I am trying to use the AI Start TRG input on my PXI system and am having problems. I have a PXI-6133 card with the TB-2709 SMB terminal connectors. I used this exact setup a few years back with a TTL pulse going into this AI START TRIG pin to trigger data capture. Now this same VI and hardware is not working. When I started diagnosing this, I determined that my AI START TRIG pin is putting out 5V. I am guessing this pin got switched to an output somewhere along the way, but I cannot find any way to set it back as an input. Has anyone seen this problem before, or know how to fix it? Thanks!
I am measuring the 5V output with a multimeter.
After digging some more through manuals I have found that this pin is supposed to be connected with a "weak" pullup. It is pulling 5mA of current when I ground this output, so it sounds like the pullup is 1k.
I usually think of a weak pullup as more like 10k, so my external circuit to create the trigger pulse was not working. Now that I have adjusted the resistor values in my external circuit the trigger is working properly.
I am still curious how to use this pin as an output signal if I want to send out a trigger pulse. I cannot find any way to change this pin from an input/output in Labview or in NiMax. Can you provide any suggestions on that?
You could potentially create a clock output virtual channel in LabVIEW and use a property node to change the counter timebase source to that pin.
I haven't tested it out myself, but that could be something worth trying.