In upgrading the IC35 I see two main aspects to be addressed, processing and the display. To be useful I think it makes most sense to put in a Raspberry Pi Zero, since I don't want to spend a lot of time getting the Z80 to work and there's a bit of space in the case. I would like to reuse the display but am also considering putting in one of those ubiquitous 3.5" touch screen displays for higher resolution (and color).
In addition to the processing and screen the following will also need to be addressed:
- Keyboard; it's probably best to design a custom PCB for the keyboard in order to make efficient use of the space inside.
- Battery management; can possibly be integrated into the keyboard PCB
Other features I would like to implement are
- Put a SD card slot in place of a MMC slot
- Make use of the old serial port in some way
- Put in an IR transceiver where the old one was