was available.

Has any headway been made on documenting the USB-6501 command set?

The fall back is to reverse-engineer the command set using a USB bus sniffer, but I'd hate to do that simply because NI won't share its doco. I'll take it in any form y'all have it -- "as is", unsupported, unofficial, "you didn't get it from me", "don't come crying when you smoke the device", etc.... 🙂

--J^T

[Jennifer O]

Hi J^T,

Malcolm's post is still valid;  USB currently is not supported under MHDDK (Measurement Hardware Driver Development Kit).  I invite you to submit a product suggestion here, which will help to show the demand for USB DDK support.

 For information and support on DDK, visit the DDK discussion forum.

Regards,

Jennifer O.
Applications Engineer
National Instruments

[MarcVB]

One of the reasons why I am looking into using VISA USB with this digital I/O is to use the same software on a remote PC and to be able to access still the digital I/O connected to the other PC by adapting the VISA resource, similar as talking to GPIB instrument through LAN.

Does DAQmx give this possibility? Suppose I use this do develop my code ... is it "easy" then to still access the digital I/O but from a remote PC through LAN by changing something similar as resources? ... I am ignorent about DAQmx .. If this is possible, this would be a solution for us.

[Jennifer O]

Hi MarcVB,

With DAQmx 8.0, the ability to use OPC to communicate with DAQ on a remote machine was introduced. See Using the LabVIEW Shared Variable and OPC With NI-DAQmx for instructions on how to set up communication.  In LabVIEW 8.0 (or later) the shared variable can simply be read to retrieve the data from the remote computer, however LabVIEW is not required.  You can also use a third party OPC client to connect to the variable engine server. Developing an OPC Client Application Using Visual Basic is a good resource to reference for creating an OPC client in a text based language.

Hope this helps,

Jennifer O.