The Zephyr OS is based on a small-footprint kernel designed for use on
resource-constrained systems: from simple embedded environmental sensors and LED
wearables to sophisticated smart watches and IoT wireless gateways.
The Zephyr kernel supports multiple architectures, including ARM Cortex-M, Intel
x86, ARC, NIOS II, Tensilica Xtensa, and RISC-V. The full list of supported
boards can be found :ref:`here <boards>`.
Zephyr is permissively licensed using the `Apache 2.0 license`_
(as found in the ``LICENSE`` file in the
project's `GitHub repo`_). There are some
imported or reused components of the Zephyr project that use other licensing,
as described in :ref:`Zephyr_Licensing`.
.. _Apache 2.0 license:
.. _GitHub repo: https://github.com/zephyrproject-rtos/zephyr
The Zephyr kernel offers a number of features that distinguish it from other
Combines application-specific code
with a custom kernel to create a monolithic image that gets loaded
and executed on a system's hardware. Both the application code and
kernel code execute in a single shared address space.
**Highly configurable / Modular for flexibility**
Allows an application to incorporate *only*
the capabilities it needs as it needs them, and to specify their
quantity and size.
Supports a wide variety of :ref:`supported boards<boards>` with different CPU
architectures and developer tools. Contributions have added support
for an increasing number of SoCs, platforms, and drivers.
**Compile-time resource definition**
Allows system resources
to be defined at compile-time, which reduces code size and
increases performance for resource-limited systems.
**Minimal and Configurable error checking**
Provides minimal runtime error checking
to reduce code size and increase performance. An optional error-checking
infrastructure is provided to assist in debugging during application
Implements configurable architecture-specific stack-overflow protection,
kernel object and device driver permission tracking, and thread isolation
with thread-level memory protection on x86, ARC, and ARM architectures,
userspace, and memory domains.
**Native Networking Stack supporting multiple protocols**
Networking support is fully featured and optimized, including LwM2M
and BSD sockets compatible support. Bluetooth Low Energy 5.0 support
includes BLE Mesh and a Bluetooth qualification-ready BLE controller.
OpenThread support (on Nordic chipsets) is also provided - a mesh
network designed to securely and reliably connect hundreds of products
around the home.
**Native Linux, macOS, and Windows Development**
A command-line CMake build environment runs on popular developer OS
systems. A native POSIX port, lets you build and run Zephyr as a native
application on Linux and other OSes, aiding development and testing.
**Extensive suite of services**
Zephyr offers a number of familiar services for development:
* *Multi-threading Services* for cooperative, priority-based,
non-preemptive, and preemptive threads with optional round robin
time-slicing. Includes pthreads compatible API support.
* *Interrupt Services* for compile-time registration of interrupt handlers.
* *Memory Allocation Services* for dynamic allocation and freeing of
fixed-size or variable-size memory blocks.
* *Inter-thread Synchronization Services* for binary semaphores,
counting semaphores, and mutex semaphores.
* *Inter-thread Data Passing Services* for basic message queues, enhanced
message queues, and byte streams.
* *Power Management Services* such as tickless idle and an advanced idling
* *File system* with Newtron Flash Filesystem (NFFS) and FATFS
support, FCB (Flash Circular Buffer) for memory constrained
applications, and file system enhancements for logging and
* *ZTest infrastructure* and a coverage test suite for continuous
integration testing and verification as features are added and updated.
.. include:: ../../README.rst
Fundamental Terms and Concepts