Introduction to Zephyr RTOS

What is Zephyr?

Zephyr is a scalable, open-source real-time operating system (RTOS) designed for resource-constrained devices. It supports multiple architectures including ARM Cortex-M, RISC-V, x86, ARC, and others.

flowchart TB
    subgraph Application["Application Layer"]
        APP[Your Application]
    end

    subgraph OS["Zephyr OS Services"]
        direction TB
        NET[Networking]
        BT[Bluetooth]
        FS[File Systems]
        SHELL[Shell]
        LOG[Logging]
    end

    subgraph Kernel["Zephyr Kernel"]
        direction TB
        SCHED[Scheduler]
        SYNC[Synchronization]
        MEM[Memory Management]
        TIME[Timing Services]
    end

    subgraph HAL["Hardware Abstraction"]
        direction TB
        DRV[Device Drivers]
        DT[Device Tree]
    end

    subgraph HW["Hardware"]
        direction TB
        CPU[CPU/SoC]
        PERIPH[Peripherals]
    end

    APP --> OS
    OS --> Kernel
    Kernel --> HAL
    HAL --> HW

Key Features

Scalability

Zephyr can run on devices with as little as 8KB of RAM up to complex multi-core systems. The modular architecture lets you include only what you need.

Multiple Architecture Support

ARM: Cortex-M0/M0+/M3/M4/M7/M23/M33/M55, Cortex-A, Cortex-R
RISC-V: 32-bit and 64-bit
x86: IA-32 and x86-64
ARC: EM, HS
Others: Xtensa, SPARC, MIPS

Rich Connectivity

Networking: TCP/UDP, IPv4/IPv6, MQTT, CoAP, HTTP, WebSocket
Bluetooth: BLE 5.x, Bluetooth Mesh, Classic Bluetooth
Other: USB, CAN, LoRa, IEEE 802.15.4

Security

Memory protection (MPU/MMU)
Secure boot support
TLS/DTLS with mbedTLS
PSA (Platform Security Architecture) support

History and Governance

Zephyr started as an internal project at Wind River and was open-sourced in 2016. It’s now a Linux Foundation project with contributions from major companies:

Intel
Nordic Semiconductor
NXP
STMicroelectronics
Texas Instruments
Google
Meta
And many others

When to Use Zephyr

Zephyr is ideal for:

Use Case	Why Zephyr
IoT devices	Rich connectivity stacks, low power support
Wearables	Small footprint, Bluetooth support
Industrial sensors	Real-time guarantees, safety features
Smart home	Thread/Matter support, low power
Medical devices	Deterministic behavior, security
Automotive	Safety features, CAN support

Zephyr vs Other RTOS

Feature	Zephyr	FreeRTOS	RIOT	Bare Metal
License	Apache 2.0	MIT	LGPL	N/A
Connectivity	Extensive	Basic	Good	Manual
Driver ecosystem	Large	Varies	Medium	Manual
Build system	CMake/west	Varies	Make	Manual
Learning curve	Medium	Low	Medium	Varies

Ecosystem Overview

West - The Meta-Tool

West manages Zephyr workspaces, handles multiple repositories, and provides build/flash/debug commands.

Device Tree

Hardware is described in device tree files (.dts), allowing the same code to run on different boards with minimal changes.

Kconfig

Configuration uses the Linux kernel’s Kconfig system, providing a consistent way to enable/disable features.

Twister

The built-in test framework runs tests across multiple boards and QEMU targets.

Community Resources

Documentation: docs.zephyrproject.org
GitHub: github.com/zephyrproject-rtos/zephyr
Discord: Zephyr Discord Server
Mailing Lists: lists.zephyrproject.org

Next Steps

Now that you understand what Zephyr is, let’s install the SDK.