adilinden:
My primary objective for the 1284P is to get the additional RAM (and code space). Also needed to maintain the traditional Arduino dimensions and header locations, including ICSP. There is more then enough IO on an ATmega328 for my purposes.
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So all considered, it is built with my particular specifications in mind.
It looks good, different from Bob's (Crossroad's) Bobuino and also my Calunium, so between us there are a range of options for using the ATmega1284. I hope that somehow we can all collaborate to get the Arduino software fixed so that the SD and other libraries don't make assumptions over pin mapping but use the proper pin-mapping mechanisms implemented in v1.0.
How did you estimate the area needed for the PCB heatsink?