How to count number of NI digitizers installed [NI-DAQmx Base]

[john.clements]

I'm the author of a cross-platform scientific data acquisition/analysis program (C++ using Qt: Windows and OS X). I'm just getting started on adding support for NI digitizers. It's tougher than I was expecting - there's so few helpful code examples. On Mac OS X I'm stuck with NI-DAQmx Base. I'd be very grateful if someone could help me with a couple of basic questions...

1) How do you determine if the computer has an NI digitizer installed?
1a) Is there a way to count the number installed?

2) How do you synchronize things so that the input and output streams start at the same sample point?

Thanks,

John.

[David L.]

Hi John,

DAQmx base does not have property nodes, therefore we cannot programmatically determine information about the cards. We typically refer to our high-speed scopes (51xx series) as digitzers, in which case, there are no drivers for MAC. Our other DAQ cards, E-Series (60xx) and M-Series (62xx) work with DAQmx base according to the readme.

If you are using a DAQ card, I would like a bit more clarification about question 2. When you say start at the same sample point, do you mean start simultaneously so that the input and output start at the exact same point in time? If so, I may suggest triggering them both off of the same digital line.

[john.clements]

David,

Thanks for your reply. After posting the first message I realized it was too thin on detail - especially for question 2 - and so I posted a second message titled "Synchronize input and output tasks to start at the same sample point [C++ NI_DAQmx Base]". Perhaps you could take a look at that and get back to me.

I think you suggestion to trigger input and output streams "off of the same digital line" may be what I'm looking for, but where does the digital pulse come from? I don't want to set up an external pulse generator - I want to do this all in software.

John.

[David L.]

John,

If you would like to start them simultaneously, you will need a single digital value change (high or low), as you can set the digital trigger to look for a rising or falling edge. DAQmx base does not support software triggering. (Found in the DAQmx Base C Reference Help). Also, in order to keep this issue as one forum, let’s continue in your other forum here.