Choosing the right foundation for your next embedded or IoT project can be daunting. As a skilled or intermediate embedded engineer, you know that every tool, abstraction, and framework introduces trade-offs. Whether you’re moving from bare-metal code or evaluating RTOS options for cross-platform scalability, it’s essential to understand the strengths and limitations of each.
In this article, we break down why Zephyr is emerging as one of the most versatile RTOS platforms in the embedded space. We’ll compare it to bare-metal programming, Arduino, other open-source RTOS solutions like FreeRTOS and Azure RTOS, and commercial-grade options like VxWorks and QNX.
If you’re trying to decide what’s right for your project, team, or long-term development goals, read on.
👉 Check out the full Zephyr video series on DigiKey’s channel for hands-on learning. One major complaint about Zephyr is the learning curve, and the critics are not wrong: Zephyr can be quite an undertaking to learn, especially if you’re coming from the microcontroller world and are not familiar with Kconfig and the Devicetree. In the video series, I walk you through all of these components so you can feel confident working with Zephyr’s complex configuration system (rather than fighting against it).
Zephyr: What Makes It Different?
Zephyr is an open-source real-time operating system (RTOS) maintained by the Linux Foundation. It’s not just a task scheduler. Zephyr is a full-stack embedded ecosystem that includes drivers, connectivity stacks, Devicetree-based hardware abstraction, and built-in tools for configuration, debugging, and testing. It supports a wide array of microcontroller architectures and integrates tightly with modern CI/CD workflows.
Zephyr vs. Bare-Metal Programming
Bare-metal development is where most embedded engineers start. Writing directly to registers gives you maximum control and minimal overhead. But with increasing IoT demands and more sophisticated sensors, protocols, and cloud integrations, bare-metal code becomes hard to maintain.
✅ Pros of Bare-Metal:
- Full control over timing and performance
- Minimal code size and no OS overhead
- Useful for ultra-constrained or real-time-critical applications
❌ Cons of Bare-Metal:
- No abstraction layer: hardware-specific code is hard to port
- No built-in support for concurrency, scheduling, or power management
- Time-consuming to implement drivers, protocols, and debugging tools
Where Zephyr Wins:
Zephyr abstracts hardware with Devicetree, allowing you to write truly cross-platform, professional application code. You can still write low-level code when needed, but you also gain the power of a full RTOS with Bluetooth, Wi-Fi, logging, shell, and filesystem support right out of the box.
Zephyr vs. Arduino
Arduino is a wonderful gateway into embedded programming. It simplifies setup and makes microcontrollers approachable for beginners. However, its simplicity is also its limitation when building serious, production-ready IoT systems.
✅ Pros of Arduino:
- Extremely easy to set up and use
- Great community support and libraries
- Ideal for rapid prototyping and proof-of-concept projects
❌ Cons of Arduino:
- Limited real-time control
- Single-threaded by default (depending on the platform: e.g. ESP32 Arduino port is built on a fork of FreeRTOS)
- Hard to scale into production or custom hardware
- Libraries often lack deep configurability and robust error handling
Where Zephyr Wins:
Zephyr is ideal for engineers who have outgrown Arduino. It supports real-time threading, modular configuration with Kconfig, and has a huge set of libraries for wireless connectivity and peripherals. It also supports a professional development workflow using CMake, Docker, and Git-based dependency management.
Zephyr vs. Open Source RTOS (FreeRTOS, Azure RTOS)
Both FreeRTOS and Azure RTOS are widely used and respected in the embedded community. They are lighter weight than Zephyr and often used in low-power or resource-constrained applications.
✅ Pros of FreeRTOS and Azure RTOS:
- Minimal and efficient kernel
- Easier to integrate with minimal overhead
- FreeRTOS has deep integration with AWS tools
- Azure RTOS (ThreadX) is tightly integrated with Microsoft’s IoT platform
❌ Cons of FreeRTOS and Azure RTOS:
- Limited out-of-the-box features (you must bring your own drivers and stacks)
- Less standardized tooling and inconsistent hardware abstraction
- Documentation and community support can be fragmented
Where Zephyr Wins:
Zephyr provides more than just a kernel. It’s an ecosystem with standardized APIs, hardware abstraction, and mature tooling like west (multi-repo management) and twister (test automation). If you’re developing a complex application that requires BLE, Wi-Fi, file systems, or UI elements like LVGL, Zephyr reduces integration pain and boosts maintainability.
Zephyr also has strong security support out-of-the-box, including MCUBoot, mbedTLS, and PSA Crypto. For long-term projects, Zephyr’s modularity and Linux Foundation backing offer stability and transparency.
Zephyr vs. Commercial RTOS (VxWorks, QNX)
Commercial RTOSes like VxWorks and QNX dominate sectors like aerospace, automotive, and industrial control. These platforms offer high performance, certifications (e.g., ISO 26262, DO-178C), and technical support but at a high cost.
✅ Pros of VxWorks and QNX:
- Highly reliable with decades of deployment history
- Available safety certifications for regulated industries
- Real-time performance tuned for mission-critical systems
❌ Cons of VxWorks and QNX:
- Expensive licensing and support costs
- Closed-source, lack of transparency, or modifiability
- Limited community resources
- May lock you into proprietary ecosystems
Where Zephyr Wins:
Zephyr is open source, cost-effective, and rapidly maturing. While it may not replace commercial RTOSes in high-assurance safety environments (yet), it’s more than adequate for many IoT, wearable, and industrial applications.
Zephyr gives you:
- Source-level visibility
- Customizable kernel and modules
- A robust community and professional-grade features
For startups, research, or product lines that don’t require formal certifications, Zephyr is an excellent alternative to expensive commercial RTOS platforms.
Making the Decision: When to Choose Zephyr
Choose Zephyr if:
- You’re ready to move beyond Arduino and bare metal
- You want cross-platform application code and drivers that can be easily ported to different architectures
- You need a scalable platform for real-world IoT deployments
- You want to take advantage of modular drivers, BLE, Wi-Fi, graphics, and filesystems
- You need a consistent build system and modern dev tools
- You want long-term support, strong documentation, and a vibrant developer ecosystem
Skip Zephyr if:
- You’re working with ultra-constrained devices where every byte matters
- Your application is truly simple and doesn’t need an RTOS (i.e. a superloop will suffice)
- You’re in a regulated industry that mandates certified RTOS platforms (unless you plan to certify Zephyr yourself)
Learn Zephyr with Hands-On Training
The best way to evaluate Zephyr is to try it. I’ve created a detailed 12-part video series on Zephyr that walks you through:
- Setting up the environment
- Building your first Zephyr application
- Using CMake, Kconfig, Devicetree, and debugging tools
- Writing fully abstracted device drivers
- Working with popular libraries for WiFi and graphics (LVGL)
- Creating a custom board support package
👉 Check out the full Zephyr video series on DigiKey’s channel
This series is practical, step-by-step, and designed to help you skill up quickly with Zephyr.
Final Thoughts
Zephyr is more than just an RTOS. It’s an embedded development ecosystem that matches the complexity and scale of modern IoT projects. Whether you’re moving beyond Arduino or replacing a patchwork of open-source libraries, Zephyr offers a unified, production-ready platform for the next generation of embedded programming.
It gives you what bare-metal can’t, what Arduino doesn’t, what FreeRTOS leaves out, and what commercial RTOS platforms make you pay for.
If you’re serious about building secure, scalable, and maintainable electronics solutions, Zephyr is worth your time.
Happy hacking!
Great comparison, and it all looks like I agree. But, gotta say, thank goodness for Arduino (& circutpython). It got me started learning this wonderful stuff.
Completely agree. I still use Arduino and CircuitPython for quick projects and prototypes!