I'm trying to hook up a TI-84 + (i have both SE/and reg) to a Raspberry Pi Pico W to integrate Wi-Fi to the calculator. I've tried for the past week on just simple I/O, but nothing. I've even purchased an ESP32 to be able to use the ArTICL library, but that doesn't seem to work either, as I've used the simpleIO example it comes with, to no avail. ☹️

I stripped a 2.5mm jack and attached them to the appropriate GPIO pins, with a 3.3v connection via a 10k resistor to keep the line high when idle. I'm not sure whether this is a code issue, or my hardware is just incorrect.

Can anyone with experience with mods like these point me towards a solution? A small script would be greatly appreciated too, as I've ran out of options and ideas.

What are you planning to create with this project?

Following up from conversation in #cemetech: there is no issue with using 3.3V I/O wtih ArTICL. I've successfully used this with a Particle Photon board at 3.3V I/O and TI-89.

If connected properly to the calculator, tip and ring should idle at the I/O voltage (3.3V) due to pull-up resistors on both ends and the way the link protocol works. You can can find details about the protocol on Merthsoft Hardware Link Protocol. So just plugging your cable into the calculator, should measure ≈3.3V from tip to shield and ring to shield.

Double check that the cable has continuity end-to-end and that no two pins are shorted. Then verify that after plugging in the cable, you are seeing the 3.3V on each pin as above. Then progress to setting your microcontroller pins as input with open drain or open collector and wire it in and confirm the pins still idle high.


Can you please share a picture or schematic diagram clearly detailing this setup to confirm wiring?

If you're still using the RPi Pico, you should be able to take advantage of its PIO module to help accelerate* I/O and maybe make it easier to do. To help you with that, you can take a look at my take on geekboy1011's project. It won't help you with the WiFi, but it could give you an idea as to how to get the I/O to work.

* At speeds this low, you really shouldn't need hardware(-ish) acceleration, but there's something to be said about not needing to worry too much about the details behind sending and receiving bytes.

Got and photos of your setup? Schematic, or wiring diagram?
the 84+SE essentially uses i2c with a different framing. So we do need to make sure things are translated right between the picos 3v3 logic and the calculators 5v properly.

Yeah, I left out some important details when initially writing this post, but I'm confused. What voltage does the Ti-84 plus I/O operate at? I'm getting contradicting answers. I'll get a picture uploaded once I get my mosfets in the mail. I'm considering using an ESP32 (3.3v tolerant) & ArTICL, I think it'd be better, but regardless I do just want to get hardware working for now.

If memory serves the Calcs pass battery voltage to the pins. So 3-6vs depending on state of charge.