I've seen a few USB C mods for the TI-84 Plus CE but they all seem to have the same issue: they're charge only. This mod replaced the USB port. This mod simply added a secondary port.

Even if the mods above could get data transfer working, as I understand it, the breakout boards would only support either transmitting data or receiving data; OTG functionality would be lost.

I'd like to keep OTG functionality so I went on Amazon and searched for OTG adapters I could take apart. It took a bit of digging but I found this adapter which claims to retain OTG functionality! I noticed there's a catch though:
Quote:
This Adapter only supports charging from wall charger or car charger, It will start OTG function once connecting computer or other devices. OTG function and charging function could not be used at the same time.

For those that understand USB better than I do, is the ideal USB C conversion mod (charging + OTG at the same time) possible? I'd like to get a clear understanding of why this may or may not work before I hack my calculator apart again.
I'd have to look into it in more detail, but what you're looking for is referred to as a DRD and a DRP in the specifications, for dual-role data (either UFP or DFP) and dual-role power (either source or sink) functionality.

Operating as a USB-C sink is relatively easy, because you only need to present appropriate pulldowns on the CC lines. Operating as a source (if you want to use a self-powered device) requires detecting a sink's pulldown and turning on VBUS, which requires at least a little bit of smarts. Operating as a DRD requires the ability to switch between CC pullup or pulldown, but is otherwise no more difficult than being a DRP.

TI's SLYY109 application note provides a pretty good introduction to the basic system requirements for assorted USB-C modes, where the relevant topology for your question is "USB Type-C DRP/DRD USB 2.0 without USB PD."
Thank you for all the resources Tari! It'll still be a little while before I can work on this project fully but I have a lot of motivation to do it now. I noticed today that the USB port on my calculator broke! The plastic piece that keeps the pins in place is missing now. Sad

Here's my blue CE's port compared to my working, red Nspire's port.

Edit: TLM 1800th post!
This sounds like a great idea, and it certainly would be great to see the USB hardware updated a bit. Pardon my dumb question, but would the mod affect transfer speed at all (assuming you're able to still transfer files)?

I know that the Zero Calculator is supposed to have USB C, which I think might be the first calculator to intentionally have it? It'd be interested to see how your modded version compares to the Zero Calculator when it's released.
TIny_Hacker wrote:
This sounds like a great idea, and it certainly would be great to see the USB hardware updated a bit. Pardon my dumb question, but would the mod affect transfer speed at all (assuming you're able to still transfer files)?

I know that the Zero Calculator is supposed to have USB C, which I think might be the first calculator to intentionally have it? It'd be interested to see how your modded version compares to the Zero Calculator when it's released.

It would not affect transfer speed at all.

Yes, a few calcs (numworks/HP prime) use micro-usb but I'm pretty sure Zero is the only one using USB-C currently.
yea it wouldn't affect speed, but its still better in every other way
OK most of the circuitry details go over my head so I sought help from my electrical engineer friend, who ended up getting more confused than me because USB is a mess 0x5. Anyways, my friend figures that in order to get the rp/rd switch required for DRP, I would need an IC like the TUSB320 and configure it like Figure 8-7. I really would like to avoid adding in ICs so this project doesn't get too complex.

I started looking for other solutions and stumbled upon this Russian site (google translated) that showed pin to pin connections for a variety of different adapters. The closest I found to my application was a female micro usb to male usb c.

Click for full size

There's a few issues with it. First, I don't know if simply replacing the male connector with female connector is something I can do and still have everything work. Second, it doesn't seem to really follow the documents Tari provided so I'm skeptical it'll work the way I need.

Before I proceed, I'd like to understand if this project is feasible without an IC. If an IC is required then that'll add another learning curve and slow this project down a lot. If an IC isn't required, is the pin to pin photo I posted a viable solution? There's quite a few options on the website I linked, perhaps there's a different solution there?
  
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