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https://github.com/urob/zmk-config

Personal ZMK firmware configuration for various boards (34-keys, Corneish Zen, Planck)
https://github.com/urob/zmk-config

corneish-zen planck zmk zmk-config

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Personal ZMK firmware configuration for various boards (34-keys, Corneish Zen, Planck)

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README 

        
# urob's zmk-config



This is my personal [ZMK firmware](https://github.com/zmkfirmware/zmk/)

configuration. It consists of a 34-keys base layout that is re-used for various

boards, including my Corneish Zen and my Planck.



This branch is updated for the latest ZMK using Zephyr 3.5. A legacy version

compatible with Zephyr 3.0 is available

[here](https://github.com/urob/zmk-config/tree/main-zephyr-3.0).



## Highlights



- clean keymap + unicode setup using helper macros from

  [zmk-helpers](https://github.com/urob/zmk-helpers)

- the base keymap and combo setup are independent of the physical location of

  keys and are re-used for multiple keyboards. The configuration is fit onto

  larger boards by padding it via a modular structure of "extra keys"

- ["timeless" homerow mods](#timeless-homerow-mods)

- combos replacing the symbol layer

- smart numbers and smart mouse layers that automatically toggle off when done

- sticky shift on right thumb, double-tap (or shift + tap)[^1] activates

  caps-word

- arrow-cluster doubles as home, end, begin/end of

  document on long-press

- more intuitive shift-actions: , ;, . : and ?

  !

- shift + space morphs into dot →

  space → sticky-shift

- "Greek" layer for mathematical typesetting (activated as sticky-layer via a

  combo)

- modified Github Actions workflow that recognizes git-submodules

- automated

  [build-scripts](https://github.com/urob/zmk-config/tree/main/scripts#readme)

  for local and Docker-based building (independently of VS Code)



![](img/keymap.png)



## Timeless homerow mods



[Homerow mods](https://precondition.github.io/home-row-mods) (aka "HRMs") can be

a game changer -- at least in theory. In practice, they require some finicky

timing: In its most naive implementation, in order to produce a "mod", they must

be held _longer_ than `tapping-term-ms`. In order to produce a "tap", they must

be held _less_ than `tapping-term-ms`. This requires very consistent typing

speeds that, alas, I do not possess. Hence my quest for a "timer-less" HRM

setup.[^2]



After months of tweaking, I eventually ended up with a HRM setup that is

essentially timer-less, resulting in virtually no misfires. Yet it provides a

fluent typing experience with mostly no delays.



Let's suppose for a moment we set `tapping-term-ms` to something ridiculously

large, say 5 seconds. This makes the configuration timer-less of sorts. But it

has two problems: (1) To activate a mod we will have to hold the HRM keys for

what feels like eternity. (2) During regular typing, there are delays between

the press of a key and the time it appears on the screen.[^3] Enter two my

favorite ZMK features:



- To address the first problem, I use ZMK's `balanced` flavor, which produces a

  "hold" if another key is both pressed and released within the tapping-term.

  Because that is exactly what I normally do with HRMs, there is virtually never

  a need to wait past my long tapping term (see below for two exceptions).

- To address the typing delay, I use ZMK's `require-prior-idle-ms` property,

  which immediately resolves a HRM as "tap" when it is pressed shortly _after_

  another key has been tapped. This all but completely eliminates the delay.



This is great but there are still a few rough edges:



- When rolling keys, I sometimes unintentionally end up with "nested" key

  sequences: `key 1` down, `key 2` down and up, `key 1` up. Because of the

  `balanced` flavor, this would falsely register `key 1` as a mod. As a remedy,

  I use ZMK's `positional hold-tap` feature to force HRMs to always resolve as

  "tap" when the _next_ key is on the same side of the keyboard. Problem solved.

- ... or at least almost. By default, positional-hold-tap performs the

  positional check when the next key is _pressed_. This is not ideal, because it

  prevents combining multiple modifiers on the same hand. To fix this, I use the

  `hold-trigger-on-release` setting, which delays the positional-hold-tap

  decision until the next key's _release_. With the setting, multiple mods can

  be combined when held, while I still get the benefit from positional-hold-tap

  when keys are tapped.

- So far, nothing of the configuration depends on the duration of

  `tapping-term-ms`. In practice, there are two reasons why I don't set it to

  infinity:

  1. Sometimes, in rare circumstances, I want to combine a mod with a alpha-key

     _on the same hand_ (e.g., when using the mouse with the other hand). My

     positional hold-tap configuration prevents this _within_ the tapping term.

     By setting the tapping term to something large but not crazy large (I use

     280ms), I can still use same-hand `mod` + `alpha` shortcuts by holding the

     mod for just a little while before tapping the alpha-key.

  2. Sometimes, I want to press a modifier without another key (e.g., on

     Windows, tapping `Win` opens the search menu). Because the `balanced`

     flavour only kicks in when another key is pressed, this also requires

     waiting past `tapping-term-ms`.

- Finally, it is worth noting that this setup works best in combination with a

  dedicated shift for capitalization during normal typing (I like sticky-shift

  on a home-thumb). This is because shifting alphas is the one scenario where

  pressing a mod may conflict with `require-prior-idle-ms`, which may result in

  false negatives when typing fast.



Here's my configuration (I use a bunch of

[helper macros](https://github.com/urob/zmk-helpers) to simplify the

syntax, but they are not necessary):



```C++

/* use helper macros to define left and right hand keys */

#include "zmk-helpers/key-labels/36.h"                                      // key-position labels

#define KEYS_L LT0 LT1 LT2 LT3 LT4 LM0 LM1 LM2 LM3 LM4 LB0 LB1 LB2 LB3 LB4  // left-hand keys

#define KEYS_R RT0 RT1 RT2 RT3 RT4 RM0 RM1 RM2 RM3 RM4 RB0 RB1 RB2 RB3 RB4  // right-hand keys

#define THUMBS LH2 LH1 LH0 RH0 RH1 RH2                                      // thumb keys



/* left-hand HRMs */

ZMK_HOLD_TAP(hml,

    flavor = "balanced";

    tapping-term-ms = <280>;

    quick-tap-ms = <175>;                // repeat on tap-into-hold

    require-prior-idle-ms = <150>;

    bindings = <&kp>, <&kp>;

    hold-trigger-key-positions = ;

    hold-trigger-on-release;             // delay positional check until key-release

)



/* right-hand HRMs */

ZMK_HOLD_TAP(hmr,

    flavor = "balanced";

    tapping-term-ms = <280>;

    quick-tap-ms = <175>;                // repeat on tap-into-hold

    require-prior-idle-ms = <150>;

    bindings = <&kp>, <&kp>;

    hold-trigger-key-positions = ;

    hold-trigger-on-release;             // delay positional check until key-release

)

```



### Required firmware



After a recent round of patches, the above configuration now works with upstream

ZMK.



Other parts of my configuration still require a few PRs that aren't yet in

upstream ZMK. My personal [ZMK fork](https://github.com/urob/zmk) includes all

PRs needed to compile my configuration. If you prefer to maintain your own fork

with a custom selection of PRs, you might find this

[ZMK-centric introduction to Git](https://gist.github.com/urob/68a1e206b2356a01b876ed02d3f542c7)

helpful.



### Troubleshooting



Hopefully, the above configuration "just works". If it doesn't, here's a few

smaller (and larger) things to try.



- **Noticeable delay when tapping HRMs:** Increase `require-prior-idle-ms`. As a

  rule of thumb, you want to set it to at least `10500/x` where `x` is your

  (relaxed) WPM for English prose.[^4]

- **False negatives (same-hand):** Reduce `tapping-term-ms` (or disable

  `hold-trigger-key-positions`)

- **False negatives (cross-hand):** Reduce `require-prior-idle-ms` (or set

  flavor to `hold-preferred` -- to continue using `hold-trigger-on-release`, you

  must also

  [patch ZMK](https://github.com/celejewski/zmk/commit/d7a8482712d87963e59b74238667346221199293)

  or use [an already patched branch](https://github.com/urob/zmk))

- **False positives (same-hand):** Increase `tapping-term-ms`

- **False positives (cross-hand):** Increase `require-prior-idle-ms` (or set

  flavor to `tap-preferred`, which requires holding HRMs past tapping term to

  activate)



## Using combos instead of a symbol layer



I am a big fan of combos for all sort of things. In terms of comfort, I much

prefer them over accessing layers that involve lateral thumb movements to be

activated, especially when switching between different layers in rapid

succession.



One common concern about overloading the layout with combos is that they lead to

misfires. Fortunately, the above-mentioned `require-prior-idle-ms` option also

works for combos, which in my experience all but completely eliminates the

problem -- even when rolling keys on the home row!



My combo layout aims to place the most used symbols in easy-to-access locations

while also making them easy to remember. Specifically:



- the top vertical-combo row matches the symbols on a standard numbers row

  (except `+` and `&` being swapped)

- the bottom vertical-combo row is symmetric to the top row (subscript `_`

  aligns with superscript `^`; minus `-` aligns with `+`; division `/` aligns

  with multiplication `*`; logical-or `|` aligns with logical-and `&`)

- parenthesis, braces, brackets are set up symmetrically as horizontal combos

  with `<`, `>`, `{` and `}` being accessed from the Navigation layer (or when

  combined with `Shift`)

- left-hand side combos for `tap`, `esc`, `enter`, `cut` (on X +

  D), `copy` and `paste` that go well with right-handed mouse usage

- L + Y switches to the Greek layer for a single key

  press, L + U + Y activates one-shot shift in

  addition

- W + P activates the smart mouse layer



## Smart layers and other gimmicks



##### Numword



Inspired by Jonas Hietala's

[Numword](https://www.jonashietala.se/blog/2021/06/03/the-t-34-keyboard-layout/#where-are-the-digits)

for QMK, I implemented my own version of

[Smart-layers for ZMK](https://github.com/zmkfirmware/zmk/pull/1451). It is

triggered via a single tap on "Smart-Num". Numword continues to be activated as

long as I type numbers, and deactivates automatically on any other keypress

(holding it activates a non-sticky num layer).



After using Numword for more than a year now, I have been overall very happy

with it. When typing single digits, it effectively is a sticky-layer but with

the added advantage that I can also use it to type multiple digits.



The main downside is that if a sequence of numbers is _immediately_ followed by

any of the letters on which my numpad is located (WFPRSTXCD), then the automatic

deactivation won't work. But this is rare -- most number sequences are

terminated by `space`, `return` or some form of punctuation/delimination. To

deal with the rare cases where they aren't, there is a `CANCEL` key on the

navigation-layer that deactivates Numword, Capsword and Smart-mouse. (It also

toggles off when pressing `Numword` again, but I find it cognitively easier to

have a dedicated "off-switch" than keeping track of which modes are currently

active.)



##### Smart-Mouse



Similarly to Numword, I have a smart-mouse layer (activated by comboing

W + P), which replaces the navigation cluster with scroll

and mouse-movements, and replaces the right thumbs with mouse buttons. Pressing

any other key automatically deactivates the layer.



##### Capsword



My right thumb triggers three variations of shift: Tapping yields sticky-shift

(used to capitalize alphas), holding activates a regular shift, and

double-tapping (or equivalently shift + tap) activates ZMK's Caps-word behavior.



One minor technical detail: While it would be possible to implement the

double-tap functionality as a tap-dance, this would add a delay when using

single taps. To avoid the delays, I instead implemented the double-tap

functionality as a mod-morph.



##### Multi-purpose Navigation cluster



To economize on keys, I am using hold-taps on my navigation cluster, which yield

`home`, `end`, `begin/end of document`, and `delete word forward/backward` on

long-presses. The exact implementation is tweaked so that `Ctrl` is silently

absorbed in combination with `home` and `end` to avoid accidental document-wide

operations (which are accessible via the dedicated `begin/end document keys`.)



##### Swapper



I am using [Nick Conway](https://github.com/nickconway)'s fantastic

[tri-state](https://github.com/zmkfirmware/zmk/pull/1366) behavior for a

one-handed Alt-Tab switcher (`PWin` and `NWin`).



##### Repeat



I recently switched to 25g-chocs on one of my keyboards. I already was very

happy with my combos prior to that (even with heavy-ish MX-switches). But with

the light chocs, I find that I can now even use them for regular typing. While I

haven't yet tried placing alphas on combos, I am currently experimenting with a

`repeat` combo on my home row that I use to reduce SFUs when typing

double-letter words.



## Issues and workarounds



Since I switched from QMK to ZMK I have been very impressed with how easy it is

to set up relatively complex layouts in ZMK. For the most parts I don't miss any

functionality (to the contrary, I found that ZMK supports many features natively

that would require complex user-space implementations in QMK). Below are a few

remaining issues:



- ZMK does not yet support "tap-only" combos

  ([#544](https://github.com/zmkfirmware/zmk/issues/544)), requiring a brief

  pause when wanting to chord HRMs that overlap with combo positions. As a

  workaround, I implemented all homerow combos as homerow-mod-combos. This is

  good enough for day-to-day, but does not address all edge cases (eg

  dynamically adding/removing mods doesn't work well). Having a native solution

  akin to QMK's "COMBO_MUST_TAP" property would be fantastic.

- Another item on my wishlist are adaptive keys

  ([#1624](https://github.com/zmkfirmware/zmk/issues/1624)). This would open the

  door for things like spacespace becoming

  .spacesticky-shift. (Using tap-dance isn't

  really an option here due to the delay it adds)

- A minor thing is that ZMK doesn't yet support any keys on the

  desktop-user-page; e.g., OS sleep

  ([#1077](https://github.com/zmkfirmware/zmk/issues/1077),

  [#1535](https://github.com/zmkfirmware/zmk/issues/1535))

- Very minor: `&bootloader` doesn't work with stm32 boards like the Planck

  ([#1086](https://github.com/zmkfirmware/zmk/issues/1086))



[^1]:

    Really what's happening is that `Shift` + my right home-thumb morph into

    caps-word. This gives me two separate ways of activating it: (1) Holding the

    homerow-mod shift on my left index-finger and then pressing my right

    home-thumb, which is my new preferred way. Or, (2) double-tapping the right

    home-thumb, which also works because the first tap yields sticky-shift,

    activating the mod-morph upon the second tap. But even when only activating

    via double-tapping, this implementation is advantageous compared to using

    tap-dance as it does not create any delay when single-tapping the key.



[^2]:

    I call it "timer-less", because the large tapping-term makes the behavior

    insensitive to the precise timings. One may say that there is still the

    `require-prior-idle` timeout. However, with both a large tapping-term and

    positional-hold-taps, the behavior is _not_ actually sensitive to the

    `require-prior-idle` timing: All it does is reduce the delay in typing;

    i.e., variations in typing speed won't affect _what_ is being typed but

    merely _how fast_ it appears on the screen.



[^3]:

    The delay is determined by how quickly a key is released and is not directly

    related to the tapping-term. But regardless of its length, most people still

    find it noticable and disruptive.



[^4]:

    E.g, if your WPM is 70 or larger, then the default of 150ms (=10500/70)

    should work well. The rule of thumb is based on an average character length

    of 4.7 for English words. Taking into account 1 extra tap for `space`, this

    yields a minimum `require-prior-idle-ms` of (60 _ 1000) / (5.7 _ x) ≈ 10500

    / x milliseconds. The approximation errs on the safe side, as in practice

    home row taps tend to be faster than average.