VISA-Find-Resource returns nothing.

[Dave123]

Hi,

(I'm using LV7.1 on a G4 Mac running OSX v10.3.9)
I created a vi with the "VISA-Find-Resource" function in it. I set the input expression to "*?" to return all found i/o resources but nothing is found and the return count is zero.

Should I see all the USB devices connected such as mouse and keybourd and other I/O devices?

Is there another function I have to use before VISA-Find-Resource to initialise it or something like that? Or is there something I have failed to install for it to work?

Thanks for reading,
Dave.

[Dennis_Knutson]

The search parameter *? is illegal and you should be getting an error with that. Use ?* instead.

And no, your USB mouse, keyboard, etc. will not be listed. No USB device will be listed unless there are VISA drivers for them, like a USBTMC instrument.

[Dave123]

thanks for your reply.

Sorry that was a typing error, I am using '?*' after all.

So are VISA functions only for external devices that are recognised as known instruments?

If so is it possible to get LabView to communicate with a USB device that's not recognised as an instrument and how?

Thanks.
Dave.

[Dennis_Knutson]

I keep hoping that someone with Mac experience will see your posts as I only ever worked with Windows.

Let me start with some of the basics of USB devices. Under windows, there are several inf files that come with the OS and they allow for automatic detection of certain types of USB devices. For example, there is HID type inf file that Human Interface Device types such as keyboards and mice will use. Other device will install their own inf file so that windows will recognize it. Under windows, to communicate to a USB device with LabVIEW, you would use whatever low level driver is provided by the vendor. This would normally be done with the Call Library Function Node to interface to the vendor's dll that they provide. In one of your other posts, you reference a tutorial on using VISA with a USB device. You use the VISA Driver Development Wizard to create an .inf file. In windows, an inf file is how the USB device is identified to the OS and the file created by the wizard tells windows that VISA  is the interface to the device. You would then use the VISA RAW functions to send/receive data. However, the inf file is only supported under windows as far as I can tell but I could be wrong.

Have you tried to contact the vendor of your device to see if they have anything for the Mac?

[Dave123]

- thanks for that.

Yes I contacted the vendor but unfortunatly they only seem to be able to advise on PC interfacing.

I'll keep trying.

Regards,
Dave.