- Optimization for low-powered, small memory footprint devices.
- Powerful hardware abstraction and configuration using [DeviceTree](https://docs.zephyrproject.org/latest/guides/dts/index.html) and [Kconfig](https://docs.zephyrproject.org/latest/guides/kconfig/index.html).
- A BLE stack that periodically obtains [qualification](https://docs.zephyrproject.org/latest/guides/bluetooth/bluetooth-qual.html) listings, making it easier for final products to obtain qualification from the Bluetooth® SIG.
- Multi-processor support, which is critical for power efficiency in upcoming MCUs.
- A buzzing developer [community](https://github.com/zephyrproject-rtos/zephyr) including many leading [embedded technology](https://www.zephyrproject.org/project-members) companies.
- Just like other open source firmware, ZMK is all about the free and the sharing. However, some other projects use the GPL license which prevents integration of libraries and drivers whose licenses are not GPL-compatible (such as some embedded BLE drivers). ZMK uses the permissive [MIT](https://github.com/zmkfirmware/zmk/blob/main/LICENSE) license which doesn’t have this limitation.
- ZMK is designed for the future, and we believe the future is wireless. So power efficiency plays a critical role in every design decision, just like in Zephyr™.
The Zephyr™ [documentation](https://docs.zephyrproject.org/latest/boards/index.html) describes which hardware is currently natively supported by the Zephyr™ platform. _Similar documentation covering which keyboards have been integrated into ZMK is currently being planned._
ZMK is still in its infancy, so there’s a learning curve involved. But if you’d like to try it out, please check out the development [documentation](/docs) and the other FAQs. Please keep in mind that the project team is still small, so our support capability is limited whilst we focus on development. But we’ll try our best! Interested developers are also very welcome to contribute!
- Complete keyboard PCBs that include the MCU (e.g. the Planck or Preonic).
- Small MCU boards (e.g. the Proton-C or nice!nano) that expose pins and are designed to be combined with larger keyboard PCBs, or hand wired to switches to create the final keyboard.
In ZMK, a _shield_ is a _PCB_ or _hardwired set of components_ that when combined with a MCU only [board](#what-is-a-board) like the Proton-C or nice!nano, results in a complete usable keyboard. Examples would be keyboard PCBs like the Kyria or Corne. The _shield_ is usually the big PCB containing all the keys.
When a keyboard accepts a small “PCB MCU module” (e.g. _Arduino Pro Micro_) for its “brains”, then it's important to conceptually separate the hardware into a [board](#what-is-a-board) PCB and a [shield](#what-is-a-shield) PCB.
The [shield](#what-is-a-shield) is a brainless shell containing all the keys, RGB LEDs, encoders etc. It maps all of these features to a standard pin footprint, such as the Pro Micro pinout.
To bring this brainless [shield](#what-is-a-shield) to life, you attach any MCU [board](#what-is-a-board) matching the footprint. For instance, the _nice!nano_ is _pin-compatible_ with the _Arduino Pro Micro_, so you can substitute either [board](#what-is-a-board) onto the [shield](#what-is-a-shield). But each [board](#what-is-a-board) comes with its own features (MCU, flash, BLE, etc.) which must also be handled.
Therefore in ZMK, [board](#what-is-a-board) and [shield](#what-is-a-shield) are considered two different (but related) entities so that it’s easier to mix and match them. They are combined during a ZMK build.
Please note, many keyboards only have a single PCB which includes the “brains” (MCU) onboard. In ZMK, these have no [shield](#what-is-a-shield), only a [board](#what-is-a-board).
ZMK isn’t designed for any particular bootloader, and supports flashing different boards with different flash utilities (e.g. OpenOCD, nrfjprog, etc.). So if you have any difficulties, please let us know on [Discord](https://zmk.dev/community/discord/invite)!
The exact process for the management of all the possible hardware is still being finalized, but any developer looking to contribute new keyboard definitions should chat with us on [Discord](https://zmk.dev/community/discord/invite) to get started.
ZMK was originally coined as a quasi-acronym of “Zephyr Mechanical Keyboard” and also taking inspiration from the amazing keyboard firmware projects, TMK and QMK.