Is there a VI in DAQmx that has the same function of "Down Counter" in Traditional DAQ?

[robbieyang]

Or how to realize this function using DAQmx?

Thanks very much!

Best Regards!

[MarkBlack]

This functionality can be implemented using the DAQmx Create Channel.vi. In the polymorphic selector portion of the VI select Counter Input >> Count Edges. On the top edge of the VI the middle node controls the count dirrection.

More detailed information can be found in the LabVIEW help at VI and Function Reference » Measurement I/O VIs and Functions » DAQmx - Data Acquisition VIs and Functions » DAQmx Create Virtual Channel

[robbieyang]

Thanks, Mark.
I noticed that.
What I want to do is to realize the capability of "DownCounterTest" based on traditional DAQ using DAQmx.
A source signal is connected to the "Counter Source0" pin; a control signal is connected to "Counter Gate0". Then, after running "DownCounterTest", I can get a new signal from "Counter Out 0".

I can do it using this VI and an E series card. Now I want to write a new program based on DAQmx and a M series card. I tried "DAQmx create channels" (attached as "DownCount") but it seems no output generated and I can't set the "gate mode" like in "DownCounter".

Could you help me check this?

Yi

[MarkBlack]

Yi

I apologize for misunderstanding your original question.

There is not dirrect equivalent to the Down Counter in DAQmx. Instead you can use the DAQmx Create Channel.vi to output any frequency pulse of your choosing. This can be accessed through the polymorphic selector portion of the DAQmx Create Channel.vi by selecting Counter Output » Pulse Generation » Frequency

[robbieyang]

Actually I want to generate pulses which can be controlled by Counter gate instead of regular pulses. In other words, when the gate is high the counter outputs pulses every N cycles of "counter source"; when the gate is low the counter outputs nothing. Do you have some methods? Thanks!

Yi

[MarkBlack]

Please look at the shipping example Gen Dig Pulse Train-Finite-Retriggerable.vi. This example can be found in the NI Example Finder under Hardware Input and Output » DAQmx » Generating Digital Pulses » Gen Dig Pulse Train-Finite-Retriggerable.vi.

This example allows you to configure two counters with Trigger Source gating the Counter as described in the VI.