[FPGA] - NI 9401 - Digital Input Read Issues?

[AllanIL]

I am having some issues with the NI 9401 Digital Input, which is having a consistant reading. I have a photogate that is powered off a digital output and is fed back into the module at a digital input, however I am unable to read the input multiple times. My LED blinks once and will never blink again until I restart my CRIO or recompile. I have initiated the input and output ports, turned them on, and loop continously for a reading. Any idea what is going on?

[GerdW · Accepted solution]

Hi Allan,

why do you "turn on" an input channel?

Writing a value to a DIO pin is usually done for outputs!

What is connected to your DIO pin 5? Did you check the input with a DMM measurement?

How long are the pulses measured with this input? Do you really think you can see short pulses by blinking an LED indicator?

[AllanIL]

Hi GerdW,

I my photogate input is attached to DIO pin 5 and my DIO input for my photogate is at DIO 0. The input for the DMM measurement has not been checked yet neither with the pulse widths, however I had it working before by setting the input on as the LED should hold HIGH when something is blocking the photogate. I am unsure of what is exactly going on here and will try to measure the pulses, but I am unsure if I will be able to do. This would only be possible if I can get the equipment.