1.. _introducing_zephyr: 2 3Introduction 4############ 5 6The Zephyr OS is based on a small-footprint kernel designed for use on 7resource-constrained and embedded systems: from simple embedded environmental 8sensors and LED wearables to sophisticated embedded controllers, smart 9watches, and IoT wireless applications. 10 11The Zephyr kernel supports multiple architectures, including: 12 - ARCv2 (EM and HS) and ARCv3 (HS6X) 13 - ARMv6-M, ARMv7-M, and ARMv8-M (Cortex-M) 14 - ARMv7-A and ARMv8-A (Cortex-A, 32- and 64-bit) 15 - ARMv7-R, ARMv8-R (Cortex-R, 32- and 64-bit) 16 - Intel x86 (32- and 64-bit) 17 - MIPS (MIPS32 Release 1 specification) 18 - NIOS II Gen 2 19 - RISC-V (32- and 64-bit) 20 - SPARC V8 21 - Tensilica Xtensa 22 23The full list of supported boards based on these architectures can be found :ref:`here <boards>`. 24 25Licensing 26********* 27 28Zephyr is permissively licensed using the `Apache 2.0 license`_ 29(as found in the ``LICENSE`` file in the 30project's `GitHub repo`_). There are some 31imported or reused components of the Zephyr project that use other licensing, 32as described in :ref:`Zephyr_Licensing`. 33 34.. _Apache 2.0 license: 35 https://github.com/zephyrproject-rtos/zephyr/blob/main/LICENSE 36 37.. _GitHub repo: https://github.com/zephyrproject-rtos/zephyr 38 39 40Distinguishing Features 41*********************** 42 43Zephyr offers a large and ever growing number of features including: 44 45**Extensive suite of Kernel services** 46 Zephyr offers a number of familiar services for development: 47 48 * *Multi-threading Services* for cooperative, priority-based, 49 non-preemptive, and preemptive threads with optional round robin 50 time-slicing. Includes POSIX pthreads compatible API support. 51 52 * *Interrupt Services* for compile-time registration of interrupt handlers. 53 54 * *Memory Allocation Services* for dynamic allocation and freeing of 55 fixed-size or variable-size memory blocks. 56 57 * *Inter-thread Synchronization Services* for binary semaphores, 58 counting semaphores, and mutex semaphores. 59 60 * *Inter-thread Data Passing Services* for basic message queues, enhanced 61 message queues, and byte streams. 62 63 * *Power Management Services* such as overarching, application or 64 policy-defined, System Power Management and fine-grained, driver-defined, 65 Device Power Management. 66 67**Multiple Scheduling Algorithms** 68 Zephyr provides a comprehensive set of thread scheduling choices: 69 70 * Cooperative and Preemptive Scheduling 71 * Earliest Deadline First (EDF) 72 * Meta IRQ scheduling implementing "interrupt bottom half" or "tasklet" 73 behavior 74 * Timeslicing: Enables time slicing between preemptible threads of equal 75 priority 76 * Multiple queuing strategies: 77 78 * Simple linked-list ready queue 79 * Red/black tree ready queue 80 * Traditional multi-queue ready queue 81 82**Highly configurable / Modular for flexibility** 83 Allows an application to incorporate *only* the capabilities it needs as it 84 needs them, and to specify their quantity and size. 85 86**Cross Architecture** 87 Supports a wide variety of :ref:`supported boards<boards>` with different CPU 88 architectures and developer tools. Contributions have added support 89 for an increasing number of SoCs, platforms, and drivers. 90 91**Memory Protection** 92 Implements configurable architecture-specific stack-overflow protection, 93 kernel object and device driver permission tracking, and thread isolation 94 with thread-level memory protection on x86, ARC, and ARM architectures, 95 userspace, and memory domains. 96 97 For platforms without MMU/MPU and memory constrained devices, supports 98 combining application-specific code with a custom kernel to create a 99 monolithic image that gets loaded and executed on a system's hardware. Both 100 the application code and kernel code execute in a single shared address 101 space. 102 103**Compile-time resource definition** 104 Allows system resources to be defined at compile-time, which reduces code 105 size and increases performance for resource-limited systems. 106 107**Optimized Device Driver Model** 108 Provides a consistent device model for configuring the drivers that are part 109 of the platform/system and a consistent model for initializing all the 110 drivers configured into the system and Allows the reuse of drivers across 111 platforms that have common devices/IP blocks 112 113**Devicetree Support** 114 Use of :ref:`devicetree <dt-guide>` to describe hardware. 115 Information from devicetree is used to create the application image. 116 117**Native Networking Stack supporting multiple protocols** 118 Networking support is fully featured and optimized, including LwM2M and BSD 119 sockets compatible support. OpenThread support (on Nordic chipsets) is also 120 provided - a mesh network designed to securely and reliably connect hundreds 121 of products around the home. 122 123**Bluetooth Low Energy 5.0 support** 124 Bluetooth 5.0 compliant (ESR10) and Bluetooth Low Energy Controller support 125 (LE Link Layer). Includes Bluetooth mesh and a Bluetooth qualification-ready 126 Bluetooth controller. 127 128 * Generic Access Profile (GAP) with all possible LE roles. 129 * GATT (Generic Attribute Profile) 130 * Pairing support, including the Secure Connections feature from Bluetooth 131 4.2 132 * Clean HCI driver abstraction 133 * Raw HCI interface to run Zephyr as a Controller instead of a full Host 134 stack 135 * Verified with multiple popular controllers 136 * Highly configurable 137 138 Mesh Support: 139 140 * Relay, Friend Node, Low-Power Node (LPN) and GATT Proxy features 141 * Both Provisioning bearers supported (PB-ADV & PB-GATT) 142 * Highly configurable, fitting in devices with at least 16k RAM 143 144**Native Linux, macOS, and Windows Development** 145 A command-line CMake build environment runs on popular developer OS 146 systems. A native POSIX port, lets you build and run Zephyr as a native 147 application on Linux and other OSes, aiding development and testing. 148 149**Virtual File System Interface with LittleFS and FATFS Support** 150 LittleFS and FATFS Support, 151 FCB (Flash Circular Buffer) for memory constrained applications, and 152 file system enhancements for logging and configuration. 153 154**Powerful multi-backend logging Framework** 155 Support for log filtering, object dumping, panic mode, multiple backends 156 (memory, networking, filesystem, console, ..) and integration with the shell 157 subsystem. 158 159**User friendly and full-featured Shell interface** 160 A multi-instance shell subsystem with user-friendly features such as 161 autocompletion, wildcards, coloring, metakeys (arrows, backspace, ctrl+u, 162 etc.) and history. Support for static commands and dynamic sub-commands. 163 164**Settings on non-volatile storage** 165 The settings subsystem gives modules a way to store persistent per-device 166 configuration and runtime state. Settings items are stored as key-value pair 167 strings. 168 169**Non-volatile storage (NVS)** 170 NVS allows storage of binary blobs, strings, integers, longs, and any 171 combination of these. 172 173**Native POSIX port** 174 Supports running Zephyr as a Linux application with support for various 175 subsystems and networking. 176 177 178.. include:: ../../README.rst 179 :start-after: start_include_here 180 181 182Fundamental Terms and Concepts 183****************************** 184 185See :ref:`glossary` 186
