i'd recommend to use the NI USB-8451. this device provides I2C and SPI. programming is very simple. it's really worth its price.
I am trying to develop my own digital communication protocol in LabVIEW, is basic SPI communication, I will be using a parallel port to talk to my device, has anyone done anything like it in LabVIEW, I believe I would need some DAQ built-in functions to acomplish this as well as some Port I/O libraries, does anyone know where I can download this from NI?