Arduino/Teensy/Whatever Micro-controller DIY keyboard

There's some info on converting the keyboards of old 8 bit machines to usb that might be relevant to your needs here. Most 8 bit machines had keyboards that were nothing more than a matrix of switches so adapting the concept to suit your needs will be fairly straightforward.

More info:

http://shiggyenterprises.wordpress.com/2012/10/21/how-to-create-your-own-keyboard-from-scratch-arduino-uno-and-power-part-1/

Building a new and improved keyboard from scratch | ITProPortal.com

If all else fails, just Google 'diy keyboard' - I built a usb ZX Spectrum keyboard myself for my RPi project, but that's all I did.

A point to note- even a cheap keyboard will be way better than an actually home built one and it will cost a lot of time and money.

But if you still want to make it, here are a few things:

-An odinary microcontroller will not have enough of IO until it is huge. So you would consider to use a shift register which runs of I2C

-You could use it with bluethoot.

-You would like to use a HID(Human Interface Device) controller like Arduino micro or adafruit's Pro Trinket micrcontroller.

Hope it helps.

I've written up a conversion of an Acorn Electron into a USB keyboard on Instructables, here: Acorn Electron USB keyboard

This uses a Freescale KL25Z dev board - see FRDM-KL25Z - FREESCALE SEMICONDUCTOR - ARM, KINETIS, KL25Z, FREEDOM DEV | Farnell UK - which is absolute overkill (48MHz Cortex-M0) for a keyboard scanner, but it has plenty of I/O and is super-cheap.

You can browse the source for this here: https://mbed.org/users/IH/code/electron_kbd/ - the comment at the top of main.cpp has quite a bit of explanation as to how it works and how to customise it for other keyboard layouts.

Do you think an arduino pro mini could work? I'm not sue if it has enough pins, But I've got one lying around here. I am also considering using a dirt-cheap keyboard's own controller and a custom matrix, give or take some keys. I'm making this for a raspberry pi thing you see, and I need something small, but not as small as some micro keyboards.

Using the controller from a keyboard is certainly the cheapest option, and the easiest if you don't mind wiring your own matrix. I ended up utilising the controller from a cheap USB rubber 'waterproof' keyboard in a very similar way when building my ZX Spectrum project. Though I experimented with using a microcontroller, in the end I plumped for connecting the original membrane to the pins of the controller combined with a custom keymap .

How did you adapt the board to your custom key map? I was thinking of doing something similar until I saw just how confusing the matrix is inside a generic keyboard. I'm not sure where or what to cut to get just the keys I want.

That part was made easy for me because I was connecting an pre-existing matrix to the controller (from the Spectrum), then all I had to do was remap the keys through trial and error. Quite a few examples I have seen (Google 'diy keyboard matrix') are built using tactile keyswitches on a piece of proto-board, though my initial tests to find the best positions to solder the keyboard 'rows' to the controller were performed by simply shorting pairs of pins/pads with a piece of wire to see what keypresses were produced.

So, for the matrix you used everything was just simple rows and columns? I've looked inside a keyboard or two and the matrices seem more like a maze than a circuit.

How many ADC's can you have on that micro controller?

Forgive me, but would this not be an option also? If there are enough ADC's that is.

I was working on a similar project, using a 430 MCU and it worked fine.

Please let me know if this will not work, this set up uses a few resistors, and a supply of power to

key-log.

This is just a quick ruff draft, just for an example, but if the MCU has 5 ADC pins, i think this may be

a viable option Peter.