I needed to program my TI-83 for math class while I was attending college. Texas Instruments was nice enough to provide a “transfer cable” for 2 calculators but they wanted $20 for one that interfaced with the computer. I cut their cable in half and built 2 “programmer cables” with just a few resistors, transistors, and some hot-glue.
Too cheap to buy a cable so I hacked my own together with spare parts.
My TI-83 Homebrew cable. I cut the provided transfer cable in half to make 2 cables to load software from my computer.
some resistors, a transistor and more hot-glue