I am posting here, but this may need to be moved to ASM. I have an idea, but I am stuck on how to implement it.

I would like to use a ti83+, ti84+ or ti84+SE as an external screen for a computer, and I know I *probably* couldn't use a ti83 because the clock speed is too slow. Now, I'm not thinking of a terminal or plain text display, I'm thinking of sending b/w picture data over the link port, as to address each pixel on the screen. I would have an arduino hooked up to the tip, ring, and ground. The tip would be a clock, and at each half cycle of the clock, a but would be pushed over the ring. These bits would be stored in ram, building up a picture file, and then the picture would be called up ti the lcd. The calculator would let the arduino know that it is ready for the next frame, and the whole process repeats. Is this even feasible? Where would I begin?

Yes, this is entirely possible; you may want to take a look at Kerm's ArTICam project; of course, linking there is mostly done with basic commands. You would get more speed with an assembly program, but the main limitation is that transfers occur a bit at a time. This probably isn't too big of an issue for the monochrome calculators though.

As we were discussing on IRC, you'd want to do something to limit the number of screen updates, especially if you wanted more than 1 bit of color depth. At least on Linux, you can make your own framebuffer driver that would offer an fb device and allow the calculator to be used like any other monitor. Of course, actually writing the driver and the calculator-side software (and assuming that you had sufficient GPIO pins on your computer/Raspberry Pi/etc) would be rather challenging indeed. You started by mentioning a computer, and then you went on to discuss the Arduino. Did you mean to ask if you could use the calculator as an LCD for an Arduino? If so, you'd probably have to write a lot less code. On the other hand, the 768 bytes you'd need for a monochrome LCD buffer is almost 50% of the Arduino's RAM, so it would be an interesting challenge to implement this on the Arduino.

I was thinking more along the lines of using an arduino as a middle man between calc and computer (any computer at this point). The whole frame would not have to stored on the arduino, as the arduino sets the clock, so it could receive part of the picture from the computer and then send it to the calc.

edit: The idea could also spread as to use the calc as a grayscale sd card image viewer. Using the library Kerm has written for his gameboy camera thing, the calc could request 3 or 4 pics, and the arduino could send 3 or 4 differnet pics based on a single one read off of an sd card, converting it on the fly. The 3 or 4 pics could then be called to the lcd to create a grayscale pic.

edit: Looking deeper into the library for the arduino that Kerm wrote, the pic data could be lulled from anywhere; an sd card, the computer, a camera, another calc, random number gen, or an equation.

edit: I looked into linking protocols, and CLAP by Tim Franssen [http://clap.timendus.com/] seems to be promising as to how fast data can be transferred. This would allow each of the 768 bytes to be manipulated easily, as it truly is just pull a line low and go.

CLAP is similar to but (in my opinion) less well-developed than CALCnet, but since you're only communicating between a single pair of endpoints, there's no point in not using something like the TI-OS's link protocol as supported by ArTICL. Of course, it's up to you, but I think it's better to start with something that has been tested to be robust and functional (like ArTICL and the TI link protocol) before experimenting with something less proven.

Oh wow. I was trying to think up a new project to work on, and was googling around seeing if anyone has done a calculator-as-a-screen thing. Who know that my own 3.5 year old thread would be the 3rd Google result. Might as well finish what I've started, right?

Has anyone found a way to use the output from my PC and an input and use that on the ti 84 like a monitor? I've been DYING to do this for the longest time but don't know how to. I'm kinda new with this stuff

https://github.com/dnmalenke/Calc2KeyCE

And you can see it in action here: https://www.cemetech.net/forum/viewtopic.php?t=17714

That's really awesome, but I don't have a ce calculator:( I was wondering if this would work on a ti 84 plus because I think it'd be cool to play modern PC games using it and posting it on YouTube

...You have no options unless if you code yourself and are fine playing monochrome with a pretty bad resolution. Sorry.

Bah, I can't code to save my life. Thanks for the speedy response, and I might look into the ce option. I know of a program that allows me to put videos on the ti 84 and even has four levels of gray, but inputting in real time would take some work. I don't really have the time to make a program for it, if it's even possible, because I am nothing more than a wee little highschool boy. Maybe someday someone more dedicated than me will push the calculator to it's limits