This is my personal ZMK firmware configuration build upon excellent config from urob. It consists of a 42-keys base layout used on my Corneish-Zen and Kinesis Advantage 360 Pro layout.

• "Timeless" homerow mods
• Magic thumb quadrupling as Sticky-shift/Capsword/Shift
• Arrow-cluster doubles as home, end, begin/end of document on long-press
• Simpler Devicetree syntax using helper macros from zmk-helpers
• Fully automated, nix-powered local build environment

1. Install the nix package manager:

   # Install Nix with flake support enabled
   curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix |
      sh -s -- install --no-confirm
   
   # Start the nix daemon without restarting the shell
   . /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh

2. Install direnv (and optionally but recommended nix-direnv¹) using your package manager of choice. E.g., using the nix package manager that we just installed²:

   nix profile install nixpkgs#direnv nixpkgs#nix-direnv
   

3. Set up the direnv shell-hook for your shell. E.g., for bash:

   # Install the shell-hook
   echo 'eval "$(direnv hook bash)"' >> ~/.bashrc
   
   # Enable nix-direnv (if installed in the previous step)
   mkdir -p ~/.config/direnv
   echo 'source $HOME/.nix-profile/share/nix-direnv/direnvrc' >> ~/.config/direnv/direnvrc
   
   # Optional: make direnv less verbose
   echo '[global]\nwarn_timeout = "2m"\nhide_env_diff = true' >> ~/.config/direnv/direnv.toml
   
   # Source the bashrc to activate the hook (or start a new shell)
   source ~/.bashrc

1. Clone your fork of this repository. I like to name my local clone zmk-workspace as it will be the toplevel of the development environment.

   # Replace `urob` with your username
   git clone https://github.com/urob/zmk-config zmk-workspace

2. Enter the workspace and set up the environment.

   # The first time you enter the workspace, you will be prompted to allow direnv
   cd zmk-workspace
   
   # Allow direnv for the workspace, which will set up the environment (this takes a while)
   direnv allow
   
   # Initialize the Zephyr workspace and pull in the ZMK dependencies
   # (same as `west init -l config && west update && west zephyr-export`)
   just init

After following the steps above your workspace should look like this:

zmk-workspace
├── config
├── firmware (created after building)
├── modules
├── zephyr
└── zmk

To build the firmware, simply type just build all from anywhere in the workspace. This will parse build.yaml and build the firmware for all board and shield combinations listed there.

To only build the firmware for a specific target, use just build <target>. This will build the firmware for all matching board and shield combinations. For instance, to build the firmware for my Corneish Zen, I can type just build zen, which builds both corneish_zen_v2_left and corneish_zen_v2_right. (just list shows all valid build targets.)

Additional arguments to just build are passed on to west. For instance, a pristine build can be triggered with just build all -p.

(For this particular example, there is also a just clean recipe, which clears the build cache. To list all available recipes, type just. Bonus tip: just provides completion scripts for many shells.)

The build environment packages keymap-drawer. just draw <keyboard> <keymap> parses relevant keymap for a given keyboard and draws it to draw/keymap.svg. For my two keyboards that is just draw adv360 adv360 and just draw corne_rotated corne.

To make changes to the ZMK source or any of the modules, simply edit the files or use git to pull in changes.

To switch to any remote branches or tags, use git fetch inside a module directory to make the remote refs locally available. Then switch to the desired branch with git checkout <branch> as usual. You may also want to register additional remotes to work with or consider making them the default in config/west.yml.

To update the ZMK dependencies, use just update. This will pull in the latest version of ZMK and all modules specified in config/west.yml. Make sure to commit and push all local changes you have made to ZMK and the modules before running this command, as this will overwrite them.

To upgrade the Zephyr SDK and Python build dependencies, use just upgrade-sdk. (Use with care -- Running this will upgrade all Nix packages and may end up breaking the build environment. When in doubt, I recommend keeping the environment pinned to flake.lock, which is continuously tested on all systems.)

Using the same Nix-based environment, I have set up a drop-in replacement for the default ZMK Github Actions build workflow. While mainly a proof-of-concept, it does run moderately faster, especially with a cold cache.

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), 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 changing active mods).
• Very minor: &bootloader doesn't work with stm32 boards like the Planck (#1086)

• The collection of ZMK modules used in this configuration.
• A ZMK-centric introduction to Git (useful for maintaining your own ZMK fork with a custom selection of PRs).