Door 12 – nRF Connect SDK: Zephyr RTOS vs Bare Metal option
nRF Connect SDK
Essential toolkit for IoT development
The nRF Connect SDK is a versatile and unified software development kit designed for creating IoT solutions using Nordic’s nRF54, nRF53, nRF52, nRF70, and nRF91 Series wireless devices. It provides a flexible framework for building secure, energy-efficient products that range from lightweight applications on resource-constrained devices to complex, feature-rich systems.
Built on the open-source Zephyr RTOS and enhanced with Nordic’s proprietary software, the SDK comes as a single, optimized package tailored to Nordic’s hardware portfolio. Out of the box, developers gain access to a wide set of resources—sample applications, protocol stacks, networking libraries, drivers, and security features—allowing them to concentrate on innovating and differentiating their products rather than reinventing the basics.
The SDK can be expanded through Add-ons, contributed by Nordic and its partners, which deliver extra functionality such as specialized applications, protocol support, or even complete SDKs for targeted technologies and use cases.
Alongside Zephyr-based development, the SDK also offers a Bare Metal option for the nRF54L Series. This path is ideal for straightforward Bluetooth Low Energy applications that don’t require an RTOS or advanced features, giving developers the freedom to choose the approach that best suits their project.
Nordic supports the SDK with a comprehensive suite of development tools—including nRF Connect for Desktop, Mobile, and VS Code—providing a full IDE environment for building next-generation IoT applications. To help developers get started quickly, Nordic also offers interactive online courses through the Nordic Developer Academy, featuring hands-on exercises across a variety of topics.
Zephyr RTOS vs Bare Metal option
Zephyr RTOS and the nRF Connect SDK Bare Metal option are two different firmware paths within the same nRF Connect SDK environment, mainly for nRF54L Series.
Zephyr RTOS
Zephyr RTOS is an open-source, real-time operating system designed specifically for secure, low-power, and connected embedded devices. It features a small-footprint kernel, making it suitable for resource-constrained systems, and is highly configurable and modular to support a wide range of applications—from simple sensors to complex IoT devices. Zephyr includes a rich ecosystem with middleware, security features, device drivers, networking stacks, and supports multiple CPU architectures. It is the foundation of Nordic Semiconductor’s nRF Connect SDK and is recognized as the de facto industry standard for embedded RTOS solutions.
Choose Zephyr RTOS if
- You need advanced Bluetooth LE features, Central role, multiprotocol (Thread, Zigbee, Matter, etc.), or ecosystem integrations.
- Your application is complex enough to benefit from multithreading, Zephyr drivers, and rich middleware.
- You want a fully scalable platform across all Nordic device families.
Bare Metal Option
The nRF Connect SDK Bare Metal option is a new, alternative development path within the nRF Connect SDK environment that enables single-threaded bare metal Bluetooth LE application development on the nRF54L Series. It is designed for developers creating simple Bluetooth LE applications, such as straightforward data exchange applications requiring connectivity (in applications like medical devices, sports wearables, trackers, or beacons), that do not benefit from an RTOS or advanced features.
Choose Bare Metal if
- You are building a simple Bluetooth LE Peripheral‑only device on nRF54L, with no need for Central role or advanced BLE features.
- You want a programming model and SoftDevice API close to the legacy nRF5 SDK.
- You care about minimal complexity and slightly lower overhead, and single‑bank DFU is attractive.
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