I got my shiny new ATmega328p from the Nerdkits guys today, and the drop-in replacement following the nano guide worked really well. The only change I made was to copy the info from their io_328p.h and paste it into the bottom (above the final #endif) of the c:WinAVR-20090313avrincludeavriom328p.h.

By doing this, I don't have to modify my code to include the 328p stuff, I can just change the make files and switch my builds between the two different devices.

Another thing I had to do was rename my signal handlers away from the "SIGNAL_XYZ" form to the "XYZ_vect" form. This isn't a big deal because using the _vect format will work for either chips -- but for some reason the more-spelled-out versions aren't included for the 328p.

Overall the upgrade was pretty seamless and the instructions provided by the Nerds worked really well. Now I can get back to my software-UART writing project. I've got transmission working PERFECTLY -- It's interesting trying to debug timing events on a device where injecting debug can cause timing shifts.

This is a great library mod, I've been looking for something like this for a while now ever since I received my ATmega328p from sparkfun.