zmk/readme.md
2022-12-29 15:49:26 -05:00

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# 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 an Advantage 360 pro.
## Key features
- clean keymap + unicode setup using helper macros from
[zmk-nodefree-config](https://github.com/urob/zmk-nodefree-config)
- modified Github Actions workflow that recognizes git-submodules
- 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) on the base layer; sticky mods on
other layers
- num-word: a zmk version of smart-layers that automatically de-activate for non-numbers
- combos replacing the symbol layer
- arrow-cluster doubles as home/end/etc on long-press,
bspc/del delete words on long-press
- sticky shift on right thumb, double-tap (or shift + tap)[^1] activates caps-word
- <kbd>shift</kbd> + <kbd>,</kbd> morphs into <kbd>;</kbd> and <kbd>shift</kbd> +
<kbd>.</kbd> morphs into <kbd>;</kbd> (freeing up the right pinky for
<kbd>repeat</kbd>)
- <kbd>shift</kbd> + <kbd>ctrl</kbd> +
<kbd>,</kbd> morphs into <kbd><</kbd> and <kbd>shift</kbd> + <kbd>ctrl</kbd> +
<kbd>.</kbd> morphs into <kbd>></kbd>
- <kbd>shift</kbd> + <kbd>space</kbd> morphs into <kbd>dot</kbd><kbd>space</kbd>
<kbd>sticky-shift</kbd>
- "Greek" layer for mathematical typesetting (activated via sticky-layer combo)
![](img/keymap.png)
## Timeless homerow mods
Homerow mods [are great](https://precondition.github.io/home-row-mods). But they can
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 "timeless" HRM
setup.[^2]
Here's what I have ended up with: A "timeless" HRM setup with virtually no misfires and
yet 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 "timeless". But it also creates two
problems: (1) In order to get a "mod" we now have to hold the HRM keys for
what feels like eternity. (2) In normal typing, when tapping keys, there can be
long delays between the press of a key and the time it appears on the screen. Enter my
two favorite configuration options:
* 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 `global-quick-tap` property, which
immediately resolves a HRM as "tap" when it is pressed shortly *after* another key
has been tapped.[^3] This all but completely eliminates the delay when typing.
This is almost perfect, but there's 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. Given the `balanced` flavor,
this would falsely register `key 1` as a mod. To prevent this, 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. The official ZMK version for positional-hold-taps 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 a small
patch that delays the positional-hold-tap decision until the next key's *release* ([PR
#1423](https://github.com/zmkfirmware/zmk/pull/1423)). With the patch, multiple mods
can be combined when held, while I still get the benefit from positional-hold-taps
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`.
Here's my configuration (I use a bunch of [helper
macros](https://github.com/urob/zmk-nodefree-config) to simplify the syntax, but they
are not necessary):
```C++
/* use helper macros to define left and right hand keys */
#include "../zmk-nodefree-config/keypos_def/keypos_36keys.h" // keyposition helpers
#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_BEHAVIOR(hml, hold_tap,
flavor = "balanced";
tapping-term-ms = <280>;
quick-tap-ms = <175>; // repeat on tap-into-hold
global-quick-tap-ms = <150>; // requires PR #1387
bindings = <&kp>, <&kp>;
hold-trigger-key-positions = <KEYS_R THUMBS>;
hold-trigger-on-release; // requires PR #1423
)
/* right-hand HRMs */
ZMK_BEHAVIOR(hmr, hold_tap,
flavor = "balanced";
tapping-term-ms = <280>;
quick-tap-ms = <175>; // repeat on tap-into-hold
global-quick-tap-ms = <150>; // requires PR #1387
bindings = <&kp>, <&kp>;
hold-trigger-key-positions = <KEYS_L THUMBS>;
hold-trigger-on-release; // requires PR #1423
)
```
One last note, the configuration above uses some syntactic sugar introduced in [PR
#1387](https://github.com/zmkfirmware/zmk/pull/1387), which decouples the
`quick-tap-ms` timeout from the `global-quick-tap-ms` timeout. Without the PR, one
can replace `global-quick-tap-ms = <150>` with `global-quick-tap` for a
similar effect (`global-quick-tap` will use the regular `quick-tap-ms` timeout in this
case).
My personal [ZMK fork](https://github.com/urob/zmk) includes both the
global-quick-tap-ms PR and the hold-trigger-on-release PR (along with a few other PRs).
If you are looking for a ZMK-centric introduction to maintaining your own fork with a
custom selection of PRs, you might find my ["cookbook
approach"](https://gist.github.com/urob/68a1e206b2356a01b876ed02d3f542c7) helpful.
## Combo setup
I make heavy use of combos to replace the usual symbol layer. The combo layout aims to
put the most used symbols in easy-to-access locations and also make 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 aims for symmetry with the top row (subscript `_` aligns
with superscript `^`; minus `-` aligns with `+`; division `/` aligns with
multiplication `*`; logical-or `|` aligns with logical-and `&`)
- parenthesis, braces, brackets, `!` and `?` are set up symmetrically in prime locations
- numlock (on `W + P`), cut (on `X + D`), copy, and paste are on the left side for
one-handed mouse use
- `L + Y` activates Greek layer for next key, `L + U + Y` activates shifted Greek layer
for next key
## Experimental changes
- I recently reduced my core layout to 34 keys. Backspace, Delete and Tap are now all on
my Navigation-layer. To make room for these keys, I have added hold-taps to the arrow
cluster, which now double as Home/End and Beginning/End of document. I really like the
new navigation cluster and will likely keep it in one way or another
- 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 my Num-key (holding the key will activate the num layer as usual without
triggering Numword). Similar to Capsword, Numword continues to be activated as long
as I type numbers, and deactivates automatically on any other keypress. I found that
I use Numword for most of my numbers typing. For single digits, it effectively is a
sticky-layer, but importantly I can also use it for multiple digits. The only case
where it doesn't deactivate automatically is where immediately after a digit I would
type any of the letters on which my numpad is located (WFPRSTXCD), which is rare,
but does happen. For these cases I have a CANCEL key on my Nav layer that cancels
both Numword and Capsword.
- Since the switch to 34 keys, I freed up the tap-position on my left-most thumb key.
For now I added a secondary Bspc, but I am still searching for a better use. (I tried
adding Repeat here but I found that it doesn't work well adjacent to space)
## 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 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)). Workaround: pause
briefly when chording multiple HRMs together on positions that otherwise would trigger
a combo.
- `&bootloader` doesn't work with Planck_rev6
([#1086](https://github.com/zmkfirmware/zmk/issues/1086)). Workaround: Manually press
reset-button.
- "sticky-hold" swallows OS shift when typing quickly. Workaround: use sticky-tap for now.
- Sleep is not yet implemented ([#1077](https://github.com/zmkfirmware/zmk/issues/1077)).
Workaround: use sleep-macro instead.
- Invalid DFU suffix signature warning when flashing with dfu-util. No problem for now
but may cause issues with future versions of dfu-util.
[^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.
[^2]: I call it "timeless", because the large tapping-term makes the behavior
insensitive to the precise timings. One may say that there is still the
`global-quick-tap` timeout. However, with both a large tapping-term and
positional-hold-taps, the behavior is *not* actually sensitive to the
`global-quick-tap` timing: All it does is reduce the delay in typing; i.e., variations
in typing speed won't affect *what* is being typed but merly *how fast* it appears on
the screen.
[^3]: One potential downside of `global-quick-tap` is that it prevents using modifiers
*immediately* after another key press. Arguably, this is only problematic for shift,
which is not a problem for me, because I have a dedicated "sticky shift" on my right
thumb. If you rely on homerow mods for regular capitalization, you may want to reduce
the `global-quick-tap` term for just the two shift-mods to about 75-100ms.