In the fast-evolving world of embedded systems and IoT, selecting the right operating system is critical. For skilled and intermediate engineers, understanding where a real-time operating system (RTOS) comes from (e.g. history, evolution, and the forces driving its development) can provide valuable context for making informed technical decisions.
Zephyr, now one of the most robust open-source RTOS platforms in the industry, didn’t emerge overnight. Its roots trace back to commercial RTOSes developed in the 1990s and 2000s, with its evolution shaped by tech giants and a growing demand for a scalable, secure, and community-driven operating system for microcontroller-based systems.
👉 Check out the full Zephyr video series on DigiKey’s channel to take a hands-on deep dive into this popular RTOS.
From Virtuoso RTOS to Rocket: The Foundation
Zephyr’s origin story begins with Virtuoso, a commercial real-time operating system developed by Eonic Systems in the late 1990s. Virtuoso was a small-footprint, preemptive multitasking kernel designed for digital signal processing and embedded communications, with real-time performance at its core.
In 2006, Wind River Systems, a leading embedded software company (best known for VxWorks), acquired Eonic’s Virtuoso technology. Wind River rebranded and evolved this into a lightweight RTOS designed specifically for emerging connected devices.
What Was Rocket RTOS?
Launched around 2014, Rocket RTOS was Wind River’s effort to offer a modern, free-to-use (but not open-source) RTOS for the rapidly growing Internet of Things (IoT) market. It was intended to:
- Provide a real-time multitasking kernel
- Support microcontroller peripherals
- Offer a basic device driver model
- Deliver a footprint small enough for constrained MCU systems
Although free to use, Rocket was tied to Wind River’s proprietary ecosystem, including its development tools and commercial support offerings. Despite this, Rocket helped validate a need: developers wanted something free, reliable, and purpose-built for IoT.
Why the Linux Foundation Got Involved
By the mid-2010s, embedded Linux was thriving for higher-end systems, but there was no comparable, vendor-neutral, open-source RTOS for low-power microcontroller use. The Linux Foundation recognized this opportunity.
In 2015, the Linux Foundation began exploring ways to create a secure, scalable RTOS for constrained devices. Their goals:
- Vendor-neutral governance
- Transparent, collaborative development
- Support for multiple architectures and boards
- Built-in capabilities like Bluetooth, networking, and security
Wind River contributed key components of Rocket RTOS to seed the project. These contributions were significant in shaping the kernel and design philosophy of what would become Zephyr.
Birth of Zephyr RTOS
The Zephyr Project was officially announced by the Linux Foundation on February 17, 2016. With Wind River’s codebase as a foundation, Zephyr adopted open-source licensing (Apache 2.0) and a development model centered around transparency, modularity, and scalability.
Key innovations included:
- Hardware abstraction through Devicetree
- Software configuration via Kconfig
- Modular subsystems for drivers, networking, and file systems
- Support for Bluetooth Low Energy, Wi-Fi, TLS/SSL, and USB
- Tooling for reproducible builds (west)
Zephyr was designed to scale from simple bare-metal applications to more complex systems with threads, services, and event handling without the weight of traditional operating systems.
Notable Zephyr Release Milestones
Zephyr’s rapid development has been marked by several major milestones:
- Feb 2016 – Project launch with initial code contribution from Wind River (v0.5)
- Sep 2016 – Zephyr 1.0: first stable release, included core APIs and drivers
- Apr 2019 – Zephyr 2.0: major architecture improvements, modularization, and multicore support
- Aug 2021 – Zephyr 3.0: build optimizations, extended SoC/board support, and CI/CD enhancements
- July 2024 – Zephyr 3.7 (LTS): latest long-term support version with redesigned hardware model and expanded POSIX compliance covering most IEEE 1003-2017 system interface options
- Nov 2024 – Zephyr 4.0: introduction of a secure storage subsystem using PSA APIs, ZMS (Zephyr Memory Storage) for flexible key-value storage, and expanded hardware support with new subsystems
- Mar 2024 – Zephyr 4.1: performance optimizations, initial Rust language support, and a USB MIDI 2.0 class for audio support
Zephyr commits to providing long-term support (LTS) versions every 2.5 to 3 years, which are maintained independently for about 5 years after release. This allows embedded developers to build systems around Zephyr knowing a specific LTS version will be supported for a while. You can read more about the latest Zephyr versions here.
Companies Supporting the Zephyr Project
One of Zephyr’s key strengths lies in its broad industry backing. The Zephyr Project’s members contribute code, documentation, infrastructure, and direction.
Key Members Include:
- Intel
- Nordic Semiconductor
- NXP
- STMicroelectronics
- Texas Instruments
- Linaro
- Antmicro
- Oticon
- Meta, Arm, and others joined later
These companies integrate Zephyr into their own SDKs and products. For instance, Nordic’s nRF Connect SDK uses Zephyr as the underlying RTOS for Bluetooth and LTE applications. As more companies back and integrate Zephyr into their products, it is steadily positioning itself as a top-tier real-time operating system.
Governance and Technical Direction
Zephyr uses a multi-layer governance model:
- Governing Board – handles project direction, funding, and partnerships.
- A Technical Steering Committee (TSC) – made up of senior engineers from member companies, defines the release roadmap, architecture decisions, and merges pull requests.
- Maintainers – manages subsystems like networking, kernel, boards, and drivers.
This structured model has kept the project aligned with real-world engineering needs while supporting growth in documentation, continuous integration (CI) infrastructure, and automated testing.
Community Support
Zephyr boasts a vibrant and growing community backed by the Linux Foundation, with contributions from major tech companies, independent developers, and academic researchers. Developers using Zephyr can get help through multiple well-maintained channels, including the official Zephyr Discord server, GitHub Discussions, and the [zephyr-rtos] tag on Stack Overflow. Extensive documentation is available on the Zephyr Project website, and regular blog posts, tutorials, and conference talks keep the community informed and engaged. Contributors are active in reviewing pull requests and triaging issues, while maintainers provide guidance through subsystem-specific GitHub repositories. The project also hosts periodic developer summits and working group meetings, creating a collaborative environment where both newcomers and experienced engineers can get support and influence the direction of the RTOS.
Learn More with the Zephyr Video Series
The best way to appreciate Zephyr’s capabilities is to get your hands dirty. My free 12-part Zephyr video series covers everything from setting up the development environment to writing drivers and building connected applications.
👉 Check out the full Zephyr video series on DigiKey’s channel
Whether you’re building wearables, smart sensors, or industrial gateways, this series will help you:
- Understand Zephyr’s architecture
- Master Devicetree, Kconfig, and CMake
- Write modular, portable firmware
- Build real-world IoT systems from scratch
- Port Zephyr to custom boards
Final Thoughts
Zephyr’s journey from proprietary RTOS kernel to an open-source powerhouse exemplifies the power of collaborative engineering. What started as a commercial RTOS from Eonic became part of Wind River’s Rocket, then evolved into a Linux Foundation project reshaping embedded development.
If you’re looking for an RTOS that’s open, secure, flexible, and backed by industry leaders, Zephyr is a compelling choice. Whether you’re prototyping, teaching, or building production firmware, it offers the tools and community support to help you succeed.