I can't seem to set a trigger for my NI-9221 modules in the cDAQ-9188 chassis. Searching the forum I believe it's the case that in fact this module is incapable of using it's AI channels as triggers. Is that correct? Assuming such, I attempted to use the PFI0 port as a trigger, but I cannot get it to work either. Is this even possible? If so, could someone give me some tips on how to get this working. Thanks!
I'm afraid you're right, you can't use any of its AI Channel as triggers and there is no PFI lines on the NI-9221 module.
However, to start your acquisition, you can use the BNC PFI lines of your chassis, but you'll only be able to use a digital start trigger, not an analog one (see this helpfile of cDAQ-9188 chassis).
If it's OK for you to use a digital start, could you tell me which Application Development Environment are you using ?
So I suggest you to try this example.
For the clock source you can use either "OnboardClock" or an external clock plugged to one of the chassis PFI.
For Trigger Source select the chassis PFI on which you plugged the digital signal which will trig the acquisition.
Hope it will helps !