Built a Keyball44

##Introduction

One of my goals over the New Year holidays was to build a Keyball. The keyboard I built is the Keyball44. It is a well-known keyboard among people who have built or are considering custom keyboards.

I use a Keyball66 as my daily driver because the larger key count gives convenience and a feel focused on typing, but I wanted to build at least one Keyball for the looks. As I gradually used smaller keyboards, I realized that just over 40 keys is enough. If I learn to use multiple layers well, even the Keyball39 might be enough, but I have never used a keyboard with five rows on the left hand, so I decided to start with the Keyball44, which has the same number of rows as the Keyball66.

This time I focused on the concept rather than the typing feel. The concept is clear: make it all white.

As of 2025/01/04, the case and trackball had not arrived yet, so I plan to update this article once everything is assembled.

##Build

Here is the build. As mentioned, everything is white.

Total: 58,399 JPY.

Too expensive...

If I skip the case and choose more reasonable keycaps, I could probably keep it around 35,000 JPY. Or if I had a 3D printer at home...

##Photos

I will add photos once all parts arrive.

##Troubles

I've built several keyboards, and every time I run into issues. This time I hit three main problems.

###Weak soldering or missing joints

I only solder when building custom keyboards, but even with multiple builds under my belt and a second Keyball, I still had soldering trouble. This was largely caused by the second issue below, but after finishing the build, three keys did not respond when I pressed the switches. The build guide says to flash a test firmware and check operation after soldering everything except the trackball section. I followed the steps and tested each key to make sure it registered (apparently it didn't...). I used the keyboard test site and tweezers to check continuity for each key and confirm each key registered at least once.

Normally I would check continuity with a digital multimeter before connecting to a PC, but as mentioned below, the battery was dead. So I only checked whether characters appeared when connected to a PC, and that was not enough.

###Dead battery in the digital multimeter

A multimeter is not essential for building a keyboard, but it makes it easy to find weak or missing solder joints, so I usually use a DT83B for continuity checks. However, I apparently left it on last time, so the battery died and I couldn't use it this time. I could have waited for a new battery before building, but I wanted to finish during the holiday break, so I pushed ahead and it backfired.

The DT83B uses an uncommon AAAA battery, which I didn't have, so I ordered one from Amazon. Next time I build a keyboard, I should be able to use the tester.

###Notes on ball bearing switches

Finally, the key switches. I originally wanted to use Roller Linear Switches, but it didn't go well. Roller Linear Switches are a newer type of switch with ball bearings built into the mechanism. Another switch with the same mechanism is WS Pearl Switch.

This can also happen with non-ball-bearing switches, but if pressure is applied from the side, the stem can rub against the housing and not return smoothly. This can also happen when the stem shape is BOX or round and the keycap cross is mismatched. In my case, some keys were slow to return after being pressed, possibly due to top plate tolerances, so I decided not to use ball bearing switches.

The same switches worked fine on a Tofu60, so the case is clearly the issue. It can't be helped, but it was good to learn that ball bearing switches can have this problem.

##Keymap

Finally, I will share my keymap. I hope it helps those who are about to decide their keymap, or those who started using Keyball but are not satisfied with their current map.

I do not use the automatic mouse layer when using a Keyball. With tuning it might be avoidable, but I find it annoying when the layer switches unexpectedly if my hand touches the ball, and I also dislike having to wait a moment after using the ball before returning to the original layer. So I switch layers by pressing keys for left and right clicks. Where to place those keys is important, so I will explain how I arranged each layer.

The base idea is to keep the layout close to regular QWERTY. I use three layers. If I add more, I don't make use of them, so three is enough. As I gradually map more keys and reduce the total key count, I might be able to add another layer in the future, but for now three layers are enough.

###Characteristics

• A general layout that does not deviate much from QWERTY
• The following keys are on the thumbs:
  • Ctrl
  • Backspace
  • Cmd
  • Enter
  • Space
• No automatic mouse layer
• Right-hand trackball
• No function keys

Let's get into it.

###Layer 0

Layer 0 is the base layout. Most keys match QWERTY. I configure the keymap by editing source code (not using Remap), so I cannot share images.

1
[0] = LAYOUT_universal(
2
  KC_ESC   , KC_Q     , KC_W     , KC_E     , KC_R     , KC_T     ,                                        KC_Y     , KC_U     , KC_I     , KC_O     , KC_P     , KC_MINS  ,
3
  KC_TAB   , KC_A     , KC_S     , KC_D     , KC_F     , KC_G     ,                                        KC_H     , KC_J     , KC_K     , KC_L     , KC_SCLN  , KC_QUOT  ,
4
  KC_LSFT  , KC_Z     , KC_X     , KC_C     , KC_V     , KC_B     ,                                        KC_N     , KC_M     , KC_COMM  , KC_DOT   , KC_SLSH  , KC_LALT  ,
5
                        KC_NO    , MO(1)    , KC_BSPC  , KC_LCTL  , KC_LGUI,                    KC_ENT   , KC_SPC   , KC_NO    ,            _______  , MO(2)
6
),

Key points:

• The leftmost column follows the common order: ESC, TAB, Shift
  • I do not use CAPS LOCK, so it is not assigned
• Left thumb keys (right to left): Cmd, Ctrl, Backspace
• A key to switch to Layer 1 sits to the left of those three thumb keys
• Right thumb keys (left to right): Enter, Space
• The key to the right of the trackball switches to Layer 2
• Alt is placed where right shift normally is

Numbers, `, [, ], =, \ are assigned to Layer 1 below.

####Thumbs

Thumbs are where personal preference shows. This layout works well for me. I use Emacs often, so assigning Ctrl to the thumb solves the Emacs pinky problem.

(Even without a split keyboard that supports thumb keys, I assign Ctrl to Caps Lock (above left shift), so the pinky load is not that high anyway.)

I always use this layout for the three left-thumb keys and two right-thumb keys, but I change the surrounding thumb keys depending on the keyboard. For example, on keyboards like Corne V4 Cherry or Corne Cherry V3 that allow three right-thumb keys, I assign MO(1) (which is on the left thumb here) to the third right-thumb key (the position where the Keyball's ball is). On the Keyball66, I assign Alt to MO(1) and keep right shift as shift. I have gotten used to having shift only on the left hand, so I might adjust the Keyball66 layout too.

####Escape

On the Keyball44 I put ESC in the top left. I do the same on the Corne Cherry V3. It feels like home.

However, on my daily Keyball66 I put ESC in the bottom left and press it with my palm. Some people press Ctrl with the palm on a standard JIS layout, and I do the same for ESC. When I use Vim, I prefer Ctrl-[ instead of ESC, so ESC isn't used that much. This layout is enough for me.

####Fifth left-thumb key

The fifth key from the right on the left thumb (left of MO(1)) is disabled. This position is hard for me to use on any keyboard. Bending the thumb inward that far or trying to press it with the ring finger just never worked for me. And I can assign all the keys I need without it, so I have no motivation to use it.

###Layer 1

Layer 2 supplements Layer 1. With 44 keys, you cannot fit numbers and some symbols into a single layer. So the overflow goes into Layer 1. Layer 1 is active only while holding the MO(1) key on the left thumb of Layer 0.

1
[1] = LAYOUT_universal(
2
  KC_GRAVE , KC_1     , KC_2     , KC_3    , KC_4     , KC_5     ,                                         KC_6     , KC_7     , KC_8     , KC_9     , KC_0     , KC_EQUAL ,
3
  _______  , KC_NO    , KC_NO    , KC_NO   , KC_NO    , KC_NO    ,                                         KC_NO    , KC_NO    , KC_NO    , KC_NO    , KC_NO    , KC_BSLS  ,
4
  _______  , _______  , KC_NO    , KC_NO   , KC_NO    , KC_LBRC  ,                                         KC_RBRC  , KC_NO    , KC_NO    , KC_NO    , KC_NO    , _______  ,
5
                        _______  , _______ , _______  , _______  , _______  ,                   _______  , _______  , _______  ,            _______  , _______
6
),

Many people place symbols that normally require Shift in the empty spaces under or beside the number row. I do not like layouts that deviate far from QWERTY, so I keep the number row in the usual order on the next row down. I assign [ and ] to the positions of b and n. This seems fairly common on low-key keyboards like the Keyball44.

I also place `, =, and \ close to their QWERTY positions, which reduces the burden of memorizing key locations (except for [ and ]).

###Layer 3

Layer 3 is for mouse operations, cursor keys, and window operations. It is active only while holding the key to the right of the trackball on Layer 0. I press that key with the base of my pinky while operating the trackball, which naturally switches layers during mouse use.

The window bindings match macOS Spectacle. Since Spectacle is no longer maintained, I use Rectangle with the same keybinds.

1
[2] = LAYOUT_universal(
2
  _______  , KC_NO         , LCTL(KC_UP)  , LAG(KC_F) , LCTL(KC_DOWN) , KC_NO         ,                                         KC_NO   , KC_BTN1  , KC_UP   , KC_BTN2  , KC_NO   , SCRL_MO ,
3
  _______  , LCTL(KC_LEFT) , LAG(KC_LEFT) , KC_NO     , LAG(KC_RGHT)  , LCTL(KC_RGHT) ,                                         KC_NO   , KC_LEFT  , KC_DOWN , KC_RGHT  , KC_NO   , KC_NO   ,
4
  _______  , KC_NO         , KC_NO        , LAG(KC_C) , KC_NO         , KC_NO         ,                                         KC_NO   , KC_NO    , KC_NO   , KC_NO    , KC_NO   , _______ ,
5
                             _______      , _______   ,  _______      , _______       , _______  ,                   _______  , _______ , _______            , _______  , _______
6
  ),

Left hand for window control, right hand for mouse and cursor.

####Left-hand controls

The left-hand bindings are macOS-specific. I mapped window maximize, left, and right to e, s, and f, like WASD. Pressing c centers the window, which is useful when I want three windows on an ultrawide display.

macOS has workspaces, and I mapped switching left/right to a and g. The default is Ctrl-Left and Ctrl-Right, so you can use it without extra keys, but it requires three keys at once. For frequent use I prefer easier keypresses, so I chose a and g as intuitive positions.

I mapped Mission Control and App Expose to w and r, respectively.

I use these keys for window and workspace control. There are still unused keys, so I could map more window actions or Raycast. As with Emacs bindings, if I add too many at once, I end up forgetting them. Now that these bindings are familiar, it may be time to add more.

####Right-hand controls

Right-hand controls are simple.

I mapped left click and right click to u and o. I set scroll mode on -. While holding -, the trackball scrolls vertically, and with Shift held it scrolls horizontally. That is the mouse setup. Scrolling is a bit special, but the click buttons are placed where the hand naturally rests when using the ball, so it should feel natural to most people.

Cursor keys are mapped to i, j, k, l for up, left, down, right. Some people might prefer Vim bindings.

##Future plans

I forgot that I bought the Keyball44 in order to buy a Keyballish. I still want a Keyballish, but an unexpected expense came up, so unless I make money in stocks, it probably has to wait until around the end of next year...