I am working on a WiFi-capable TI-84 using the Adafruit QT Py ESP32-C3 WiFi Dev Board, ArTICL, and PHP-based data pre-processing (the PHP scripts will run on an external server and do the work of getting information the calculator/ESP32 can deal with.)

What I have done:
Track down a way of getting the ESP32 to communicate with the TI-84 - ArTICL
Find a WiFi-capable microcontroller that should be able to fit in the TI-84's case with minimal to no modifications and run on the TI-84's 6-volt battery pack - Adafruit QT Py ESP32-C3 WiFi Dev Board

What I still need to do:
Get a TI-84 with an IO port (just waiting for my local thrift shop to be open again)
Write the necessary code (should be pretty simple, especially for the first proof of concept)
Connect the TI-84 to the ESP32
Test
Discover that I made a bunch of mistakes in the code I wrote and spend hours finding the bugs (my favorite part, obviously)

This sounds really interesting and like a great project! I'm excited to see how it turns out, be sure keep us updated

ESP8266 or ESP32 are a good choice, calc can power them and they have lots of options.

Are you planning on tying them to the internal IO port pins?

[quote="tr1p1ea"]Are you planning on tying them to the internal IO port pins?[/quote]

Yes. Hopefully that way it will look like a normal calculator.

The D-bus (I/O port) soldering pads may still be present in calculators without the port, so you may be able to solder directly to that. If the pads have been removed, the pins on the chip itself are almost certainly still present, but soldering directly to the chip requires very good skills and a good iron.

The pads are still there but the entire circuit was removed, not just the jack itself.