B,
Welcome to the Cayenne community!
I don’t believe the PiFace is supported, yet. The latest note I could find is from a month ago-
http://community.mydevices.com/t/piface-digital-not-supported-yet/72/5?u=ian
I’m sure @bestes will jump in here and give us an update on the progress of the PiFace support, I’m in a similar situation with SenseHat.
Again, welcome,
Ian