I'm having trouble getting low level help with the TWI interface. So I think I'll have to use the wire library.
Good idea. I havn't seen any complaints about the the Wire-lib around here. so it seems to be working fine for most people.
I never got far enough on my own to implement an ISR.
I don't think you could write a library for the TWI without using Interrupts. (the Wire-sources provide a good example how to do this :-) )
Sorry, I did not go through your code maybe someone else will do that...