Step One: Case Design
Step Two: 3D Printing
Step Three: Insert the Key Switches and Stabilizers
Step Four: Wiring
Step Five: Program the Pico
Step Six: Assemble the Keyboard

Published September 22, 2021 © CC BY-NC-SA

The Expletive Keyboard

I built a keyboard that contains only the letters you really need.

IntermediateFull instructions provided2 hours10,515

Things used in this project

Hardware components

Raspberry Pi Pico

Cherry MX Key Switches

Key Stabilizers

Key Caps

Hand tools and fabrication machines

3D Printer (generic)

Soldering iron (generic)

Story

A month or two ago, I was browsing Instagram and saw the post in the screenshot. It was what appeared to be a photoshopped keyboard that only contained the letters necessary to tell someone off. I thought it was funny and decided to build a real, functional version. This is the result!

It does, indeed, work. Plug it into a computer's USB port and it will show up like any other keyboard. Other than the important letters, there is also a space key, a backspace key, and an enter key. The enter is actually a "+" meant for the numpad, which I used because I design the case with the wrong measurement for a normal enter key (2u instead of 2.25u).

A note on key caps:

The key caps for this project are tricky. Most key caps are shaped depending on the row each key sits in. So your "Y" key is shaped differently than your "K" key. This is a problem, since the keys won't be in normal locations here. For this reason, you need uniform key caps. Both XDA and DSA profile key caps are uniform. Furthermore, because this keyboard required two "U" keys and key cap sets only come with one, I found a set where the numpad asterisk was the same color as the alphanumeric keys.

Also keep in mind that key switches are either PCB-mount or plate-mount. You need plate-mount switches for this project. The same goes for the stabilizers.

Step One: Case Design

I designed the enclosure in Autodesk Fusion 360. The top plate, where the key switches mount, is integrated into the enclosure. The biggest challenge here was the shape of each key switch hole and its spacing, along with the holes for the stabilizers. You can find more information about those at the following links:

https://null-src.com/posts/keyboard-design-cheatsheet/post.php

https://geekhack.org/index.php?topic=64287.0

https://switchandclick.com/stabilizer-guide/

https://user-images.githubusercontent.com/13644/66226900-eb1e3e00-e6a9-11e9-80fa-fce8996ba06b.png

In my case, the switch holes are just square and that worked fine.

Step Two: 3D Printing

I printed the main part of the enclosure (top.stl) using an UNIZ IBEE MSLA resin 3D printing, to ensure that it was smooth and free of layer lines. The bottom (bottom.stl) I printed on a standard FFF 3D printer to save resin.

You can print both using either type of printer.

Step Three: Insert the Key Switches and Stabilizers

This step is pretty straightforward. First, put in your stabilizers. Each stabilizer has five pieces: the metal rod, two bases (purple here), and two moving bits (green here). It helps to assemble them first, then push them into place.

After that, you can pop in the key switches. I inserted them all with the "Cherry MX" logos towards the top.

Step Four: Wiring

I essentially just copied the wiring here: https://www.hackster.io/Mukesh_Sankhla/pico-keypad-ea42a8

One pin of each key switch will go to the Raspberry Pi Pico's 3v3 pin. I used a single stripped wire for all of those pins.

Then each key switch's second pin will connect individually to a GPIO pin on the PICO. I used the following pins:

GP2 (backspace)
GP3 (K)
GP4 (C)
GP6 (U)
GP7 (F)
GP8 (Y)
GP10 (O)
GP11 (U)
GP12 (enter)
GP13 (space)

Step Five: Program the Pico

For detailed instructions, check here: https://www.hackster.io/Mukesh_Sankhla/pico-keypad-ea42a8

But these are the basic steps:

Copy the CircuitPython UF2 file onto the Pico drive
Copy the Adafruit_HID library folder into the Pico's lib folder
Copy the code.py file from here onto the root of the Pico drive

Step Six: Assemble the Keyboard

Once you verify that the keyboard is working properly, you can assemble everything.

Start by pressing all of the key caps into place.

Then cover the Pico's pins in electrical tape to protect. I didn't bother to design a proper mount, so the Pico is loose inside of the enclosure.

Finally, use 4 M3x8 screws to attached the bottom cover, taking care to feed the Pico's USB cable through the slot.

If you want, you can use paint to fill in the logo like I did.

And you're done! Now you've got a keyboard that only has the letters that you really need.

Code

code.py

import time
import digitalio
import board
import usb_hid
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keycode import Keycode
from adafruit_hid.mouse import Mouse

btn1_pin=board.GP2
btn2_pin=board.GP3
btn3_pin=board.GP4
btn4_pin=board.GP6
btn5_pin=board.GP7
btn6_pin=board.GP8
btn7_pin=board.GP10
btn8_pin=board.GP11
btn9_pin=board.GP12
btn10_pin=board.GP13

keyboard = Keyboard(usb_hid.devices)
mouse = Mouse(usb_hid.devices)

btn1 = digitalio.DigitalInOut(btn1_pin)
btn2 = digitalio.DigitalInOut(btn2_pin)
btn3 = digitalio.DigitalInOut(btn3_pin)
btn4 = digitalio.DigitalInOut(btn4_pin)
btn5 = digitalio.DigitalInOut(btn5_pin)
btn6 = digitalio.DigitalInOut(btn6_pin)
btn7 = digitalio.DigitalInOut(btn7_pin)
btn8 = digitalio.DigitalInOut(btn8_pin)
btn9 = digitalio.DigitalInOut(btn9_pin)
btn10 = digitalio.DigitalInOut(btn10_pin)

btn1.direction = digitalio.Direction.INPUT
btn2.direction = digitalio.Direction.INPUT
btn3.direction = digitalio.Direction.INPUT
btn4.direction = digitalio.Direction.INPUT
btn5.direction = digitalio.Direction.INPUT
btn6.direction = digitalio.Direction.INPUT
btn7.direction = digitalio.Direction.INPUT
btn8.direction = digitalio.Direction.INPUT
btn9.direction = digitalio.Direction.INPUT
btn10.direction = digitalio.Direction.INPUT

btn1.pull = digitalio.Pull.DOWN
btn2.pull = digitalio.Pull.DOWN
btn3.pull = digitalio.Pull.DOWN
btn4.pull = digitalio.Pull.DOWN
btn5.pull = digitalio.Pull.DOWN
btn6.pull = digitalio.Pull.DOWN
btn7.pull = digitalio.Pull.DOWN
btn8.pull = digitalio.Pull.DOWN
btn9.pull = digitalio.Pull.DOWN
btn10.pull = digitalio.Pull.DOWN

while True:

    if btn1.value:
        print("Button 1 pressed")
        keyboard.press(Keycode.LEFT_SHIFT,Keycode.F)
        time.sleep(0.05)
        keyboard.release(Keycode.LEFT_SHIFT,Keycode.F)

    if btn2.value:
        print("Button 2 pressed")
        keyboard.press(Keycode.LEFT_SHIFT,Keycode.U)
        time.sleep(0.05)
        keyboard.release(Keycode.LEFT_SHIFT,Keycode.U)

    if btn3.value:
        print("Button 3 pressed")
        keyboard.press(Keycode.LEFT_SHIFT,Keycode.C)
        time.sleep(0.05)
        keyboard.release(Keycode.LEFT_SHIFT,Keycode.C)

    if btn4.value:
        print("Button 4 pressed")
        keyboard.press(Keycode.LEFT_SHIFT,Keycode.K)
        time.sleep(0.05)
        keyboard.release(Keycode.LEFT_SHIFT,Keycode.K)

    if btn5.value:
        print("Button 5 pressed")
        keyboard.press(Keycode.BACKSPACE)
        time.sleep(0.05)
        keyboard.release(Keycode.BACKSPACE)

    if btn6.value:
        print("Button 6 pressed")
        keyboard.press(Keycode.ENTER)
        time.sleep(0.05)
        keyboard.release(Keycode.ENTER)

    if btn7.value:
        print("Button 7 pressed")
        keyboard.press(Keycode.LEFT_SHIFT,Keycode.U)
        time.sleep(0.05)
        keyboard.release(Keycode.LEFT_SHIFT,Keycode.U)

    if btn8.value:
        print("Button 8 pressed")
        keyboard.press(Keycode.LEFT_SHIFT,Keycode.O)
        time.sleep(0.05)
        keyboard.release(Keycode.LEFT_SHIFT,Keycode.O)

    if btn9.value:
        print("Button 9 pressed")
        keyboard.press(Keycode.LEFT_SHIFT,Keycode.Y)
        time.sleep(0.05)
        keyboard.release(Keycode.LEFT_SHIFT,Keycode.Y)

    if btn10.value:
        print("Button 10 pressed")
        keyboard.press(Keycode.SPACE)
        time.sleep(0.05)
        keyboard.release(Keycode.SPACE)

    time.sleep(0.1)

Credits

Cameron Coward

17 projects • 1398 followers

Writer for Hackster News. Proud husband and dog dad. Maker and serial hobbyist. Check out my YouTube channel: Serial Hobbyism

The Expletive Keyboard