Zephyr 3.5 Update

I'm happy to announce that we have completed the work to upgrade ZMK to Zephyr 3.5!

petejohanson did the upgrade work to adjust ZMK for the Zephyr changes:

• Add west flash support to all UF2 capable boards.
• Adjust for LVGL DTS/Kconfig changes
• Zephyr core API changes, including CONTAINER_OF work API changes, init priority/callback, and others

Getting The Changes

Use the following steps to update to the latest tooling in order to properly use the new ZMK changes:

User Config Repositories Using GitHub Actions

Existing user config repositories using Github Actions to build will pull down Zephyr 3.5 automatically, however if you created your user config a while ago, you may need to update it to reference our shared build configuration to leverage the correct Docker image.

1. Replace the contents of your .github/workflows/build.yml with:

   on: [push, pull_request, workflow_dispatch]
   
   jobs:
     build:
       uses: zmkfirmware/zmk/.github/workflows/build-user-config.yml@main

2. If it doesn't exist already, add a new file to your repository named build.yaml:

   # This file generates the GitHub Actions matrix
   # For simple board + shield combinations, add them
   # to the top level board and shield arrays, for more
   # control, add individual board + shield combinations to
   # the `include` property, e.g:
   #
   # board: [ "nice_nano_v2" ]
   # shield: [ "corne_left", "corne_right" ]
   # include:
   #   - board: bdn9_rev2
   #   - board: nice_nano_v2
   #     shield: reviung41
   #
   ---

and then update it as appropriate to build the right shields/boards for your configuration.

VS Code & Docker (Dev Container)

If you build locally using VS Code & Docker then:

• Pull the latest ZMK main with git pull for your ZMK checkout
• Reload the project
• If you are prompted to rebuild the remote container, click Rebuild
• Otherwise, press F1 and run Remote Containers: Rebuild Container
• Once the container has rebuilt and reloaded, run west update to pull the updated Zephyr version and its dependencies.

Once the container has rebuilt, VS Code will be running the 3.5 Docker image.

Local Host Development

The following steps will get you building ZMK locally against Zephyr 3.5:

• Run the updated toolchain installation steps, and once completed, remove the previously installed SDK version (optional, existing SDK should still work)
• Install the latest version of west by running pip3 install --user --update west.
• Pull the latest ZMK main with git pull for your ZMK checkout
• Run west update to pull the updated Zephyr version and its dependencies

From there, you should be ready to build as normal!

Board/Shield Changes

The following changes have already been completed for all boards/shields in ZMK main branch. For existing or new PRs, or out of tree boards, the following changes are necessary to properly work with the latest changes.

West Flash Support

If you have a custom board for a target that has a UF2 supporting bootloader, you can easily add support for flashing via west flash. Note that using west flash isn't mandatory, it is merely a convenient way to automate copying to the mass storage device, which you can continue to do manually. To add support, add a line to your board's board.cmake file like so:

include(${ZEPHYR_BASE}/boards/common/uf2.board.cmake)

LVGL DTS/Kconfig Changes

Two items were changed for LVGL use for displays that may need adjusting for custom shields:

DPI Kconfig Rename

The old LV_Z_DPI Kconfig symbol was promoted to a Kconfig in upstream LVGL, and is now named LV_DPI_DEF. You will need to replace this symbol in your board/shield's Kconfig.defconfig file.

SSD1306 OLED Inverse Refactor

Inverting black/white pixels has moved out of the Kconfig system and into a new DTS property. If you have a custom shield that uses an SSD1306, you should:

• Remove any override for the SSD1306_REVERSE_MODE from your Kconfig files.
• Add the new inversion-on; boolean property to the SSD1306 node in your devicetree file.

Maxim max17048 Sensor Driver

Upstream Zephyr has added a driver for the max17048 fuel gauge, but using the new fuel gauge API that ZMK does not yet consume. To avoid a conflict with the new upstream and keep our existing sensor driver, our driver has been renamed to be namespaced with a ZMK prefix. The following changes are needed for any boards using the driver:

• Change the compatible value for the node to be zmk,maxim-17048, e.g. compatible = "zmk,maxim-max17048";.
• If enabling the driver explicitly via Kconfig, rename MAX17048 to the new ZMK_MAX17048 in your Kconfig.defconfig or <board>_defconfig files.

Upcoming Changes

Moving to Zephyr 3.5 will unblock several exciting efforts that were dependent on that Zephyr release.

BLE Stability Improvements

Many users have reported various BLE issues with some hardware combinations, including challenges with updated Intel drivers, and macOS general stability problems. The Zephyr 3.5 release includes many fixes for the BT host and controller portions that, combined with some small upcoming ZMK changes, have been reported to completely resolve previous issues. Further focused testing will immediately commence to fully verify the ZMK changes before making them the default.

If you'd like to test those changes, enable CONFIG_ZMK_BLE_EXPERIMENTAL_CONN=y for your builds.

Pointer Integration

The Zephyr 3.5 release includes a new input subsystem that we will be leveraging for our upcoming pointer support. The open PR for that work is now unblocked and further testing and code review will begin to work on getting that feature integrated into ZMK as well.

Power Domains

Several power domain related changes are now available as well, which were a necessity for continued work on the improved peripheral power handling that's planned to supersede the existing "VCC cutoff" code that currently exists but causes problems for builds that include multiple powered peripherals like Displays + RGB.

Thanks!

Thanks to all the testers who have helped verify ZMK functionality on the newer Zephyr version.