A programmable mechanical keypad with OLED display and RGB backlight.
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README.md

kbord: Programmable Mechanical Keypad with RGB Backlight

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kbord is a programmable keypad with 15 mechanical keys, each of which can be set to execute a script when pressed.

The script can be as simple as shortcut keys like ctrl+c, or as complex as creating root backdoors or grabbing passwords. Anything that can be done on keyboard can be written in the script.

Multiple profiles are supported, for different programs/environments.

Features

  • 15 mechanical switches
  • Individually addressable RGB backlights with animations
  • OLED screen displaying current profile and key functions
  • SD card script storage
  • Standard duckyscript parsed onboard
  • Multiple profiles supported

Video

Here's a silly video showing kbord in action, as well as the timelapse of me building it.

https://www.youtube.com/watch?v=EGLLCtRuEuM

Technical notes

The microcontroller used here is a STM32F072C8T6, my go-to chip when doing not-too-demanding projects like this. It costs less than a dollar, has more peripherals, plenty of pins, and is faster than any old aduinos can dream of. ST provides a free Keil MDK license with no code size limit for all F0 parts too. There are also completely open source toolchains like arm-gcc.

Since there are only 15 buttons, I didn't use matrix scanning and just hooked them all up to the microcontroller. I also included 2 rotary encoders, but they turned out to be not really useful for me so I didn't solder them on.

One interesting design detail is about the RGB LED. The WS2812(and its clones) requires a rather high data rate, around 800KHz if I recall correctly. Arduino library achieve this by bitbanging in assembly because of the predictive instruction execution time in the 8-bit microprocessors. However the ARM processor in STM32 have some funky pipeline and caches, making asm timing somewhat unreliable. As a result I turned to SPI for LED control. By selecting the right speed and carefully timing what data you send on the MISO line, you can have the waveform look exactly like what WS2812 requires. In this case sending 0xf8 at 8MHz is bit 1, and sending 0xc0 results in a bit 0. Since SPI is also used by SD card, an AND gate is added between MOSI and WS2812 input so the LED command is insulated from SPI when it's used for SD card.

Questions?

Feel free to ask in the issue section, or email me at dekunukem__gmail__com.

Usage

Step 1: Preparing profiles

Profiles are created as folders, with naming conventions like profile#_name, where # is the profile number, and name being the name of the profile. Here are some examples:

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Step 2: Preparing scripts

Now you're ready to write some scripts inside the profile folders. The script used in this project is Duckyscript, click here to read its usage.

Each key has its own script file, named like key#_name.txt, where # is the key number(top left is 1, bottom right is 15), and name is a short description of what that key does.

Here are some examples:

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The screen will only display the first 7 characters of the key name, so keep it short!

Step 3: (OPTIONAL) Set backlight color

This step is optional, but who would want to pass that? It's RGB after all.

Just create file named config.txt and set its content like this

BG_COLOR 255 100 0
KEYDOWN_COLOR 100 0 255

BG_COLOR is the background color, the following numbers are value of the color that you can change, between 0 and 255, in the order of R-G-B.

Similarly, KEYDOWN_COLOR is the color for the key to change to when you press it down.

The content of the profile folder should now look like this:

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If you skip this step the default backlight color would be light blue.

Step 4: Run it!

Format a SD card in FAT32, put all the profile folders in the root of the SD card, and insert it in the SD slot.

kbord should start up with the first profile, displaying the profile names and key names, as well as the background color:

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Press the corresponding keys to execute their scripts, if there is an error it will show up on the screen.

Press + - button on the lower right to change profiles.

More examples!

See here for some profiles that has been already set up. You can start from there and make changes to suit your need.

Making one yourself

BOM is here, build process is here

Here are some things to keep in mind if you're making one yourself:

Circuit board

The board is a simple 2-layer board with a cutout for the OLED screen in the milling layer, some board fabs might ignore that layer, so be careful.

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Getting a stencil is strongly recommended, because the RGB LED used here WILL melt if you try to solder it with a regular soldering iron. It's best to use a stencil and then reflow it in an oven.

Speaking of which...

RGB LED

The RGB LED is the trusty WS2812 that's thrown into every single RGB project these days, except it isn't: What I used is SK6812 which is a compatible clone with allegedly better performance. It is also the smaller 3535 package, not the regular 5050 kind, so do watch out for that.

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I haven't tested WS2812 with the design, it should work on paper, but I suggest just get some 3535 SK6812 and be done with it.

Switches

In theory you can use any cherry MX style 3-pin switches you like, however, because there are backlights underneath, you need to find one that has an opening for the LED, and has a clear case to let the light shine through.

I used Gateron RGB switches, they are perfectly designed for this kind of usage, translucent case with a large opening for LED. I used greens but there are other colors to choose from as well.

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A switch plate is strongly recommended, to improve stability and even out the backlight. I had mine laser cut with a diffuser material.

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Keycaps

I bought some blank white keycaps, just make sure they don't block the backlight.

Misc

Remember to make sure the entire board is working, as well as install the standoffs before you solder the switches in place, otherwise it would be almost impossible to get them off again.