TI-92 Serial terminal Hack

Hi, today let's talk about one of my 'in-progress' work : TI-92 as serial terminal Hack.

I've bought a broken TI-92 version 1 some weeks ago..., I wanted to hack only keyboard & screen, but as it was too difficult for my skills, I deciced to repair/reborn it & reprogram it as a serial term. (for my RPI zero W for example ;) ).

Let's see how did it look.....

I started to disassemble mother board & clean it with white vinegar...

I checked for the batteries crossing line, found the +5vcc & choosed a GND from anywhere on the motherboard, then soldered a micro-usb plug to POWER it again

I continued my old-dead-code-work to drive a TI-8x/9x with an Arduino (that was not my 1st attempt) & was able to produce something working....

And .. here's a screenshot of the TI-92 !

The problem with the 1st version of TI92 is that it doesn't run native ASM programs, so I had to dump my ROM, add 'FARGO' patch on it in order to code my Serial Terminal.

Then is was done, I had to make my Arduino capable of (re)sending a backup (.92b) to the TI, then copy flib.92p & shell.92p to it (that took me a while - more complicated than requesting a simple screenshot ... for sure).

Now I can write my Terminal program with a FARGO-PATCHED version of GCC4TI, then I upload it directly with my arduino (just a sub-routine in the terminal code), I changed from Arduino UNO to Arduino ProMini 5v (same specs as UNO).

If as me, You plans to communicate with a raspberry, don't forget that Arduino UNO/ProMini5v are 5v logic signals BUT the rapsberry is ONLY 3.3v proof !!!!!

So don't forget to protect it's RX line as on the diagram below....

The (early-stage) code for Arduino & TI92 can be found here (GitHub)

It's very ugly @this time, I'll try to make it better as possible

details also available on Hackaday.io 

See you soon !