Hi guys,

I had posted a comment regarding a TI-81 ViewScreen and my nefarious plans for it over on Reddit r/calculators. I was encouraged to post here with what I found and what my setup looked like.


So for clarity, I'm interested in being able to read the data going to the screen of a TI-81. My method was to take a TI-81 ViewScreen pair, cut the ViewScreen off, butcher the TI-81, and solder in flying leads to go to my logic analyzer. And then let the logic analyzer collect enough data to decode the signals and follow up with a bit of custom hardware to remove the logic analyzer from the equation.

So I made three videos and put them up on YouTube.

The two shorts show the hardware, while this video shows the output from the logic analyzer: https://www.youtube.com/watch?v=aAIXVZRyF6Y

The hardware mod (short): https://www.youtube.com/shorts/i6PTvPNpElI

And what's inside the ViewScreen (short): https://www.youtube.com/shorts/ccAoEfTHOoo


Let me know if you have any questions.


Thanks,

John

Hey very cool, I love the 81 - what is your goal once you have the display data read?

Any more vids or learnings?

There is a way of dumping the TI-81 ROM using three programs that will crash the calculator and dump the ROM to the LCD. And there have been folks who would video the screen as the ROM was passing by, and by using OCR, re-created the contents of the ROM.

My approach could be used to bypass the video/OCR part of the process. Ideally the logic analyzer would be replaced by a Pi that would create the hex code on the fly once we figure out what signals do what. Think of it as a "Video Modem".

I posted the process here because twisted_nematic57 over at Reddit asked me to. It ties into something that they are interested in doing.

And it all started out as a suggestion that I made to Tiny as a possibly easier way of getting the dump.

Feel free to make suggestions or just ask if you need better pictures of the process. I have export data from the LA that I can share, but the files can be substantial in size.

And yes, there is another video:




Thanks,

John