The TI-Pi – A Raspberry Pi powered TI-99/4A


Anyone remember the TI-99/4A? We do. Well not anecdotally, but out of our fondness for retro computing.

The TI-99/4A was one of the first home computers (in fact its immediate predecessor, the TI-99/4 was the first 16-bit personal computer), released in 1981. In the style of its later (but more popular) cousin, the Commodore 64, it was self-contained in a single console along with a built-in keyboard. What made the TI-99/4 series extra special was its peripheral expansion system, a collection of different modules that could be stacked to expand the system’s capabilities. As you can see, this could get out of hand pretty quickly…



The TI99/4 with expansion modules.

We decided to resurrect one of these bad boys and make a retro-inspired emulation machine — Raspberry Pi style. To run the system, we used the RetroPie Project. This Raspbian-based distro is a fairly comprehensive emulator environment. It’s relatively easy to setup and quite robust.

One of the main things we wanted to do in this build was to retain the utility of the original built-in keyboard. We used Matthew Epler’s method of doing this. He used a Teensy++ 2.0 microcontroller and wrote some great code for that. We wanted to save a few bucks, so we used the standard Teensy 2.0 and modified his code a little to match the pin outs.

We wanted something more permanent, so we took the breadboarding into Fritzing, an amazing piece of software which made the PCB design so much easier.

When it came to PCB etching, we decided to follow the steps laid out by MAKE’s very own Collin Cunningham. Once we got over our own “duh” moments, it turned out to be a great success!

The rest of the build was pretty straightforward — a lesson in organizing cables and using a hot glue gun without self-injury. However, we decided to step up the game just a bit and use an original speech synthesizer module as a housing for our SD card slot (an extension from the SD slot on the Pi so that it would be possible to easily switch out the distro without having to open up the case).

Take a look at our video below to see these steps in action along with the rest of our build!

YouTube player



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Shannon Woodruff

Shannon is a chemist by training, who loves to make things in his free time. In 2014, he and his friend, Brian J. Gardner, formed The Circuit Surfers, in order to showcase projects that they have attempted in order to enhance their technical skills and to have a little fun. They are based in Dallas, TX and you can find out more about them and their newest projects at The Circuit Surfers

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