Changelog from v4.0:
- Use 0805 SMD parts (instead of 1206).
- Add more parts to bottom side to make.
- Use ceramic capacitors instead of tantal capacitors.
- Add descriptive silkscreen texts.
- Make courners more round.
- Use SMD crystal.
- Add programming connector descriptions.
- Add test pads for MOSI & MISO.
- Add RS485 ESD protection.