[yash101]

If you are using a co-processor, you are already thinking out of the box. You will also need to think out of the box to devise a method of communicating, Pi<=>cRIO. I think you might find i2C quite easy and since it is hardwired to the cRIO, it will be high-speed, minimal lag. Also, the lag that will be present can actually by thought about before and can be compensated for in the code!