This is the first in a series of Instructables that document the process of converting a vintage computer (in this case, a TI-99/4A) into a RaspberryPi workstation. You should know that the only thing we're preserving about the old computer is its physical form. We will not be using any original hardware or software, with the exception of the awesome keyboard.
Part 1 will show you how to convert the TI's passive keyboard matrix to a USB keyboard. We will be re-installing it into the TI-99 body, but once it's been programmed, it can be used for anything.
NOTE: this process can be used to convert any push-button matrix into a USB keyboard input device.
Thanks and Salutes:
Ido Gendel for his advice on how the code should be structured.
Sean McIntyre for his help with debugging the code.
Code for the Teensy can be found here: https://github.com/matthewepler/raspTI_keyboard
Supplies:Teensy++ 2.0 microcontroller
Micro USB cable
Bread board and standard gauge wire
30x female headers
55x male headers
ribbon cable (regular wire will do but this will make your project less of a wire nest. you need at least 7 wires in the ribbon)
10x 10K resistors
Wire cutters and stripper
Solder and Iron
4x small zip ties
TI-99/4A or any vintage computer keyboard with wired output similar to the one shown here.
If you have questions, feel free to contact me via the address on my site: http://mepler.com