Hello. I wanted to see if anyone has ever tried or know of anything about sending data to a TI-83P with a 2.5mm-3.5mm cable connected to a headphone jack. It seems like it could be possible, but with extensive research I only seem to have found people attempting to connect it to an Arduino, not a PC. Does anyone have an idea on if this is even possible?

Is this what you're looking for? https://www.cemetech.net/projects/item.php?id=14

Not exactly. I mean a way to transfer data (like programs) between a computer and the calculator with the PC's headphone jack.

I guess technically it could be possible, but I don't see why you would want to do that. If you are unaware, there is a link cable made to connect your graphing calculator's 2.5mm I/O jack to a usb port

And there is a serial version for some older models like the ti-82.

These are already simple and easy to use.
Here is a tutorial on how to use these, on a very modern looking webpage

Never really tried this, but I'd assume you'd need to essentially build a modem between the two systems. TI-83+ has direct control over the TRS jack. To my knowledge, you can't straight up do this on a PC, as it's optimized for audio, so you'd need to send/receive data as audio, meaning you'd need to design modem software on both the PC and the TI-83+'s end. I wouldn't imagine it'd be very fast on the TI-83+'s end, you don't have anything like a sound card so you'd need to simulate that from scratch.

Given the TI-83+ has direct control over the TRS jack, it's quite easy just to buy a 2.5mm connector and then use that to connect the tip, ring, and ground to I/O pins of an Arduino, Raspberry Pi, or even the TI-Innovator Hub, and you can transfer data the quickest that way. That's why most people do it that way, it's fast, quick, and easy.

I'm not exactly an expert on this stuff, never tried building a modem before, but my assumption is it'd theoretically be possible but probably be pretty inefficient.

I was wondering the same, Has there been an update because i am not spending $20 for a cable.
I have a 2.5mm to 3.5mm but thats it

This is an old thread, but I think I can put it to bed.

The link protocol is based around an open-drain bus, where whether you send a 1 or 0 depends on which of the two lines you pull low. The receiving device acknowledges by pulling the other line low.

This means that any device participating in a transfer must be able to read and write both lines- you'd need a cable that you can connect to both a headphone output and a mic input. But wait, that's not sufficient either! Because you need to leave the line you're not manipulating floating so the receiver can acknowledge, a typical audio output cannot work: it will always be driving both lines and will not allow you to selectively drive one of them.

In short, no this is not possible.