Tandy 2800 HD keyboard mod? (Alps keyswitches)

[skunkette]

The keyboard itself!

IMG_2421.JPG (1.02 MiB) Viewed 1639 times

Hello all,

I am attempting to rebuild a broken Tandy 2800 HD laptop to contain modern components, but I wish to retain the amazing keyboard it came with, featuring Alps keyswitches.

I am an experienced coder with some maker experience, but I have never attempted this kind of mod before. Therefore, I may need a little hand-holding. Links to relevant HOWTOs for similar projects would probably help.

Here's what I have learned.

The keyboard itself is an 84-key keyboard with "true 101-key emulation mode", featuring Alps keyswitches.

It interfaces with the motherboard via a 30-pin ribbon cable which is 1.5 inches wide (0.27mm / 0.05 inch pitch). I have already sourced and ordered a header to let me interface with this cable, with the goal of plugging it into a Raspberry Pi, Arduino, Teensy, or similar device to attempt to reverse-engineer how this thing works. (I know this is a wildly ambitious goal and that I will need lots of help, but, well, that is why I'm here *humble smile*)

I searched the motherboard for a keyboard controller chip; however, the closest I found was an NEC D8749HC. Per the datasheet on https://www.alldatasheet.com/view.jsp?S ... C&sField=3 this is a "High-Speed, 8-Bit, Single-Chip Hmos Microcomputers"... in other words, a general-purpose microcontroller, and not a dedicated keyboard controller chip.

This is quite disappointing; I was hoping the keyboard would be interfaced with some sort of dedicated keyboard controller chip which I could simply source and interface with an Arduino/Teensy/RaspPI and go about my merry way.

Keyboard interface with motherboard

IMG_2417.jpg (934.24 KiB) Viewed 1639 times

One problem I've immediately found is that, while there are 30 pins on the cable coming out of this keyboard, Raspberry Pis, Arduinos, and Teensys do not have 30 GPIO pins Will I need something like this? https://www.amazon.com/dp/B06WWRZ7PS/re ... UTF8&psc=1 Or is it likely that many of those 30 pins aren't even used?

I have no idea if I am attempting to re-invent a wheel here, or if there is an existing controller/interface board that would help me.

At this point, any advice would be much appreciated. I could always resort to switching to a different keyboard that fits in the same space, but I'd really rather keep the original Tandy 'board.

What should be the first step of my work here? I've been assuming it would be something like "interface all 30 pins to a pi or something, and attempt to reverse-engineer what kind of keyboard matrix is in use here."

[Nuum]

Are there any chips on the keyboard part?
If not, the row and columns of the keyboard are most likely directly accessible from the ribbon cable. 30 pins would be plenty for all rows, columns and the LEDs.
I'd try to find the matrix of rows and columns first by probing every switch and seeing which pin each side of the switch connects to. One side will connect to a row pin, the other one to a column pin, but be careful with the diodes, they might make it harder to find the corresponding pins.

Sorry if this sounds confusing, I've only ever done this once myself!

[skunkette]

No chips whatsoever on the keyboard part.

I found out that a Teensy++ has over 30 GPIO pins! So I've ordered a Teensy++ with pins and a breadboard, and I am going to start experimenting. B-)

[skunkette]

It loooooks like once I figure out the matrix of this particular keyboard (which I will post here, of course!), all I need to do is modify the firmware from workshop-f7/how-to-build-your-very-own- ... t7177.html and Bob shall be my uncle.

Here's hoping.

[kokokoy]

If you don't need complex features or code these GUI based builder can help you out once you figured out your matrix

building your layout -> http://www.keyboard-layout-editor.com/
compiling your hex -> http://kbfirmware.com/