VISA Alias vs. "Dev1" in NI-DAQmx Base

[BARMatt]

Using C++ with VISA and NI-DAQmx Base v1.4, how can I detect what I should address a connected device by when creating tasks ala "Dev1/ai0"?

The NI-DAQmx version of the interface I'm writting just used DAQmxGetSysDevNames to just easily but, sadly, that function doesn't seem to have a NI-DAQmx Base equivilent.

I've used VISA to detect the long name ("USB0::...") and the alias ("Bob", "DoohickeyOnMyDesk" or whatever) but they don't seem to work. So how do I discover "Dev1" or whatever it is for the particular user's device that I need for the channel string?

[Nealgres2]

I have the same problem in LabView i would like to use the visa information to detect but that seems to be a problem.

[AlanArmstead]

There is a program that installs with NI-DAQmx Base that will list all DAQmx Base devices. In windows, it is called DAQmx Base List Devices. In Mac and Linux, it is called lsdaq. If you are curious about finding out devices present programmatically, there really isn't a great way to do this. One solution that several customers have used in the past is to loop through several device numbers calling a function like DAQmxBase Reset Device, then look at the error code returned. If the device number doesn't return an error, then the device number is valid. Again, this isn't an ideal solution, but it works.
-Alan A.

[WM_John_Weeks]

This brings up an obvious question: how does lsdaq do it?

[BARMatt]

If you are curious about finding out devices present programmatically, there really isn't a great way to do this.

So I've noticed, with great sadness and moderate frustration. 😉

The List Devices utility you mentioned turned out to be pretty handy when used with NI Spy. I tried that first and was able to figure out how to get the alias pretty easily by accessing an undocumented attribute but I didn't see anything obvious that indicated "Dev1" was the device name even though it was displayed as such. Can a user change that name to anything they want like with DAQmx devices or will it always be "Dev-"?

[AlanArmstead]

I am not aware of any way to change the device name in NI-DAQmx Base. I believe this to be a limitation of Base.
-Alan A.

[BARMatt]

If that's the case then that would actually be helpful because I could do the name looping you described with Dev1 through X. Still, I hope mxBase v1.5 has DAQmxBaseGetSysDevNames implemented. 😉 Thanks for the tips, I think I'll be able to work this out now.

[AlanArmstead]

If anyone is intersted, here is a LabVIEW VI that lists all NI-DAQmx Base devices programmatically.
-Alan A.

[WM_John_Weeks]

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@Alan A. wrote:
If anyone is intersted, here is a LabVIEW VI that lists all NI-DAQmx Base devices programmatically.
-Alan A.

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Very interesting, Alan. I don't use Labview; can you describe what your VI does? Would it be difficult to implement it using the DAQmx Base C API?

[AlanArmstead]

John,
The answer is yes, it would be extremely difficult (probably impossible) to implement this with the C API. As you probably know, NI-DAQmx Base is written in LabVIEW, and this program uses quite a few VIs that do not have C API function equivalents. A possibility would be to build a dll from the LabVIEW program and call that dll from your C program.
-Alan A.