Zephyr RTOS
Zephyr is an open-source Real-Time Operating System (RTOS) hosted by the Linux Foundation, designed for resource-constrained embedded devices. It has rapidly become the RTOS of choice for modern IoT development — particularly on Nordic Semiconductor and STM32 platforms — thanks to its comprehensive networking stacks, security features, and vendor-neutral governance.
Why Zephyr Is Winning
In 2024, the Zephyr Project reached 1,100 unique contributors (50%+ first-time), surpassed 100,000 commits, and added support for 150 new boards. Nordic Semiconductor’s official SDK (nRF Connect SDK) is built entirely on Zephyr.
| Metric | Value (2024) |
|---|---|
| Contributors | 1,100+ unique (50% first-time) |
| Total commits | 100,000+ |
| Supported boards | 450+ |
| Supported architectures | ARM Cortex-M/A/R, RISC-V, x86, ARC, MIPS, Xtensa, SPARC |
| License | Apache 2.0 |
| Governance | Linux Foundation (vendor-neutral) |
Key Features
- Built-in networking — BLE 5.4, Thread 1.3, Wi-Fi, LoRaWAN, LwM2M, CoAP, MQTT, TCP/IP, WebSocket
- Security — MCUboot integration, PSA Certified, Trusted Firmware-M (TF-M), mbedTLS
- Device drivers — Unified driver model for SPI, I²C, UART, ADC, PWM, GPIO, sensors, displays
- Power management — Tickless kernel, device PM framework, system power states
- Build system — CMake + west (meta-tool), Kconfig for configuration, Devicetree for hardware abstraction
- Testing — Twister test framework, QEMU/native_sim for CI/CD without hardware
Zephyr vs. FreeRTOS
| Factor | Zephyr | FreeRTOS |
|---|---|---|
| Scope | Full RTOS + drivers + networking + security | Kernel only (no drivers, no networking built-in) |
| RAM footprint | 8–64 KB (configurable) | 4–10 KB (kernel only) |
| Flash footprint | 32–256 KB | 6–12 KB (kernel only) |
| BLE stack | Built-in (host + controller) | External (NimBLE or vendor SDK) |
| Thread/Matter | Built-in | Not available |
| Secure boot | MCUboot integrated | Manual integration |
| Build system | CMake + west + Kconfig + Devicetree | Vendor IDE or CMake |
| Learning curve | Steeper (powerful but complex) | Easier (minimalist) |
| Best for | Complex IoT products, multi-protocol | Simple single-task, RTOS kernel only |
Top Contributing Companies (2024)
- Nordic Semiconductor
- Intel
- NXP
- STMicroelectronics
- Renesas
- Espressif
Related Terms
- RTOS — Zephyr is a specific implementation of a Real-Time Operating System.
- BLE — Zephyr includes a complete BLE 5.4 host and controller stack.
- MCUboot — The secure bootloader integrated by default with Zephyr.
- RISC-V — Zephyr has extensive RISC-V support, enabling vendor-independent embedded development.
Zephyr is our primary RTOS for Nordic nRF and STM32 development. From bare-metal to multi-protocol IoT devices. See our Embedded Systems Development services.