# 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 - shift + , morphs into ; and shift + . morphs into ; (freeing up the right pinky for repeat) - shift + ctrl + , morphs into < and shift + ctrl + . morphs into > - shift + space morphs into dotspacesticky-shift - "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 = ; 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 = ; 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.