Well I finally got my hardware in (a 9205 in a cDAQ USB chassis). I'm running DAQmx 19. My simple goal is for this little vi to wait until I get a falling edge through about -0.050 volts, than grab some samples on the same channel. I realized that I need to use a "Start Analog Edge" instead of "Reference" like I was before.
Now, THE PROBLEM - no matter what analog value I give DAQmx Trigger, it won't wait for more than a second or 2 before "falsely" triggering. For testing, I'm using a high quality HP variable power supply, and I've verified the differential voltage at input 0 with a good Fluke meter. I've also verified using NI-MAX Test Panels that the voltage at the card input is solid, and what I think it should be. I've given the DAQmx Trigger function all sorts of crazy trigger values, -10V, +10V, it doesn't matter - it always just waits a second or 2 or 3, then breezes on thru as if it had received a valid trigger.
I got the brilliant idea for how to terminate the vi when the app shuts down from DAQmx Trigger from Bert McMahan, BTW. I *think* it actually works.
So there might be a problem with creating 2 separate tasks that use the same input channel - I'll fix that tomorrow by jumpering the channel 0 input over to the channel 1 input. Could that be my problem maybe?