AVR and HD44780 powered from 5v
Reset, SCL, MISO and MOSI are kept free for in-system programming
PB0-3 Are connected to DB4-7 for LCD data
RXD/TXD are connected to the Bifferboard (TXD operated in pull-down mode to be compatible with Bifferboard input).
PD4 --> E
PD5 --> RS
R/W permanently pulled low on HD44780