DevicePrint is not impossible to make work!!
Well at least with the arduino fourm.
This is what I got:
uFat / DevicePrint Demo
All initialised OK!
I did three things, first, in libraries I changed wconstants to WConstants as well as wprogram to WProgram. Second, I built sirmorris's circuit instead of some other thing. Third made sure there was a file on my SD card named data.txt and some data on it(I put 11mb of "B") on it. Thats it!!
Thanks sirmorris and everybody else!!!!
Does anybody know how to make it write over the 512 bytes?