I haven't tried to bit bang SPI on the cRIO, but it does seem like it would difficult in Java. In college I did it on a microcontroller, and it wasn't too bad with easy access to interrupts.
I've been playing with the SPI library posted here:
http://www.chiefdelphi.com/forums/sh...ad.php?t=99803 It might be easier to use that, and bit bang an SPI slave on the Raspberry Pi.