Hovert60 keyboard devlog #1: Init

Making a low-profile wireless split keyboard from scratch. I also intend to handwire it rather than use a PCB.

7 minutes

Apr 10, 2024

Table of Contents

Background

I have been a mild fan of mechanical and ergonomic keyboards for a while now. I have used Ergodox EZ, Planck EZ ¹ and OLKB Preonic. Additionally, my XKB configuration is somewhat interesting.

You see, Russian alphabet has 33 letters, while English only has 26. This means that on the default Russian layout more keys are used for letters, and punctuation keys are different from the US layout.

To improve the multilingual typing experience, a variant of the RU layout called unipunct was created by @a13. I then modified it slightly and submitted it to xkeyboard-config. The layout moves some of the RU keys to a «Layer 3» so they can be accessed when a «Layer 3 modifier» is held.

For example, letter ё [jɵ] is kind of an extension of letter о [o]. As ё is used relatively rarely (and some people even consider it optional), it is placed on the Layer 3 of the о key. My Layer 3 modifier is Right Alt, so I can type ё by pressing RAlt+о and Ё by pressing RAlt+Shift+о.

Example XKB configuration that uses the layout

/etc/X11/xorg.conf.d/10-user-keyboard.conf

Section "InputClass"
    Identifier "system-keyboard"
    MatchIsKeyboard "on"

    Option "XkbLayout" "us,ru"
    Option "XkbVariant" ",unipunct"

    Option "XkbOptions" "grp:caps_toggle,lv3:ralt_switch"
EndSection

lv3:ralt_switch or an alternative lv3:... option is necessary to configure the key that will be used as the Layer 3 modifier.

Optional grp:caps_toggle configures language («group») switching to be done with Caps Lock. Caps Lock can still be activated if pressed with Shift. It can also be replaced with ctrl:swapcaps,grp:lctrl_toggle to make Caps Lock behave as Ctrl, and make Ctrl change the language.

Note: at the moment of writing, localectl list-x11-keymap-variants ru does not display the unipunct variant. I might look into this at some point.

Note: the settings can also be hand-clicked in something like KDE keyboard configuration. And they can also be used in input configuration of something like sway if you use Wayland.

I should mention that keyboard layout configuration does not end with XKB config. It can also be configured by modifying keyboard firmware, and some use cases really benefit from configuring both. However, this is a whole another topic which I will save for later. I plan to write more about this as a part of my Lazy keymap project.

So, considering my experience of using «ergonomic» keyboards and ru(unipunct) layout, I felt like I can improve something. This, along with the aforementioned lazy-keymap, is what this devlog is about.

Idea

This is the idea I started with:

Make a keyboard tailored for me:
Low-profile
Ortholinear or column-staggered ²
Ideally wireless
Ideally with a thumb cluster
Possibly split

The «tailored for me» part implies a few additional requirements. They basically boil down to what keys and key combinations I want to have the quickest access to.

Some accessibility criteria for keys & key combinations

Feature	What it makes easier
Dedicated number row	Typing numbers & symbols, using Fn-keys & number shortcuts
`Caps Lock`	Changing language
`Shift` combos	Big letters and symbols
`Ctrl [+ Shift]` combos	Regular application shortcuts
`Super³ [+ Shift]` combos	Window manager shortcuts
`Right Alt [+ Shift]` combos	Typing in Russian

With this in mind, there are only two things left to do before I can start:

Find inspiration
Choose implementation approach

Inspiration

These keyboards served as my inspiration:

Sofle is probably the closest to what I want to make.

Approach

A keyboard can be designed in many ways that have various difficulty levels.

The approach of my choice is:

Design the front plate shape in Autodesk Fusion from scratch
Cut the front plate out of a sheet of metal using a CNC router
Solder the key switches by hand, without using a PCB

To be fair, my initial idea was to cut the front plate out of wood or acrylic using a laser cutter. However, I learned that with the thickness of material I need to use, the result would be very fragile and wobbly. Maybe it could work if I used a PCB to hold the switches in place, but I don’t want that.

Here are some links:

An amazing in-depth keyboard handwiring guide by Ewen Cluney
Another keyboard handwiring guide with amazing photos by @cribbit
A multi-part handwiring guide with nice extra info by Matteo Spinelli
Sofle Choc build guide (uses a PCB)

It’s also important to mention that there are tools that can make the design process significantly easier:

Keyboard Layout Editor
Ergogen and its unofficial deployment which is «better» ⁴
Cosmos (no idea about this one but looks very cool)
Others not mentioned…

I didn’t use these helper tools because I was not aware about them when I started, and later Autodesk Fusion was just too fun to drop.

Preparation

Choosing the parts

There was a number of decisions to make:

What key switches to use?
What material to use for the front plate that will hold the switches locked in place?
What microcontroller and firmware to use?
How to attach the microcontroller to the board?

Choice of key switches

Decision process – keyswitches

As the goal is to make the keyboard low-profile, the «default» option seems to be Kailh Choc switches. It’s important to note that there are 2 main versions of Kailh Choc switches – V1 and V2. Kailh Choc V1 keycaps are not compatible with V2 and other switches.

Another important thing is that Kailh Choc keycaps are usually spaced differently compared to more traditional Cherry MX switches & keycaps. You can read more on Deskthority Wiki: Kailh PG1350 #Keycaps. There is also a datasheet for them.

Key (ha!) takeaways:

The cutout for the switch is 14×14mm
One unit (area taken up by a key) is 18×17mm (compared to the more common 19.05×19.05mm)
For the switches to click in place, the plate should ideally be 1.3mm thick (compared to the more common 1.5mm)

I purchased Kailh Choc V1 Pink switches along with keycaps for them.

Kailh Choc V1 switches next to Cherry MX style switches

Choice of front plate material

Decision process – plate material

As I mentioned previously, wood and acrylic are pretty much out of the question.

Aluminium? I don’t like how it feels in my imagination, so no.
Brass? Yes. Totally not inspired by DIY Perks.

I purchased 2 brass sheets with the dimensions 150×150×1.5mm.

Choice of microcontroller and firmware

Decision process – microcontroller

As I want to build a wireless keyboard, using ZMK for the firmware seems to be a good idea. Looking through the list of hardware supported by ZMK, I was choosing between Pro Micro and Seeed XIAO microcontroller «footprints». An important detail is that not all microcontrollers support BLE, and I wanted one that does support it (so I don’t have to charge the keyboard as often).

Note that the controller is quite small. It actually barely has enough pins for all the keys I want to have! Looking ahead, there are going to be 30 keys soldered in a 5x6 matrix, which means I need 11 I/O pins.

In the end I selected Seeed XIAO BLE that uses an nRF52840 chip.

Determining how to attach the microcontrollers to the boards

Decision process – microcontroller attachment

Originally I was thinking about glueing the microcontroller to the bottom board, or maybe leaving it hanging, as it doesn’t have any mounting holes. But I realized I can use a soldering breadboard to mount the microcontroller and connect the wires to it.

This brings additional benefits:

If I use header pins for the microcontroller, it becomes swappable (in case it fails)
I can hide the battery under the breadboard
It’s easier to fix issues during assembly

Final list of parts

Component	Count
Seeed Xiao nRF52840 (BLE)	2
Kailh Choc Pink switches	60
Blank White Keycaps	58
Blank White Homing Keycaps	2
Brass plate `150×150×1.5mm`	2
`1N4148` Diodes	60
`250mAh` Battery	2
Battery cables	2
Breadboard	2
`AWG 18` Copper wire	long
Heat Shrink tube	long
`M2` Standoffs & Screws	many
Header pins and sockets	many
Sheets of acrylic (for prototyping)	few

Naming

The name of the project, Hovert60 or h/t60, highlights several project features:

Hover: the keys are held by the front plate, there is no additional support from a PCB
Hover: the switches have very low resistance, so typing experience will be very light
Overt: the keyboard enclosure is open from the sides
Overt: the development process is documented here
60: There are 60 keys

What’s next

I plan the following posts after this one:

Design process – post #2
Manufacture
Configuration

Planck EZ was retired in 2023, but just Planck still exists ↩︎
Read about Staggering #Columnar layout on Deskthority ↩︎
«Super» is an alternative name of the «Windows» or «Command» key, also known as «Meta». Read more about Super key on Wikipedia. ↩︎
Github – ergogen ↩︎