Input from physical buttons triggering events in program

[k_paton]

Hi,

I'm trying to use the input from digital signals generated by a physical button to trigger events/functions in the code I'm working on. I'm building a unit that will have buttons that will send input via the digital I/O lines of an SCB-68. I can read in the values of the lines, but I don't know how to have (for example) the line going high trigger an event in the program. Would it be best to have functions reading the lines running in different threads? I found an example in the CVI 8.5 help dealing with change detection events but wasn't able to make sense of it.

Thanks!

[crossrulz]

Which language are you using?  In LabVIEW, I would tell you to use a shift register to hold the previous value and look for a change in state.  On the change, I would use a queue or user event to trigger an action.

[k_paton]

Using C and LabWindows. 

[niNickC]

Hello,

If you want to avoid polling, you will need to use the change detection event:

http://digital.ni.com/public.nsf/allkb/DF5719473800838086256F1E0054FD7B

I would image you would read a port at a time then in your event call back, see which bit has changed and call the appropriate function.

Maybe if you had some specific questions about the example I could help you further?

Otherwise, you would need a separate thread, reading the digital values and checking for a change. If a change occurs then call your function.

There should be plenty of DAQmx examples to help with reading digital data.

I hope this helps.