- Pin mapping (Digital, Analog, I2C, SPI) identical to Uno Wifi 2.
- Designed for "amateur" assembly. 0805 SMT component size.
- Use COTS modules for power, USB.
- Allow for partial builds.
- careful layout of analog paths.
- break out most unused pins. Somewhere.
- allow for UPDI debug connection. But maintain the SPIness of the ICSP connector (sigh.)
- use a serial bootloader for upload. Probably at the end of memory so that apps load at 0 (like old AVRs and Uno WiFi2), even though that's inconsistent with the "bootloader" features of the chip.
- Move Aref down next to the Analog pins.