185 lines
7.0 KiB
ReStructuredText
185 lines
7.0 KiB
ReStructuredText
.. _introducing_zephyr:
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Introduction
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############
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The Zephyr OS is based on a small-footprint kernel designed for use on
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resource-constrained and embedded systems: from simple embedded environmental
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sensors and LED wearables to sophisticated embedded controllers, smart
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watches, and IoT wireless applications.
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The Zephyr kernel supports multiple architectures, including:
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- ARCv2 (EM and HS) and ARCv3 (HS6X)
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- ARMv6-M, ARMv7-M, and ARMv8-M (Cortex-M)
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- ARMv7-A and ARMv8-A (Cortex-A, 32- and 64-bit)
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- ARMv7-R, ARMv8-R (Cortex-R, 32- and 64-bit)
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- Intel x86 (32- and 64-bit)
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- MIPS (MIPS32 Release 1 specification)
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- NIOS II Gen 2
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- RISC-V (32- and 64-bit)
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- SPARC V8
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- Tensilica Xtensa
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The full list of supported boards based on these architectures can be found :ref:`here <boards>`.
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Licensing
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*********
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Zephyr is permissively licensed using the `Apache 2.0 license`_
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(as found in the ``LICENSE`` file in the
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project's `GitHub repo`_). There are some
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imported or reused components of the Zephyr project that use other licensing,
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as described in :ref:`Zephyr_Licensing`.
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.. _Apache 2.0 license:
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https://github.com/zephyrproject-rtos/zephyr/blob/main/LICENSE
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.. _GitHub repo: https://github.com/zephyrproject-rtos/zephyr
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Distinguishing Features
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***********************
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Zephyr offers a large and ever growing number of features including:
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**Extensive suite of Kernel services**
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Zephyr offers a number of familiar services for development:
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* *Multi-threading Services* for cooperative, priority-based,
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non-preemptive, and preemptive threads with optional round robin
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time-slicing. Includes POSIX pthreads compatible API support.
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* *Interrupt Services* for compile-time registration of interrupt handlers.
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* *Memory Allocation Services* for dynamic allocation and freeing of
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fixed-size or variable-size memory blocks.
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* *Inter-thread Synchronization Services* for binary semaphores,
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counting semaphores, and mutex semaphores.
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* *Inter-thread Data Passing Services* for basic message queues, enhanced
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message queues, and byte streams.
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* *Power Management Services* such as tickless idle and an advanced idling
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infrastructure.
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**Multiple Scheduling Algorithms**
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Zephyr provides a comprehensive set of thread scheduling choices:
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* Cooperative and Preemptive Scheduling
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* Earliest Deadline First (EDF)
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* Meta IRQ scheduling implementing "interrupt bottom half" or "tasklet"
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behavior
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* Timeslicing: Enables time slicing between preemptible threads of equal
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priority
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* Multiple queuing strategies:
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* Simple linked-list ready queue
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* Red/black tree ready queue
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* Traditional multi-queue ready queue
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**Highly configurable / Modular for flexibility**
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Allows an application to incorporate *only* the capabilities it needs as it
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needs them, and to specify their quantity and size.
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**Cross Architecture**
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Supports a wide variety of :ref:`supported boards<boards>` with different CPU
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architectures and developer tools. Contributions have added support
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for an increasing number of SoCs, platforms, and drivers.
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**Memory Protection**
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Implements configurable architecture-specific stack-overflow protection,
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kernel object and device driver permission tracking, and thread isolation
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with thread-level memory protection on x86, ARC, and ARM architectures,
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userspace, and memory domains.
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For platforms without MMU/MPU and memory constrained devices, supports
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combining application-specific code with a custom kernel to create a
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monolithic image that gets loaded and executed on a system's hardware. Both
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the application code and kernel code execute in a single shared address
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space.
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**Compile-time resource definition**
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Allows system resources to be defined at compile-time, which reduces code
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size and increases performance for resource-limited systems.
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**Optimized Device Driver Model**
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Provides a consistent device model for configuring the drivers that are part
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of the platform/system and a consistent model for initializing all the
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drivers configured into the system and Allows the reuse of drivers across
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platforms that have common devices/IP blocks
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**Devicetree Support**
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Use of :ref:`devicetree <dt-guide>` to describe hardware.
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Information from devicetree is used to create the application image.
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**Native Networking Stack supporting multiple protocols**
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Networking support is fully featured and optimized, including LwM2M and BSD
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sockets compatible support. OpenThread support (on Nordic chipsets) is also
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provided - a mesh network designed to securely and reliably connect hundreds
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of products around the home.
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**Bluetooth Low Energy 5.0 support**
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Bluetooth 5.0 compliant (ESR10) and Bluetooth Low Energy Controller support
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(LE Link Layer). Includes Bluetooth mesh and a Bluetooth qualification-ready
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Bluetooth controller.
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* Generic Access Profile (GAP) with all possible LE roles.
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* GATT (Generic Attribute Profile)
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* Pairing support, including the Secure Connections feature from Bluetooth
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4.2
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* Clean HCI driver abstraction
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* Raw HCI interface to run Zephyr as a Controller instead of a full Host
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stack
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* Verified with multiple popular controllers
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* Highly configurable
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Mesh Support:
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* Relay, Friend Node, Low-Power Node (LPN) and GATT Proxy features
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* Both Provisioning bearers supported (PB-ADV & PB-GATT)
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* Highly configurable, fitting in devices with at least 16k RAM
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**Native Linux, macOS, and Windows Development**
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A command-line CMake build environment runs on popular developer OS
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systems. A native POSIX port, lets you build and run Zephyr as a native
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application on Linux and other OSes, aiding development and testing.
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**Virtual File System Interface with LittleFS and FATFS Support**
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LittleFS and FATFS Support,
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FCB (Flash Circular Buffer) for memory constrained applications, and
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file system enhancements for logging and configuration.
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**Powerful multi-backend logging Framework**
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Support for log filtering, object dumping, panic mode, multiple backends
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(memory, networking, filesystem, console, ..) and integration with the shell
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subsystem.
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**User friendly and full-featured Shell interface**
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A multi-instance shell subsystem with user-friendly features such as
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autocompletion, wildcards, coloring, metakeys (arrows, backspace, ctrl+u,
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etc.) and history. Support for static commands and dynamic sub-commands.
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**Settings on non-volatile storage**
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The settings subsystem gives modules a way to store persistent per-device
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configuration and runtime state. Settings items are stored as key-value pair
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strings.
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**Non-volatile storage (NVS)**
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NVS allows storage of binary blobs, strings, integers, longs, and any
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combination of these.
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**Native POSIX port**
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Supports running Zephyr as a Linux application with support for various
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subsystems and networking.
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.. include:: ../../README.rst
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:start-after: start_include_here
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Fundamental Terms and Concepts
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******************************
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See :ref:`glossary`
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