Sequential Digital Outputs or Counters

[LCY]

I am trying to sequentially flash four digital outputs.  I want to run them at a frequency, with 25% duty cycle, one after the other.  To be clear, output one on for 25%, output two for 25-50%, output three for 50-75%, output four 75-100%, then repeat.  I tried using four counters, but they are not synchronized, so the pulses do not stay sequential.  I am using a USB-6143.  This seems really basic, but I am a pretty new user.

Thank you - 

[MCOTO]

Hi,

You can use the output of one counter as the trigger for the task of the next counter. If you don’t know how to route the signal internally take a look to the next link.

https://www.ni.com/docs/en-US/bundle/ni-daqmx/page/internalchannels.html

Also, your tasks must be configured as retriggable, except the first.

[John_P1]

Assuming you are using the USB-6343 (there is no USB-6143, although there is a PCI variant), you can either run 4 counter output tasks with triggering and appropriate initial delays, or you can use a single digital output task with the appropriate waveform--for example, using lines 0:3 you could generate {1, 2, 4, 8, 1, 2, 4, 8 ...} to get the desired waveform.  The frequency of each output would be 1/4 of your sample rate (the sample rate is configurable).

Either method would work, but using digital output seems like a much more straightforward way to go about generating your signals.

Best Regards,