I am looking at some ways to generate differential digital outputs with the cRIO. I see that there is one solution which is the NI 9753 module. This module does leave something to be desired for my application as it is does not have the same ratings as far as temperature, vibrations as your standard NI modules.
Another option I was thinking of is this-- the NI 9871 RS-485 modules essentially puts out differential digital outputs so is there a way I can use FPGA mode to directly set the TX pins to high or low?
What is your overall application? What sort of data are you planning to output? Are temperature, vibration, etc. ratings a concern in your deployment?
If you already have LabVIEW FPGA and NI-Serial installed, I'd recommend going in LabVIEW to Help -> Find Examples and searching for "987x Serial Loopback." This will give you an idea of how to write individual bits to the 9871 card.