If you still have a drawer full of slap bracelets from the 1990s because, you know, they might come back, then you’ll appreciate [Vorticon’s] latest project. Sure, we see lots of weather stations, but this one is controlled by a TI 99/4A computer. This home computer from the 1980s was actually ahead of its time with a 16-bit processor.
The sensors use Xbee modules and an Arduino Uno. Of course, the Uno has more power than the TI computer, but that’s not really the point, right? He’s made a series of videos detailing the construction (you can see the first one below, but there are five, so far).
Normally, talking serial to the Arduino would require assembly language on the TI computer. However, TI hacker [Rich Gilbertson] already fixed that. He created Rich Extended BASIC (RxB), which has a CALL IO statement that was perfect for [Vorticon’s] needs.
The TMS9900 CPU had a novel feature where subroutine calls caused the registers to shift so that each subroutine had some registers in common with their caller and some that were private. This sounds good on paper, but the registers residing in main memory was a death sentence as processor speeds increased (the 9900 in this computer only ran at 3 MHz). It also had a sprite-based graphics processor that was used to good effect in games.
No matter how impractical, we love these old retro projects. Even though a new owner of a TI 99/4A back in the 1980s would have been shocked at how much computing power you can buy for the cost of a good meal now, the TI was still capable of some impressive output for its day. While it might not be able to play Doom or Call of Duty, it can handle Flappy Bird.