The TI-84 KE (Keyboard Edition), a keypad and case mod of the CE, turning it into a desktop calculator.

The KE is a custom mechanical keyboard built around the CE motherboard and screen, replacing the keypad with an array of Cherry-style keyboard switches, and custom keycaps to boot!

Current Completed Project, kits being made now!



Current Design Render: Flat, Acrylic plate, snap-in screen bezel, PCB placement



Old Design Render: Flat with angled feet, cheap to produce, can fit in your backpack:



Oldest Design Render: Curved DSA Profile, looks great, but super hard to build, not portable:



Here is the to-do list, and current progress (- Incomplete, + In Progress, # Completed)
# Decide on the key layout
# Determine the keycap colorway
# Design the keycap legends
# Order keycaps
# Order dye-sublimation printouts
# Buy a new rev. M+ CE for the project
# Reverse-engineer the keypad matrix on the CE
# Determine test-point soldering locations for keypad and battery
# Design the PCB
# Order the PCB from JLCPCB
# Test the fabricated PCB
# Design the case
# Design the switch plate
# Test-fit the components in the case
# Choose key switches (Hako Violet) (Just for me, not for the other 4 to be shipped)
# Order switches
# Assemble one complete TI-84 KE
# Run a battery life test with LED's on
# Test every key works, and everything functions
# Count out parts for 4 more kits
# Order more parts to complete those kits
# Find out who wants one
# Manufacture custom dye-sub keycaps
+ Ship 4 kits out to people

---------------------------------------------------------------
It's been a few years since I posted here, it's nice to see this community is still very active!

I am currently designing a custom 50*-key keyboard to house a TI-84 Plus CE (model M 2019 or newer for the graphing and text scrolling speed boost), and turning it into a desktop calculator.

TI-84 Keyboard Edition, KE

Here is a quick mock-up done I created using keyboard-layout-editor.com, along with another coloring option:


Because of the 6 ortholinear rows, standard Cherry or OEM profile keys would be shaped odd.
I am leaning towards DSA profile flat keys, on an inclined or even slightly curved mounting plate.
(Second example, and Second-to-last example, respectively)

I tried to keep the layout pretty close to TI-84 original, partly to retain muscle memory, and partly to keep the alpha keys in the right order. The miscellaneous keys (math, apps, pgrm, stat, vars), are placed kinda far away from the right-hand number-crunching position.
The commonly-used key combos 2nd-mode, should still be pretty quick with the index/middle finger and thumb, and I may swap the XTn and DEL keys for the same reason.

The idea is similar to a Voyage 200 or TI-92, but with standard keyboard MX-style switches.
To make this a completely integrated machine, the screen needs to be detached from the motherboard, and the keys need to be wired to the keypad on the calculator motherboard.
The goal is to use a working TI-84PCE, and move all of its guts into this custom keyboard case.
The screen, after doing some reading here and here, the connector for the display has a model FH26-39S-0.3SHW, which is a 39-pin staggered 0.3mm pitch FFC cable.
So, would an extension like this Ebay listing work?

It's almost worth the 1 month delivery to try it out.
The plan is to mount the keys to a slanted/angled plate, and tuck the calculator circuit board underneath the raised rear side, laying sideways. This would require the screen cable extension to bring the screen up to the top of the case and turned 90 degrees relative calculator PCB

Keen eyed among you may have noticed 51 keys instead of the 50 keys on the TI-84.
The second key on the bottom row is for adding control for some key backlighting, or maybe some other feature, as backlighting on opaque keys in kinda pointless.
If you have an idea for what function this could be, ideas are very welcome.

Every single key will have to be custom made, as there are no TI-compatible keycap sets that I know of.
But after doing some research about custom keycaps, I think there is a pretty obvious choice: DIY Dye Sublimation.
(This is not me, but this is the process I'm thinking about)


The dye-sub printed sheets can be ordered on Etsy or maybe we can work something out within the Cemetech community, I can imagine there are other keyboard enthusiasts here.

Tracing where each key needs to be soldered to the keypad shouldn't be too hard, and hopefully in reverse-engineering the TI-84 keypad there can be some way to wire up all the keys without needing to run 100 (2 for each key) wires individually.




So, some questions I have:

1) What do you think of the layout? What key combos do you find yourself using on your calculator, and how can those be translated to this keyboard?

2) What do you think about the legends on the keys? Put the alpha-mode legends on the front edge? Just have the main key legends and do the rest by memory? Or something similar to a standard keyboard number row, with main legends on the bottom and 2nd legends on top?

3) Do you have any tips for re-wiring the whole keypad matrix to discrete switches? Is this feasible? And about the screen extension, has anyone tried this before? Is this actually a standard ribbon cable pitch? Will I get signal integrity issues when using an extension?

4) Would this be something that people in the Cemetech community would be interested in purchasing, either assembled or as a kit? I showed my brother the concept and he said it looked usable, but it would be much bulkier and novel than the pocket-able TI-84.

I'll be logging more thoughts and designs here, and eventually I might make the plunge and start buying parts.

I joined this community in highschool when I was just playing with calculators bored in class. Because of you all, I am almost done with my Electrical and Computer Engineering degrees, and have the confidence, and maybe the skillset, to pull a project like this off. Thank You!




Update:
I found a Reddit post from 8 months ago where they did a similar thing. I'll try to contact them to see about keypad wiring and screen extension.

Very cool idea - it reminds me of the KeyI-84:



https://imgur.com/a/WFCZxW2
https://www.keebtalk.com/t/gb-keyi-84-mechanical-graphing-calculator-extended-1-week-till-6-8/8754

It might be worth seeing how they did their key printing as well, though it looks as though they specialise in custom keyboards/pads?

tr1p1ea, yes, that is exaclty what it resembles. Is that a picture of your own? You hopped on that group buy? If so, nice!

I sent the KeyI-84 creators at abstractkb an email asking how they are interfacing with the CE's PCB, so maybe they can get back to me on that. I also found a source for blank keycaps, I'll post more of that as an update on this post.

Thank you for pointing me in that direction!

Quick edit, here is the source for blank DSA PBT keycaps: KBDfans DSA Blank Keycaps 1U (10pcs)

It looks like they are simply connecting to test points on the PCB that correspond to the relevant rows/colums for the keypad matrix - basically piggybacking the existing keypad.

I wonder if they have any plans available?

I see, looks like it's just test points. I can probe around with an o'scope when I crack one open. Some plans would be nice, but it's not something we can't just reverse-engineer. Should I go ahead and buy a new CE from Walmart/Target and hope it's at least a model M?

I think @Adriweb would be able to assist with identifying rev M CE's when purchasing?

This, I like this. I'm a serious mech snob, so I would love this. When do you plan on making a prototype?

I like the legends, and the layout looks good, but I'll have to do some testing with what keys I use on a daily basis, how close they are to other keys, etc... I would totally buy one of these as a kit, since it seems like a really cool project.

One suggestion though, you mentioned backlighting. Does this entail... RGB? :O How do you plan on doing the backlighting? Anyway, really cool project. Definitely going to follow this thread closely.
-Knights

I think that this the layout looks amazing. I definitely think that people would be interested in this. I would definitely look into getting this if it's built. I'm not super good at electronics, but I'd love to help with what I can. Have you started making it yet? Keep up the awesome work NoahK!

Thank you RoccoLox and KnightsWhoSayNi for the feedback. I am working on the design for now, and will start buy parts in the next few weeks.

I would love to see what key combos people most use, and how that would translate to the layout.
The keycaps will most likely be DSA, as I have found a nice source for blank keys in various colors.
Blank DSA keys here!
I chose not to go with a sculpted key like regular OEM or Cherry, because having 6 rows is difficult with a 4-row sculpted profile. That being said, DSA is not sculpted, so I am pondering using a curved or multi-angled plate to mount the switches on.


Comparison of different keyprofiles, all have 4 rows.


Comparison of OEM & SA profile (known for easiest to type on) and custom curved/tilted DSA profile with 6 rows.

All of the blue curves on the sketch there are the same radius.
Obviously, the curved option would be hard to manufacture, but maybe 3d printing is the answer? or just really good CAD and assembly.
The last option there would be the easiest "sculpted" layout, only requiring 2 different angles. I want to have the screen angled a bit to make it easier to read, like the original TI-83 and many other desktop calculators.

The other choice for uniform keycaps is XDA. XDA has a larger surface area, which would be good for these custom legends, but from what I have read online, they are harder to type on, and are much more expensive.

I talked to Ben Abstract from AbstractKB who designed and sells (sold?) the KeyI-84.
I asked him about screen ribbon cable extensions and how he wired up all the switches.
He confirmed that the ribbon cable in the top of this topic would work just fine.
He also mentioned that the PCB he designed that solders directly on the front of the CE's PCB only works with the pre-2019 models (pre model M).
I asked if it was just not possible with the newer ones, and thankfully he said that the newer models of CE just have the test points in the different locations, and too close to each other to design a piggyback PCB because of the tight tolerances.
But this does confirm that all of the row and column traces for the keypad matrix are exposed as solder-able test pads on the PCB, so no worries. All I need to do is grab an o'scope and figure out what pad does what.
Sadly, he did not offer me the schematic or pinout of the test pads, which is understandable because that is information that he spent gathering, and selling in his store.
His KeyI-84 uses DSA profile keycaps as well, so perhaps that is a good choice after all.
AbstractKB KeyI-84 keycap legend render shown here



As for RGB, well, that would be sweet-as, but kinda difficult. I am still debating whether or not to make PCB's, or just hand-solder everything.
If I do PCB's, then putting in RGB would be a breeze... as long as I can find a way to control them.
Right now, I only have one spare key that is not hooked up the the calculator.
Currently, I am planning on using that key to toggle on/off just a single color of LED, using a module like this one from Adafruit.


This module and using one color of LEDs would keep the interface clean, and not draw any power.
I want to keep the BOM pretty low, and RGB gets complicated quickly. I would need to find an RGB controller that has a one-button interface, or design my own and attempt to use a microcontroller to detect keypresses while still being transparent to the calculator. And microcontrollers eat up a lot of power. Ideally, the original battery from the CE would be used.

If anyone knows of or can find an RGB controller chip/module/circuit that only uses one button for both turning it on/off and cycling through different modes, let me know. Could also include a little slide switch for the RGB lights, but that just adds a bit of clunk and tacks more on to the BOM.

Anyway, I am going to try my hand at purchasing a new post-2019 model M+ 84CE, and reverse-engineer the keypad. I'll keep this thread updated.

Yeah it wont be hard to tap into the keypad, just means you might have to run some wires to your keyboard PCB etc - should only be 15/16 or so plus power.

There is information on the way the matrix is connected here: https://wikiti.brandonw.net/index.php?title=84PCE:Ports:A000

Also this is bad because now I'm interested in the world of custom keyboards - which might prove to be a good distraction for me lol .

Thank you for that link. I am assuming the "Using the Keypad" section coincidentally shows the physical row/column location of each key when it shows the bit/address location.

That is very useful. Now I just have to find which test pad on the PCB corresponds to which row/column.

And yeah, this is partly just a huge distraction.
I have to keep justifying working on this project because I keep associating it with just distracting myself from "real work".
But, in fact, designing PCB's, doing CAD modeling, practicing my reverse-engineering skills, documenting my findings, reaching out to strangers for help/input, and learning something new (dye sublimation), are all skills that do help me out professionally, and build my confidence in my hobbies and knowledge.

So, not a distraction, but a learning and self-improving experience.

This may be a double-post, but I think this is a bit of a different idea and warrants a post of it's own.

I have been thinking about the layout, especially about the 2nd/Mode/Alpha/XTn cluster. These 4 buttons are what most games and programs use for control, using the left thumb. The right thumb has the arrow keys. This lets the calculator be held like a gameboy, and is the most common control scheme.



Here is what that looks like on the current layout:


And here are some alternatives:
Option 1, Top Cluster:

Option 2, Lower Left Cluster:


The original design looks good with the color scheme and makes 2nd and alpha really easy to press, while also keeping good alphabet continuity. But Mode and XTn are very far away from 2nd and alpha, which makes 2nd-alpha or 2nd-mode controlled programs difficult.

Option 1 has the 4-key cluster where it would be naturally when doing math operations, and having the XTn key close by makes for easy equation-punching. But as a right-handed person, using the arrow keys and that cluster at the same time is a bit difficult, with what looks like would be a very cramped experience, left hand on top. This layout also breaks up the alphabet, but keeps the color scheme and organization clean.

Option 2 places the 4-key cluster to the lower left. This would be ideal for 2-handed cluster-arrowkey programs and games, so no hands have to cross each other and the screen is placed right above. This also makes the alphabet keys very continuous, even more so than the original layout. But, for doing math, the puts the 2nd, mode, and XTn keys farther away, but maybe using 2 hands is a goo compromise? I think I use 2 hands normally.

For me, option 2 is the best so far. I use my calculator with 2 hands, so it makes sense to me. But this is also a desktop calculator now, not a handheld, so I may want to just use it with one hand... Only time will tell.

The other thing that needs some experimenting with are the DEL, CLEAR, VARS, STAT, and ON keys. I would like to keep ON in the bottom row, and VARS and STAT are barely used by anyone (correct me if you use VARS and STAT more than just to get through statistics class...).
But DEL and CLEAR are pretty important! I use 2nd-DEL for insert all the time, so I may move that down to beside MODE on Option 2. Putting clear where delete is, just above the arrow keys, makes it really easy to access when doing math, where I find myself using clear a lot to erase lines when I make mistakes. But IDK.

I would love your feedback on some of these layouts, and where you think keys should go. I think the initial prototype will be hand-wired, so we can play around with layouts before making a PCB.

I was going to suggest that a lot of programs (and particularly games) user arrows + 2nd/alpha for controls which would be difficult with Option 1 - So I think Option 2 is a good fit.

I also love the render on the main post! How would you make the PCB if it's curved btw?

Thanks for your input on Option 2, I am growing to like it a bit.
I think I have settled on a layout, moved some of the del/clear/stat keys:


I think I will try to put the alpha legends on the front face of the keys, and make the main legend large and centered.


As for the Curved PCB... I think I will just have to make 6 separate PCBs, and butt them against eachother, maybe soldering on the touching edges like a weld bead. Maybe make the edges have interlocking fingers so the solder can hold stronger? And break up the soldered edge so traces and routes can jump from one PCB to the next? Would have to use some sort of form or jig to get things aligned properly, and make some sort of structure to keep it rigid when assembled.

That's kinda why I'm leaning towards a single flat or maybe just 2 different angles, would make CAD and assembly a lot easier, especially if I end up shipping this to a few people as kits.

I agree that a flat KB is probably the way to go - most PC keyboards are flat, and use keycaps for profiling. I use a 6/7-row flat DSA keyboard sometimes, and it's ok.

I've also seen designs, especially for low-volume stuff, which don't use a PCB at all - they just used diodes and pieces of wire to make the keyboard matrix. You could 3d print the plate/case, though it's starting to get quite big for that.

Solder-together designs are probably not a good way to go, unless there's significant stiffening. I suspect PCB delamination at the joints would be a problem. I don't know of any curved/multi-board designs offhand; the only mechanical board with profile from a curved matrix I can come up with is the model M, which has a curved membrane. I'm not sure about the F, though.

I would discourage separate PCB's and possibly look into flexible PCB's such as: https://www.pcbway.com/flexible.aspx or similar. The pricing is more expensive so it depends on your budget - note I haven't ever ordered a flexible PCB before but I've definitely bought a few kits that have used them.

Hooloovoo, I have to agree with you. If I am going to use a PCB, it should be flat. And if this is going to be portable in the slightest, being flat is also the way to go, maybe with a flip-up screen or something.

But at the same time, There needs to be enough space under the keys to fit the calculator PCB and all the wires. So, being portable probably won't be an end-goal.

I don't have access to a 3d printer that is going to be big enough to print the whole thing, but if I did, then that would make the curved design work alright. But that would also mean a hand-wired matrix, because of the lack of PCB, which is not sellable.

Solder-together design could be stiff enough, with enough reinforcements and orthogonal PCB's as well, like soldering together a box with corners. Could make the whole thing out of PCB! That would look pretty sick. But also kinda expensive.

Practically, flat makes sense. But man does that curve look good!


And tr1p1ea, a flexible might work for getting all the wires together, but I would have to rely on a really good case design for rigidity, as the flex PCB's are prone to tearing (?citation needed?). But that is an interesting solution...

The curve looks great, we were talking on IRC about the possibility of custom resin 3D printed caps that could have varying heights to simulate a curved profile PCB instead? I now there are lots of etsy-ers that can print this kind of stuff.

Resin printing might not be a bad idea, but butting legends on resin prints may be difficult. I have a friend who has a resin printer, so I could probably work something out.
Would have to do some research about getting resin prints to have the right color and legends.

On the other hand, here is a render of it flat, with some feet and an angled screen:



And here is tr1p1ea's qwerty-style calc keyboard, would be a fun addition:



I think I am going to go with flat, where custom keycaps could get the profile we need.

Instead of directly mapping buttons to the calculator's buttons, you could probably achieve a nice QWERTY layout with a sensible calculator layout if you put a middle ground in place, like an arduino or something, it would convert the sensible keyboard layout to the calculator's standard layout.