177 lines
6.8 KiB
ReStructuredText
177 lines
6.8 KiB
ReStructuredText
.. _introducing_zephyr:
|
|
|
|
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 ARM Cortex-M, Intel
|
|
x86, ARC, NIOS II, Tensilica Xtensa and RISC-V 32. The full list of supported
|
|
boards can be found :ref:`here <boards>`.
|
|
|
|
Licensing
|
|
*********
|
|
|
|
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:
|
|
https://github.com/zephyrproject-rtos/zephyr/blob/master/LICENSE
|
|
|
|
.. _GitHub repo: https://github.com/zephyrproject-rtos/zephyr
|
|
|
|
|
|
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
|
|
infrastructure.
|
|
|
|
**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"
|
|
behavior
|
|
* Timeslicing: Enables time slicing between preemptible threads of equal
|
|
priority
|
|
* 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
|
|
space.
|
|
|
|
**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
|
|
|
|
**Device Tree Support**
|
|
Use of Device Tree (DTS) to describe hardware and configuration information for
|
|
boards. The DTS information will be used only during compile time.
|
|
Information about the system is extracted from the compiled DTS and 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 BLE Mesh and a Bluetooth qualification-ready BLE
|
|
controller.
|
|
|
|
* Generic Access Profile (GAP) with all possible LE roles.
|
|
* GATT (Generic Attribute Profile)
|
|
* Pairing support, including the Secure Connections feature from Bluetooth
|
|
4.2
|
|
* Clean HCI driver abstraction
|
|
* Raw HCI interface to run Zephyr as a Controller instead of a full Host
|
|
stack
|
|
* 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 NFFS and FATFS Support**
|
|
Newtron Flash Filesystem (NFFS) 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
|
|
subsystem.
|
|
|
|
**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
|
|
strings.
|
|
|
|
**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
|
|
:start-after: start_include_here
|
|
|
|
|
|
Fundamental Terms and Concepts
|
|
******************************
|
|
|
|
See :ref:`glossary`
|