This is the documentation for the latest (master) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

Beyond the Getting Started Guide

The Getting Started Guide gives a straight-forward path to set up your Linux, macOS, or Windows environment for Zephyr development. In this document, we delve deeper into Zephyr development setup issues and alternatives.

Python and pip

Python 3 and its package manager, pip1, are used extensively by Zephyr to install and run scripts required to compile and run Zephyr applications, set up and maintain the Zephyr development environment, and build project documentation.

Depending on your operating system, you may need to provide the --user flag to the pip3 command when installing new packages. This is documented throughout the instructions. See Installing Packages in the Python Packaging User Guide for more information about pip1, including information on -\-user.

  • On Linux, make sure ~/.local/bin is at the front of your PATH environment variable, or programs installed with --user won’t be found. Installing with --user avoids conflicts between pip and the system package manager, and is the default on Debian-based distributions.

  • On macOS, Homebrew disables -\-user.

  • On Windows, see the Installing Packages information on --user if you require using this option.

On all operating systems, pip’s -U flag installs or updates the package if the package is already installed locally but a more recent version is available. It is good practice to use this flag if the latest version of a package is required. (Check the scripts/requirements.txt file to see if a specific Python package version is expected.)

Advanced Setup and tool chain alternatives

Here are some alternative instructions for more advanced platform setup configurations for supported development platforms:

Set Up a Toolchain

Zephyr binaries are compiled and linked by a toolchain comprised of a cross-compiler and related tools which are different than the compiler and tools used for developing software that runs natively on your operating system.

On Linux systems, you can install the Zephyr SDK to get toolchains for all supported architectures. Otherwise, you can install other toolchains in the usual way for your operating system: with installer programs or system package managers, by downloading and extracting a zip archive, etc.

You configure the Zephyr build system to use a specific toolchain by setting environment variables such as ZEPHYR_TOOLCHAIN_VARIANT to a supported value, along with additional variable(s) specific to the toolchain variant.

While the Zephyr SDK includes standard tool chains for all supported architectures, there are also customized alternatives as described in these documents. (If you’re not sure which to use, check your specific board-level documentation. If you’re targeting an Arm Cortex-M board, for example, GNU ARM Embedded is a safe bet.)

Cloning the Zephyr Repositories

The Zephyr project source is maintained in the GitHub zephyr repo. External modules used by Zephyr are found in the parent GitHub Zephyr project. Because of these dependencies, it’s convenient to use the Zephyr-created west tool to fetch and manage the Zephyr and external module source code. See Basics for more details.

Once your development tools are installed, use West (Zephyr’s meta-tool) to create, initialize, and download sources from the zephyr and external module repos. We’ll use the name zephyrproject, but you can choose any name that does not contain a space anywhere in the path.

west init zephyrproject
cd zephyrproject
west update

The west update command fetches and keeps Modules (External projects) in the zephyrproject folder in sync with the code in the local zephyr repo.


You must run west update any time the zephyr/west.yml changes, caused, for example, when you pull the zephyr repository, switch branches in it, or perform a git bisect inside of it.

Keeping Zephyr updated

To update the Zephyr project source code, you need to get the latest changes via git. Afterwards, run west update as mentioned in the previous paragraph.

# replace zephyrproject with the path you gave west init
cd zephyrproject/zephyr
git pull
west update

Export Zephyr CMake package

The Zephyr CMake Package can be exported to CMake’s user package registry if it has not already been done as part of Getting Started Guide.

Board Aliases

Developers who work with multiple boards may find explicit board names cumbersome and want to use aliases for common targets. This is supported by a CMake file with content like this:

# Variable foo_BOARD_ALIAS=bar replaces BOARD=foo with BOARD=bar and
# sets BOARD_ALIAS=foo in the CMake cache.
set(pca10028_BOARD_ALIAS nrf51dk_nrf51422)
set(pca10056_BOARD_ALIAS nrf52840dk_nrf52840)
set(k64f_BOARD_ALIAS frdm_k64f)
set(sltb004a_BOARD_ALIAS efr32mg_sltb004a)

and specifying its location in ZEPHYR_BOARD_ALIASES. This enables use of aliases pca10028 in contexts like cmake -DBOARD=pca10028 and west -b pca10028.

Build and Run an Application

You can build, flash, and run Zephyr applications on real hardware using a supported host system. Depending on your operating system, you can also run it in emulation with QEMU, or as a native POSIX application. Additional information about building applications can be found in the Building an Application section.

Build Blinky

Let’s build the Blinky sample application.

Zephyr applications are built to run on specific hardware, called a “board”2. We’ll use the Phytec reel_board here, but you can change the reel_board build target to another value if you have a different board. See Supported Boards or run west boards from anywhere inside the zephyrproject directory for a list of supported boards.

  1. Go to the zephyr repository:

    cd zephyrproject/zephyr
  2. Build the blinky sample for the reel_board:

    west build -b reel_board samples/basic/blinky

The main build products will be in build/zephyr; build/zephyr/zephyr.elf is the blinky application binary in ELF format. Other binary formats, disassembly, and map files may be present depending on your board.

The other sample applications in the samples folder are documented in Samples and Demos.


If you want to re-use an existing build directory for another board or application, you need to add the parameter -p=auto to west build to clean out settings and artifacts from the previous build.

Run the Application by Flashing to a Board

Most hardware boards supported by Zephyr can be flashed by running west flash. This may require board-specific tool installation and configuration to work properly.

See Run an Application and your specific board’s documentation in Supported Boards for additional details.

Setting udev rules

Flashing a board requires permission to directly access the board hardware, usually managed by installation of the flashing tools. On Linux systems, if the west flash command fails, you likely need to define udev rules to grant the needed access permission.

Udev is a device manager for the Linux kernel and the udev daemon handles all user space events raised when a hardware device is added (or removed) from the system. We can add a rules file to grant access permission by non-root users to certain USB-connected devices.

The OpenOCD (On-Chip Debugger) project conveniently provides a rules file that defined board-specific rules for most Zephyr-supported arm-based boards, so we recommend installing this rules file by downloading it from their sourceforge repo, or if you’ve installed the Zephyr SDK there is a copy of this rules file in the SDK folder:

  • Either download the OpenOCD rules file and copy it to the right location:

    wget -O 60-openocd.rules
    sudo cp 60-openocd.rules /etc/udev/rules.d
  • or copy the rules file from the Zephyr SDK folder:

    sudo cp ${ZEPHYR_SDK_INSTALL_DIR}/sysroots/x86_64-pokysdk-linux/usr/share/openocd/contrib/60-openocd.rules /etc/udev/rules.d

Then, in either case, ask the udev daemon to reload these rules:

sudo udevadm control --reload

Unplug and plug in the USB connection to your board, and you should have permission to access the board hardware for flashing. Check your board-specific documentation (Supported Boards) for further information if needed.

Run the Application in QEMU

On Linux and macOS, you can run Zephyr applications via emulation on your host system using QEMU when targeting either the x86 or ARM Cortex-M3 architectures. (QEMU is included with the Zephyr SDK installation.)

For example, you can build and run the Hello World sample using the x86 emulation board configuration (qemu_x86), with:

# From the root of the zephyr repository
west build -b qemu_x86 samples/hello_world
west build -t run

To exit QEMU, type Ctrl-a, then x.

Use qemu_cortex_m3 to target an emulated Arm Cortex-M3 sample.

Run a Sample Application natively (POSIX OS)

You can compile some samples to run as host processes on a POSIX OS. This is currently only tested on Linux hosts. See Native POSIX execution (native_posix) for more information. On 64-bit host operating systems, you need to install a 32-bit C library; see Host system dependencies for details.

First, build Hello World for native_posix.

# From the root of the zephyr repository
west build -b native_posix samples/hello_world

Next, run the application.

west build -t run
# or just run zephyr.exe directly:

Press Ctrl-C to exit.

You can run ./build/zephyr/zephyr.exe --help to get a list of available options.

This executable can be instrumented using standard tools, such as gdb or valgrind.



pip is Python’s package installer. Its install command first tries to re-use packages and package dependencies already installed on your computer. If that is not possible, pip install downloads them from the Python Package Index (PyPI) on the Internet.

The package versions requested by Zephyr’s requirements.txt may conflict with other requirements on your system, in which case you may want to set up a virtualenv for Zephyr development.


This has become something of a misnomer over time. While the target can be, and often is, a microprocessor running on its own dedicated hardware board, Zephyr also supports using QEMU to run targets built for other architectures in emulation, targets which produce native host system binaries that implement Zephyr’s driver interfaces with POSIX APIs, and even running different Zephyr-based binaries on CPU cores of differing architectures on the same physical chip. Each of these hardware configurations is called a “board,” even though that doesn’t always make perfect sense in context.