If anybody else is playing with the TMC22# IC's and an Arduino I've found what looks like a useful library at
http://translate.google.com.au/trans...%26prmd%3Divns
The code comments, the PI doco etc are in German and I need to do some translation work to understand it better. Once I get some of taht to a usable format I'll try and post some relevant material.
I've not tested any of that code yet, my own attempts to communicate with the chip have been less than inspiring but a skim of the functions and procedures looks promising.
Bob