Eventual debugging LEDs aren't part of the CPU, but part of the
electronics. Accordingly, define it in config.*.h, not in
arduino_*.h (which would be better named something like
"atmega_*.h).
The atmega32u4 timer 4 registers differ from other AVRs, requiring
changes in heater.c and mendel.c The teensy/atmega32u4 uses LUFA USB,
but does not have 'usb' in the name, requiring changes in the
makefile PID values read from a blank EEPROM are set to default
rather than using zeros.
Markus Hitter
David Forrest