Unfortunately it is still underdeveloped. There are two routes into SPI, a legacy mode and a demo mode. Neither are ideal.
I made a few starts towards a simple “will work okay” binary interface. Every thread evolves into a discussion of protocol buffers, which sounds super nice but is something I have yet to wrap my head around and nobody has contributed a prototype or pattern to follow.
The binmode test framework is a set of functions to control most aspects of the Bus Pirate. It is intended to be wrapped in any protocol someone wants.
Barring a hero contributor, I will put together something simple that nobody will like by the end of the year 