Another TI-92 Raspberry PI PCB Upgrade

This project is for anyone who loved building a Gameboy Zero. Put a Raspberry Pi in your TI-92, and do data collection and science stuff

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We are creating a circuit board (and firmware) to replace the standard TI-92 circuit board perfectly. The new circuit board includes a USB hub and two ATMEL microcontrollers. One ATMEL controls the keyboard and enumerates as a USB HID. The other is compatible with the Arduino development environment and allows for data collection. There are free USB ports and tons of available space for other DIY add-ons. Imagine of all the geekery just waiting to be unleashed.

I've tried for several months to join the other TI-92 pcb project here on with no success. Finally, starting a new project seems like the right thing. The board was designed in Altium 'cause day job. Anyone interested in porting the project to KiCAD or similar? Board bring-up is in process. Could use help debugging the USB hub, ATMEL firmware, etc. I have boot loader running on the microcontrollers -- need to add test pads for this. I have spare boards. Not too hard to assemble one yourself (skillet reflow or hot air rework station) If you can demonstrate you are serious about the project -- maybe by finding a schematic error or such, I'd love to send you a board. Love to have the help. Some modification to the TI-92 housing is necessary to fit the (slightly) larger display. I'll post more pictures. If this seems like fun to you, let me know?


Schematic PDF for the October 17th 2022 design revision

Adobe Portable Document Format - 2.31 MB - 03/09/2023 at 01:30


Gerber files for the October 27th design revision

Zip Archive - 143.43 kB - 03/09/2023 at 01:29


  • 1 × Raspberry Pi Zero W
  • 1 × Pimoroni HyperPixel 4.0
  • 1 × TI-91 Donor
  • 1 × This PCB

  • Hello!

    Jamie Nichol03/09/2023 at 01:50 0 comments

    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.

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Jamie Nichol wrote 03/09/2023 at 01:41 point

Looking for a few good techies to help get this over the finish line.

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