The Zephyr Project (also just called Zephyr, which will be used for the remainder of this page) is a real-time operating system designed for resource-constrained devices such as microcontrollers. Is is part of the Linux Foundation.
Zephyr provides cooperative and preemptive scheduling.
Uses a CMake build environment.
Zephyr is cross-platform (i.e. you can build projects and flash embedded devices) and supported on Linux, Windows and macOS. However, you will experience the least amount of issues and friction running Zephyr on Linux. Linux is also the only platform currently supported by the Zephyr SDK.
Zephyr is also a platform supported by the PlatformIO build system and IDE.
The easiest way to install Zephyr on Windows is to use the chocolatey package manager. Once that is installed, run the following steps from an elevated command prompt:
Make sure to use a command-prompt and not PowerShell, as PowerShell does not play nice with the
set method of defining environment variables.
Enable global confirmation so that you don’t have to manually confirm the installation of individual programs:
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> choco feature enable -n allowGlobalConfirmation Chocolatey v0.10.15 Enabled allowGlobalConfirmation
Install Zephyr dependencies:
> choco install cmake --installargs 'ADD_CMAKE_TO_PATH=System' > choco install ninja gperf python git
If you already have some of these packages installed on your machine via means other than chocolatey, it’s advisable to remove them from the above command so you don’t install them again and have one program shadow/conflict the other.
Install the Zephyr command-line tool called
west(NOTE: I have run into problems using a Python virtual environment, so I install
westto the OS version of Python, more on this below):
> pip install west
Create a new Zephyr project:
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> west init myproject === Initializing in C:\Users\gbmhunter\myproject --- Cloning manifest repository from https://github.com/zephyrproject-rtos/zephyr, rev. master Initialized empty Git repository in C:/Users/gbmhunter/myproject/.west/manifest-tmp/.git/ remote: Enumerating objects: 55, done. remote: Counting objects: 100% (55/55), done. remote: Compressing objects: 100% (42/42), done. ... ... Branch 'master' set up to track remote branch 'master' from 'origin'. --- setting manifest.path to zephyr === Initialized. Now run "west update" inside C:\Users\gbmhunter\zephyrproject.
WARNING: I got the following error when trying to use a Python virtual environment rather than the OS Python environment to install west and then run
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> python -m venv .venv > .\.venv\Scripts\activate > pip install west > west init myproject Updating files: 100% (14758/14758), done. Already on 'master' Branch 'master' set up to track remote branch 'master' from 'origin'. Traceback (most recent call last): File "C:\Users\gbmhunter\AppData\Local\Programs\Python\Python38-32\lib\shutil.py", line 788, in move os.rename(src, real_dst) PermissionError: [WinError 5] Access is denied: 'C:\\Users\\gbmhunter\\myproject\\.west\\manifest-tmp' -> 'C:\\Users\\gbmhunter\\myproject\\zephyr'
Change into the project directory and run
> west update
This command can take a few minutes to run as it clones a number of repositories into the project directory.
Export a Zephyr CMake package to your local CMake user package registry. This allows CMake to automatically find a Zephyr “base”:
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> west zephyr-export Zephyr (C:/Users/gbmhunter/zephyrproject/zephyr/share/zephyr-package/cmake) has been added to the user package registry in: HKEY_CURRENT_USER\Software\Kitware\CMake\Packages\Zephyr ZephyrUnittest (C:/Users/gbmhunter/zephyrproject/zephyr/share/zephyrunittest-package/cmake) has been added to the user package registry in: HKEY_CURRENT_USER\Software\Kitware\CMake\Packages\ZephyrUnittest
Download and install the GNU Arm Embedded Toolchain from https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm/downloads. By default it will want to be installed on your system at
C:\Program Files (x86)\GNU Arm Embedded Toolchain\10 2020-q4-major>, but don’t let it! Zephyr does not like spaces in the path, so install it to a path which has none. I chose
Setup environment variables:
set ZEPHYR_TOOLCHAIN_VARIANT=gnuarmemb set GNUARMEMB_TOOLCHAIN_PATH=C:\gnu-arm-embedded-toolchain\10-2020-q4-major
Install the Python dependencies that Zephyr
Build the application! For this example I will be using the ST NUCLEO F070RB development board. Note that you can’t build this from the project root directory, first you have to change into the
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> cd .\zephyr > west build -b nucleo_f070rb samples/basic/blinky C:\Users\gbmhunter\temp\myproject\zephyr>west build -b nucleo_f070rb samples/basic/blinky [121/128] Linking C executable zephyr\zephyr_prebuilt.elf [128/128] Linking C executable zephyr\zephyr.elf Memory region Used Size Region Size %age Used FLASH: 13544 B 128 KB 10.33% SRAM: 4416 B 16 KB 26.95% IDT_LIST: 0 GB 2 KB 0.00%
Install OpenOCD from https://github.com/xpack-dev-tools/openocd-xpack/releases. I extracted the .zip file and then copied the files to
Flash the application:
NOTE: I got an error when running this:
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File "C:\Users\gbmhunter\temp\myproject\zephyr\scripts/west_commands\runners\core.py", line 504, in require if shutil.which(program) is None: File "C:\Users\gbmhunter\AppData\Local\Programs\Python\Python38-32\lib\shutil.py", line 1365, in which if os.path.dirname(cmd): File "C:\Users\gbmhunter\AppData\Local\Programs\Python\Python38-32\lib\ntpath.py", line 223, in dirname return split(p) File "C:\Users\gbmhunter\AppData\Local\Programs\Python\Python38-32\lib\ntpath.py", line 185, in split p = os.fspath(p) TypeError: expected str, bytes or os.PathLike object, not NoneType
Install system dependencies:
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sudo apt install --no-install-recommends git cmake ninja-build gperf \ ccache dfu-util device-tree-compiler wget \ python3-dev python3-pip python3-setuptools python3-tk python3-wheel xz-utils file \ make gcc gcc-multilib g++-multilib libsdl2-dev
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pip3 install --user -U west echo 'export PATH=~/.local/bin:"$PATH"' >> ~/.bashrc source ~/.bashrc
Get the Zephyr source code:
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west init ~/zephyrproject cd ~/zephyrproject west update ``
Export a Zephyr CMake package:
Download the Zephyr SDK:
cd ~ wget https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v0.12.3/zephyr-sdk-0.12.3-x86_64-linux-setup.run
Install the Zephyr SDK:
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$ chmod +x zephyr-sdk-0.12.3-x86_64-linux-setup.run $ sudo ./zephyr-sdk-0.12.3-x86_64-linux-setup.run -- -d /opt/zephyr-sdk-0.12.3 Verifying archive integrity... 100% All good. Uncompressing SDK for Zephyr 100% Installing SDK to /opt/zephyr-sdk-0.12.3 Creating directory /opt/zephyr-sdk-0.12.3 Success [*] Installing arm tools... [*] Installing arm64 tools... [*] Installing arc tools... [*] Installing nios2 tools... [*] Installing riscv64 tools... [*] Installing sparc tools... [*] Installing mips tools... [*] Installing x86_64 tools... [*] Installing xtensa_sample_controller tools... [*] Installing xtensa_intel_apl_adsp tools... [*] Installing xtensa_intel_s1000 tools... [*] Installing xtensa_intel_bdw_adsp tools... [*] Installing xtensa_intel_byt_adsp tools... [*] Installing xtensa_nxp_imx_adsp tools... [*] Installing xtensa_nxp_imx8m_adsp tools... [*] Installing CMake files... [*] Installing additional host tools... Success installing SDK. SDK is ready to be used.
You don’t have to install into
/opt/if you don’t want to. Installing into your home directory is also valid.
sudo cp /opt/zephyr-sdk-0.12.3/sysroots/x86_64-pokysdk-linux/usr/share/openocd/contrib/60-openocd.rules /etc/udev/rules.d sudo udevadm control --reload
zephyrdirectory (a sub-directory of the project directory) and build the Blinky sample:
cd ~/zephyrproject/zephyr west build -p auto -b nucleo_f070rb samples/basic/blinky
Make sure the dev. kit is plugged into the computer, and then flash the application onto the dev kit (remember we were using the NUCLEO-F070RB for this example):
Hardware Abstraction Layers
Examples of some of the HALs (which are installed under
<project root dir>/modules/hal/) supported by Zephyr:
The Zephyr SDK contains toolchains to compile, assemble, link and program/debug Zephyr applications. Currently it is only supported on Linux. On Windows and macOS, you have to manually install the toolchains you require for your Zephyr application.
See https://docs.zephyrproject.org/latest/boards/index.html#boards for a comprehensive list of all the development boards supported by the Zephyr platform.
Example device tree (for the STM32F070RB development board):
The latest documentation for peripheral (UART, SPI, PWM, PIN, e.t.c.) APIs can be found at https://docs.zephyrproject.org/latest/reference/peripherals/index.html.
What Does A Basic Zephyr Firmware Application Look Like?
The following example shows
main.c (the only
.c file) for the
Blinky sample project:
Zephyr supports the targets
qemu_cortex_m3 for running Zephyr applications on desktop computers. This is great for development, testing and CICD purposes.
Un-supported C++ Features
There are a number of C++ features that Zephyr does not support which removes C++ as a 1st tier language for writing Zephyr applications. This includes:
- No dynamic memory allocation support via
delete. Dynamic memory allocation in the embedded land is a contentious subject, but it’s nice to be able to use it if it’s a suitable choice for your application.
- No RTTI (run-time type information)
- No support for exceptions. Again, another contentious embedded subject, but nice to have the option of using them if you want.
File not found (on Windows)
If you get an error when running
west build similar to:
It is due to there being one or more spaces in the path to your Zephyr project directory. This isn’t a bug that is going to be fixed anytime soon, Zephyr is very clear on the matter in their documentation:
I found this out the hard way and went through all the trouble of renaming my user directory to fix the issue.
No module named ’elftools'
You typically get the error
No module named 'elftools' if you haven’t installed the Python modules that Zephyr requires to build. To install the required modules:
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