NI9401 unable to read digital pulses generated by encoder in FPGA programming mode

[AshwiniWini]

Hi all,

I am stuck and definitely use your help.

I am using NI 9401 on cRIO-9049 to read digital pulses generated by differential encoder. As 9401 is single ended TTL, I have connected only A and B signals (A- and B- are open). I am going to relace this module by NI9411 later. But for now, I have get this working.

I want to read pulses on FPGA using FPGA IO Node. I have connected encoder pin A and B to module's pin DIO5 and DIO6. This is how my chassis look like:

When I run FPGA  vi, I can't read any data from these encoder pins. But if I go to NI MAX and run test panel by changing programming mode to 'Real Time DAQmx' while FPGA VI still running, I can see FPGA VI gets the pulses from encoder. 

Can someone please help me to figure out what might be the reason for this behavior?

Thank you in advance.

Ashwini A Pandit

[ZYOng]

Try setting the line direction using FPGA IO Method instead?

How Can I Programmatically Set Line Direction to Output with NI-9401 in LabVIEW FPGA?

[AshwiniWini]

Thank you ZYOng for the response.

I can't see FPGA IO method, looks like it is not supported for my target cRIO 9049.

[AshwiniWini]

Hi,

I was able to set the line direction using FPGA IO Method on FPGA vi (previously I was trying insert FPGA I/O method node in real time vi).

But still having the same issue.

[AshwiniWini · Accepted solution]

Hi everyone,

I just realized a mistake: someone used my setup and disconnected the encoder pins from the cRIO 🤦‍♂️.

When I was using the Test Panel in NI MAX, it was simulating data, which I misunderstood as real data.

Lesson learned: Always double-check your hardware connections, especially when sharing your setup with others. I learned this the hard way.

Thanks for all your support.