Jump to content
  • 0

usb 1808x : Synchronizing analog output and input using LabView

Francois Ouellette


Hello all,

I'm using the USB 1808x to generate a modulation signal to a laser (5 kHz square wave), and detecting a reflected signal from sensors, which are then analyzed. I need very good synchronization between the output and the input, because the measurement depends on the shape of the reflected signal. I'm now sampling both output and inputs at 200 kHz, but require synchronization to be better than, say, 100 ns between the two.

Right now, I use the LabView vi's to generate two tasks: one for output and one for input, as it seems I cannot generate a single task doing both. I've merged together the two examples VI's for continuous generation and continuous acquisition. The whole thing works well, except that there is always an arbitrary delay between the two that changes whenever I start the program, which is not just an integer number of samples, but can be a fraction too. It's really not clear (to me, anyway) what is the best way to synchronize the two. Should I use an external trigger or external clock? If so, how to use it within the available vi's? 

I will post details of my vi structure later if necessary.

Thanks for your help!

Link to comment
Share on other sites

2 answers to this question

Recommended Posts

  • 0

Hello @Francois Ouellette,

I recommend you set one task to external clocking and the other task to internal clocking.  Since input follows the output, I would set/start the input task with external clocking so that it waits for the output task to start first.

you will need to install a physical wire (not a virtual one  ) from the USB-1808X's OCLKO to ICLKI prior to running your vi, starting the output task then the input task.

If that does not resolve it for you, then please save a copy of your vi, and then strip out anything not required for me to see to the issue you are referring.



Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...