First revision of the board works mechanically.  Board bring up progress so far includes the power subsystem, boot loader flashing to microcontrollers.

 Wanted to keep as much of the TI-92 case and features as possible.  The new board should run from primary (alkaline) cells or via USB-C power connector.   The buck-boost regulator will run on anything you can pour in the tank (a wide range of voltages). 

It would be great to implement charging, automatic switching from USBC to battery and back.  I started down this rabbit hole and decided to save this for a future rev.  There are AA size lithium cells that could fit the case and provide power, but all this was too much for a first rev.

The USB hub and peripherals on the board will be connected to the Raspberry Pi via soldered jumper leads, likewise power.  This is more reliable and less bulky than using connectors.  There are extra USB ports brought out to test pads on the board that could be used to connect sound cards, external mice, etc.

The extra ATMEGA was intended for data collection, with the unused pins available for extra peripherals inside the case.  You'll see some protection circuitry on the input pins -- this means these pins are mostly for use as inputs. 

Love to hear your thoughts and comments.  Definitely a work in process that could use a small group of amazing people to come to life.