Digital input and output with "1 Sample (On Demand)" issue

[Lysandros]

Hello Dear NI-users,

I am developing a labview interface for controlling a brushless dc motor. The motor drive needs a

--"enable" signal for the initialization: a digital high/low output and

--"command signal" for the position: a analog output

Both signals should be generated in real time in labview, via the "1-Single on demand" option with the DAQ-Assistant, running in a while-loop.

The problem is, that labview treats the signals to/from the "DAQ-Assistant" as arrays, therefore I need to generate an array with just one element, see picture.

Is there a more elegant solution to this?

[crossrulz]

Just use a single control and then Build Array reduced to 1 input.

[Christoph_D]

Hi,

I agree with crossrulz regarding the build array function, ...

... but if you want to do 'real-time' control you better have HW that supports Hardware-Timed Single Point Sampling.

Does My DAQ Device Support Hardware-Timed Single Point Sampling Mode? - National Instruments
http://digital.ni.com/public.nsf/allkb/B4E831774F29FB038625754C0081C050

Or at least do not use the DAQ Assistant since that probably initializes and deinitializes the DAQmx task every time, so probably use the lower-level DAQmx API functions as explained in the DAQmx examples.

Best regards,

Christoph

[Lysandros]

Thanks for the reply.

I resorted in using the traditional DAQmx blocks. This way I can write/read my data much more convenient without having to compose/decompose arrays 🙂