{"id":6252,"date":"2026-06-09T13:12:53","date_gmt":"2026-06-09T12:12:53","guid":{"rendered":"https:\/\/pmortensen.eu\/world2\/?p=6252"},"modified":"2026-06-22T14:35:42","modified_gmt":"2026-06-22T13:35:42","slug":"hello-world-for-zmk-the-latest-version","status":"publish","type":"post","link":"https:\/\/pmortensen.eu\/world2\/2026\/06\/09\/hello-world-for-zmk-the-latest-version\/","title":{"rendered":"Hello, World! for ZMK, the latest version"},"content":{"rendered":"

<\/p>\n

The short version: After setting up ZMK<\/a>, for example, with the completely linear<\/em> pastable command lines provided below, use “west build -b planck\/\/zmk<\/em><\/strong>” instead of “west build -b planck_rev6<\/em><\/strong>” to build the sample keyboard firmware (to test that building actually works). The official documentation is out of date.<\/p>\n

Introduction<\/h2>\n

Presuming the build environment is set up for building ZMK keyboard firmware (see below for complete instructions for a non-Docker<\/a> and non-GitHub Actions<\/a> approach), the step in the official documentation<\/a> for building the firmware for a sample keyboard is:<\/p>\n

\r\nwest build -b planck_rev6\r\n<\/pre>\n
Or if repeating (for example, after trying building keyboard firmware for some other keyboard, probably due to CMake<\/a>isms; ‘-p’ is an alias of –pristine<\/a> (two ASCII dashes, not as rendered here). See also Pristine Building<\/em><\/a>):<\/p>\n
\r\nwest build -p -b planck_rev6\r\n<\/pre>\n
It is also in a previous blog post, Customising the ZMK-based Keychron B6 Pro keyboard without the Via clone<\/em><\/a>. And it worked at that time<\/em><\/strong>, with the current version of the main ZMK project at that time (about 2025-03-10).<\/p>\n
But this results in a build error (only the essential part is shown here; see Appendix A<\/a> for the full transcript, including the full error message):<\/p>\n
\r\nInvalid BOARD;\r\n<\/pre>\n
Realising “planck_rev6” has been both moved and renamed, from \/app\/boards\/arm\/planck<\/em> to \/app\/boards\/olkb\/planck<\/em> (the official documentation is clearly out of date), the build command would seem to be:<\/p>\n
\r\nwest build -p -b planck\r\n<\/pre>\n
It does get further, but it also fails (only the essential part is shown here; see Appendix A<\/a> for the full transcript, including the full error message):<\/p>\n
\r\n#error "NUM_IRQ_PRIO_BITS and __NVIC_PRIO_BITS are not set to the same value"\r\n<\/pre>\n
See Appendix A<\/a> for the full error output.<\/p>\n
The solution<\/h2>\n
The correct command line for building the sample keyboard is:<\/p>\n
\r\nwest build -p -b planck\/\/zmk\r\n<\/pre>\n
This is impossible to guess, but it is hinted at in an official ZMK blog post:<\/p>\n
    \n
  1. Zephyr 4.1 Update<\/em><\/a> (2025-12-09)<\/li>\n<\/ol>\n
    Section Board Revisions<\/em> has:<\/p>\n
      \n
    1. “planck_rev6 -> planck\/\/zmk”<\/em><\/li>\n<\/ol>\n
      The “\/\/zmk” probably means something along the lines<\/a> of “variants” (whatever that is in this context). And<\/a> “…all board definitions found in the ZMK tree now must be used with a zmk<\/strong> variant”<\/em>. The empty content in “\/\/” seems to be some kind of shorthand (it could apparently be explicit<\/a> – “…only one SoC<\/a> on the board<\/a>“<\/em>).<\/p>\n
      Or maybe it is just a pure naming convention<\/a> used by the ZMK project?? That is, without any bearing on building the keyboard, meaning to Zephyr, etc., except using that exact string?<\/p>\n
      Result (slightly formatted):<\/p>\n
      \r\nMemory region   Used Size  Region Size  %age Used\r\n-------------------------------------------------\r\n       FLASH:     47624 B       256 KB     18.17%\r\n         RAM:     11736 B        40 KB     28.65%\r\n         CCM:        0 GB         8 KB      0.00%\r\n    IDT_LIST:        0 GB        32 KB      0.00%\r\n\r\nGenerating files from \/home\/embo\/main_ZMK\/app\/build\/zephyr\/zmk.elf\r\nfor board: planck\r\n<\/pre>\n
      And in the file system:<\/p>\n
      \r\n975388 Jun  4 05:33 \/home\/embo\/main_ZMK\/app\/build\/zephyr\/zephyr_pre0.elf\r\n974604 Jun  4 05:33 \/home\/embo\/main_ZMK\/app\/build\/zephyr\/zmk.elf\r\n<\/pre>\n
      Here is a transcript<\/a>.<\/p>\n
      Installing ZMK, using completely linear command lines<\/h2>\n
      Below are the (linear) command lines to set up the main ZMK project on a Debian<\/a>-like system (LMDE<\/a>, Linux Mint<\/a>, Ubuntu<\/a>, Debian itself, Lubuntu<\/a>, Kubuntu<\/a>, Xubuntu<\/a>, BunsenLabs<\/a>, Linux Lite<\/a>, WSL<\/a>, etc.), and compile the keyboard firmware for a sample keyboard.<\/p>\n
      It was (repeatedly) tested on LMDE 7<\/a> (Gigi) with ZMK version 26246D (2026-05-30), branch ‘main’. It took about 25 minutes on my system using a 4G<\/a> connection (LTE. On the order of 30 Mbit\/s).<\/p>\n
      Every step has a ‘cd’ (when required), so it can easily be resumed if something goes wrong (without having to think about what the current folder for that step is supposed to be). That is, it is independent of the current directory.<\/p>\n
      Warning<\/em><\/strong>: Note that with “–assume-yes” (“-y” = “–yes” = “–assume-yes”) for ‘sudo apt upgrade’ and ‘apt install’, the  upgrade and installation of the ZMK prerequisites becomes unconditional<\/em><\/strong> (so that pasting all the lines after “sudo ls > \/dev\/null” can become one single step). For a more cautious approach, remove the two “–assume-yes”s and upgrade and install the prerequisites as separate steps.<\/p>\n
      \r\n# Based on the official ZMK install instructions\r\n# (for "native" building):\r\n#\r\n#   <https:\/\/zmk.dev\/docs\/development\/local-toolchain\/setup\/native>\r\n#\r\n# Prime sudo. Though only required for\r\n# installing the dependencies, etc.\r\n#\r\nsudo ls > \/dev\/null\r\n\r\n# <https:\/\/docs.zephyrproject.org\/3.5.0\/develop\/getting_started\/index.html#select-and-update-os>\r\nsudo apt update\r\n\r\n# Note: This will upgrade packages which may be \r\n#       completely unrelated to the ZMK build,\r\n#       for example, package 'dotnet-sdk-10.0' \r\n#\r\nsudo apt-get --assume-yes upgrade \r\n\r\n# Install the required dependencies:\r\nsudo apt-get --assume-yes install --no-install-recommends \r\n  git cmake ninja-build gperf \\\r\n  ccache dfu-util device-tree-compiler wget \\\r\n  python3-dev python3-pip python3-setuptools python3-tk python3-wheel xz-utils file \\\r\n  make gcc gcc-multilib g++-multilib libsdl2-dev libmagic1\r\n\r\n\r\ncd $HOME\r\necho ; echo "Start cloning: $(date +%FT%T_%N_ns)" ; echo\r\ngit clone https:\/\/github.com\/zmkfirmware\/zmk.git  main_ZMK\r\necho ; echo "End cloning:   $(date +%FT%T_%N_ns)" ; echo\r\n\r\n\r\npython3 -m venv ~\/.main_ZMK_environment4\r\nsource ~\/.main_ZMK_environment4\/bin\/activate\r\n\r\n\r\ncd $HOME\/main_ZMK\r\ngit status   # Confirm Git branch "main"\r\n\r\n\r\n# Install 'west'\r\n    cd $HOME\/main_ZMK\r\n    pip install west\r\n\r\n\r\n# Initialise the application and update\r\n# to fetch modules, including Zephyr:\r\n    cd $HOME\/main_ZMK\r\n    echo ; echo "Start 'west init & update': $(date +%FT%T_%N_ns)" ; echo\r\n    west init -l app\/           # Current directory at the top of the\r\n                                # cloned repository is assumed\r\n    #cd $HOME\r\n    #west init $HOME\/main_ZMK  # Zephyr. Absolute. Without "\/app"\r\n    #cd $HOME\/main_ZMK\r\n\r\n    west update\r\n    echo ; echo "End 'west init& update':   $(date +%FT%T_%N_ns)" ; echo\r\n\r\n\r\n# Export a Zephyr CMake package. This allows CMake to\r\n# automatically load boilerplate code required for\r\n# building Zephyr applications.\r\ncd $HOME\/main_ZMK\r\nwest zephyr-export\r\n\r\n\r\ncd $HOME\/main_ZMK\r\nwest packages pip --install\r\n\r\n\r\n# It takes a lot of time!\r\n#\r\n# '\/zephyr' is critical...\r\n#\r\n# But on LMDE 6, it failed due to a\r\n# requirement of Python 3.12... It\r\n# apparently only has 3.11.2...\r\n#\r\n# LMDE 7: Python 3.13.5\r\n#\r\n# Starts by downloading the Zyphyr SDK v. 1.0.1\r\n# compressed tar ball (70 MB).\r\n#\r\n# And installs things like (downloading 45 - 145 MB\r\n# for each):\r\n#\r\n#   'arm-zephyr-eabi'    GNU toolchain.\r\n#   'riscv64-zephyr-elf' GNU toolchain.\r\n#\r\ncd $HOME\/main_ZMK\/zephyr\r\necho ; echo "Start 'west sdk install': $(date +%FT%T_%N_ns)" ; echo\r\nwest sdk install\r\necho ; echo "End 'west sdk install':   $(date +%FT%T_%N_ns)" ; echo\r\n\r\n# Exit the virtual Python environment\r\ndeactivate\r\n\r\n\r\n# #####################################\r\n#\r\n# Build\r\n#\r\n# Start state:\r\n#\r\n#   A new terminal window, thus activating the\r\n#   virtual Python environment is required\r\n#\r\n#   '-p' to erase the memory of a previous\r\n#   build, e.g, 'rtl87x2g_evb_a', if any\r\n#\r\nsource ~\/.main_ZMK_environment4\/bin\/activate\r\ncd $HOME\/main_ZMK\/app\r\n\r\n#   -- Zephyr version: 4.1.0 (\/home\/embo\/main_ZMK\/zephyr), build: 58a5874a446a\r\n#   [187\/187] Linking C executable zephyr\/zmk.elf\r\n#\r\n#   Memory region         Used Size  Region Size  %age Used\r\n#              FLASH:       47624 B       256 KB     18.17%\r\n#                RAM:       11736 B        40 KB     28.65%\r\n#                CCM:          0 GB         8 KB      0.00%\r\n#           IDT_LIST:          0 GB        32 KB      0.00%\r\n#   Generating files from \/home\/embo\/main_ZMK\/app\/build\/zephyr\/zmk.elf for board: planck\r\n#\r\necho ; echo "Start 'west build': $(date +%FT%T_%N_ns)" ; echo\r\nwest build -p -b planck\/\/zmk\r\necho ; echo "End 'west build':   $(date +%FT%T_%N_ns)" ; echo\r\n\r\nfind $HOME\/main_ZMK\/app | grep elf | xargs ls -l\r\n\r\n  # 975388 Jun  4 05:33 \/home\/embo\/main_ZMK\/app\/build\/zephyr\/zephyr_pre0.elf\r\n  # 974604 Jun  4 05:33 \/home\/embo\/main_ZMK\/app\/build\/zephyr\/zmk.elf\r\n\r\n\r\n# Exit the virtual Python environment\r\ndeactivate\r\n\r\n\r\n# Extra (is here, because it may or may not block\r\n#        with prompts, 'less' paging, etc.):\r\n# \r\n# Check ZMK version. For example, FF09F2 (2026-06-08)\r\ngit -C $HOME\/main_ZMK status # 'On branch main'\r\ngit -C $HOME\/main_ZMK log -1\r\n<\/pre>\n
      Conclusion<\/h2>\n
      This was prompted by trying to compile<\/a> the firmware for a Keychron V6 Ultra 8K<\/a> keyboard, the first step being using the main ZMK project<\/em><\/strong>, including compiling keyboard firmware for a sample keyboard (to demonstrate setting it all up actual works for a particular version on a particular version of a (Linux) system), before addressing the added complexity of Keychron’s fork.<\/p>\n
      For the current version of the main ZMK project, Python 3.12 may or may not be required, and thus LMDE 6<\/a> would be too old, with its Python 3.11.2. But reverting to an older version of ZMK and\/or using Keychron’s fork (which may be based on an older version of ZMK), it may be possible to use some older Linux systems.<\/p>\n
      References<\/h2>\n