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.. _introducing_zephyr:
The Zephyr OS is based on a small-footprint kernel designed for use on
resource-constrained and embedded systems: from simple embedded environmental
sensors and LED wearables to sophisticated embedded controllers, smart
watches, and IoT wireless applications.
The Zephyr kernel supports multiple architectures, including:
- ARCv2 (EM and HS) and ARCv3 (HS6X)
- ARMv6-M, ARMv7-M, and ARMv8-M (Cortex-M)
- ARMv7-A and ARMv8-A (Cortex-A, 32- and 64-bit)
- ARMv7-R, ARMv8-R (Cortex-R, 32- and 64-bit)
- Intel x86 (32- and 64-bit)
- MIPS (MIPS32 Release 1 specification)
- NIOS II Gen 2
- RISC-V (32- and 64-bit)
- Tensilica Xtensa
The full list of supported boards based on these architectures 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:
Distinguishing Features
Zephyr offers a large and ever growing number of features including:
**Extensive suite of Kernel 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 POSIX 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
**Multiple Scheduling Algorithms**
Zephyr provides a comprehensive set of thread scheduling choices:
* Cooperative and Preemptive Scheduling
* Earliest Deadline First (EDF)
* Meta IRQ scheduling implementing "interrupt bottom half" or "tasklet"
* Timeslicing: Enables time slicing between preemptible threads of equal
* Multiple queuing strategies:
* Simple linked-list ready queue
* Red/black tree ready queue
* Traditional multi-queue ready queue
**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.
**Cross Architecture**
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.
**Memory Protection**
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.
For platforms without MMU/MPU and memory constrained devices, supports
combining 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
**Compile-time resource definition**
Allows system resources to be defined at compile-time, which reduces code
size and increases performance for resource-limited systems.
**Optimized Device Driver Model**
Provides a consistent device model for configuring the drivers that are part
of the platform/system and a consistent model for initializing all the
drivers configured into the system and Allows the reuse of drivers across
platforms that have common devices/IP blocks
**Devicetree Support**
Use of :ref:`devicetree <dt-guide>` to describe hardware.
Information from devicetree is used to create the application image.
**Native Networking Stack supporting multiple protocols**
Networking support is fully featured and optimized, including LwM2M and BSD
sockets compatible support. OpenThread support (on Nordic chipsets) is also
provided - a mesh network designed to securely and reliably connect hundreds
of products around the home.
**Bluetooth Low Energy 5.0 support**
Bluetooth 5.0 compliant (ESR10) and Bluetooth Low Energy Controller support
(LE Link Layer). Includes Bluetooth mesh and a Bluetooth qualification-ready
Bluetooth controller.
* Generic Access Profile (GAP) with all possible LE roles.
* GATT (Generic Attribute Profile)
* Pairing support, including the Secure Connections feature from Bluetooth
* Clean HCI driver abstraction
* Raw HCI interface to run Zephyr as a Controller instead of a full Host
* Verified with multiple popular controllers
* Highly configurable
Mesh Support:
* Relay, Friend Node, Low-Power Node (LPN) and GATT Proxy features
* Both Provisioning bearers supported (PB-ADV & PB-GATT)
* Highly configurable, fitting in devices with at least 16k RAM
**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.
**Virtual File System Interface with LittleFS and FATFS Support**
LittleFS and FATFS Support,
FCB (Flash Circular Buffer) for memory constrained applications, and
file system enhancements for logging and configuration.
**Powerful multi-backend logging Framework**
Support for log filtering, object dumping, panic mode, multiple backends
(memory, networking, filesystem, console, ..) and integration with the shell
**User friendly and full-featured Shell interface**
A multi-instance shell subsystem with user-friendly features such as
autocompletion, wildcards, coloring, metakeys (arrows, backspace, ctrl+u,
etc.) and history. Support for static commands and dynamic sub-commands.
**Settings on non-volatile storage**
The settings subsystem gives modules a way to store persistent per-device
configuration and runtime state. Settings items are stored as key-value pair
**Non-volatile storage (NVS)**
NVS allows storage of binary blobs, strings, integers, longs, and any
combination of these.
**Native POSIX port**
Supports running Zephyr as a Linux application with support for various
subsystems and networking.
.. include:: ../../README.rst
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Fundamental Terms and Concepts
See :ref:`glossary`