Introduction

The nRF Connect SDK is a scalable and unified software development kit for building low-power wireless applications based on the Nordic Semiconductor nRF52, nRF53, and nRF91 Series wireless devices. It offers an extensible framework for building size-optimized software for memory-constrained devices as well as powerful and complex software for more advanced devices and applications.

It integrates the Zephyr™ real-time operating system (RTOS) and a wide range of complete applications, samples, and protocol stacks such as Bluetooth® Low Energy, Bluetooth mesh, Matter, Thread/Zigbee and LTE-M/NB-IoT/GPS, TCP/IP. It also includes middleware such as CoAP, MQTT, LwM2M, various libraries, hardware drivers, Trusted Firmware-M for security, and a secure bootloader (MCUboot).

Repositories

The nRF Connect SDK is a combination of software developed by Nordic Semiconductor and open source projects, hosted as Git repositories in the nrfconnect GitHub organization.

The sdk-nrf repository is the manifest repository. It contains the SDK’s west manifest file that lists all the SDK’s repositories and their revisions. This code base is managed with the West tool.

Some notable repositories include:

  • sdk-nrf repository - Contains applications, samples, libraries, and drivers that are specifically targeted at Nordic Semiconductor devices.

  • sdk-nrfxlib repository - Contains closed-source libraries and modules in binary format. See the nrfxlib documentation.

  • sdk-zephyr repository - Contains a fork of the Zephyr project, which provides samples, libraries, and drivers for a wide variety of devices, including Nordic Semiconductor devices. See the documentation in Nordic Semiconductor’s Zephyr fork.

    Note

    The sdk-zephyr repository is a soft fork that Nordic Semiconductor maintains. It is not the same as Zephyr SDK, which is a set of installation tools used while installing the nRF Connect SDK.

  • sdk-mcuboot repository - Contains a fork of the MCUboot project, which provides a secure bootloader application. You can find the fork in bootloader/mcuboot after obtaining the nRF Connect SDK source code. See the documentation in Nordic Semiconductor’s MCUboot fork.

All repositories with the prefix sdk contain the nRF Connect SDK firmware and code. Every nRF Connect SDK release consists of a combination of all included repositories at different revisions. See the nRF Connect SDK repository revisions section for a comprehensive list of repositories and their current revisions. The revision of each of those repositories is determined by the current revision of the main (manifest) repository sdk-nrf.

Versions and revisions

The nRF Connect SDK uses a versioning scheme similar to Semantic versioning, but with important semantic differences. Every release of the nRF Connect SDK is identified with a version string, in the format MAJOR.MINOR.PATCH. The version numbers are incremented based on the following criteria:

  • The MAJOR version number is increased seldom, whenever a release is deemed to be introducing a large number of substantial changes across the board.

  • The MINOR version number is increased every time a major release is cut. Major releases are the default types of an nRF Connect SDK release. They introduce new functionality and may break APIs.

  • The PATCH version number is increased whenever a minor or bugfix release is cut. Minor releases only address functional issues but do not introduce new functionality.

In between releases, nRF Connect SDK is not static. Instead, it changes its revision every time a Git commit is merged into the sdk-nrf repository. The revision of the SDK is considered to be equivalent to the repository revision of sdk-nrf, because it is the manifest repository. This means that, by virtue of containing the west manifest file, its revision uniquely identifies the revisions of all other repositories included in the SDK.

A special value of 99 for the PATCH version number indicates that the version string does not belong to a release, but rather a point in between two major releases. For example, 2.2.99 indicates that this particular revision of the nRF Connect SDK is somewhere between versions 2.2.0 and 2.3.0.

Revisions can either be Git SHAs or tags, depending on whether the current revision is associated with a release (in which case it is a tag) or is just any revision in between releases.

For a more formal description of versions and revisions, see Revisions.

Tools and configuration

The figure below visualizes the tools and configuration methods in the nRF Connect SDK. They are based on the Zephyr project. All of them have a role in the creation of an application, from configuring the libraries or applications to building them.

nRF Connect SDK tools and configuration

nRF Connect SDK tools and configuration methods

Git

Git is a free and open source distributed version control system that allows managing the changes in the code or other collections of information (set of files) over time.

Git offers a lot of flexibility in how users manage changes, and repositories are easily duplicated. In nRF Connect SDK, forking is the agreed-upon Git workflow. To contribute, the official public repository in GitHub is forked.

A fork can be hosted on any server, including a public Git hosting site like GitHub. It is, however, important to differentiate between the generic concept of a fork and GitHub’s concept of a GitHub fork. When you create a GitHub fork, GitHub copies the original repository and tags the downstream repository (the fork) with a flag that allows users to send pull requests from the fork to its upstream repository. GitHub also supports creating forks without linking them to the upstream repository. See the GitHub documentation for information about how to do this.

West

The Zephyr project includes a tool called west. The nRF Connect SDK uses west to manage the combination of multiple Git repositories and versions.

Some of west’s features are similar to those provided by submodules of Git and Google’s Repo tool. But west also includes custom features required by the Zephyr project that were not sufficiently supported by the existing tools.

West’s workspace contains exactly one manifest repository, which is a main Git repository containing a west manifest file. Additional Git repositories in the workspace managed by west are called projects. The manifest repository controls which commits to use from the different projects through the manifest file. In the nRF Connect SDK, the main repository sdk-nrf contains a west manifest file west.yml, that determines the revision of all other repositories. This means that sdk-nrf acts as the manifest repository, while the other repositories are projects.

When developing in the nRF Connect SDK, your application will use libraries and features from folders that are cloned from different repositories or projects. The west tool keeps control of which commits to use from the different projects. It also makes it fairly simple to add and remove modules.

See Getting started for information about how to install the nRF Connect SDK and about the first steps. See Development model for more information about the nRF Connect SDK code base and how to manage it.

Applications

To start developing your application you need to understand a few fundamental concepts. Follow the Zephyr guide to Application Development and browse through the included reference applications in the nRF Connect SDK to get familiar with the basics.

You also need to decide how to structure your application. You can choose from a few alternative user workflows, but having the application as the manifest repository is recommended. An ncs-example-application repository is provided to serve as a reference or starting point.

Licenses

Licenses are located close to the source files. You can find a LICENSE file, containing the details of the license, at the top of every nRF Connect SDK repository. Each file included in the repositories also has an SPDX identifier that mentions this license.

If a folder or set of files is open source and included in nRF Connect SDK under its own license (for example, any of the Apache or MIT licenses), it will have either its own LICENSE file included in the folder or the license information embedded inside the source files themselves.

You can use the west ncs-sbom utility to generate a license report. It allows you to generate a report for the nRF Connect SDK, built application, or specific files. The tool is highly configurable. It uses several detection methods, such as:

  • Search based on SPDX tags.

  • Search license information in files.

  • The Scancode-Toolkit.

Depending on your configuration, the report is generated in HTML or SPDX, or in both formats. See the Software Bill of Materials documentation for more information.

Documentation pages

The documentation consists of several inter-linked documentation sets, one for each repository.

The entry point is the nRF Connect SDK documentation that you are currently reading. The local Zephyr documentation is a slightly extended version of the official Zephyr Project documentation, containing some additions specific to Nordic Semiconductor. The local MCUboot documentation is a slightly extended version of the official MCUboot documentation, containing some additions specific to Nordic Semiconductor.

You can switch between these documentation sets by using the navigation bar at the top of the page.

To access different versions of the nRF Connect SDK documentation, use the version drop-down in the top right corner. A “99” at the end of the version number of this documentation indicates continuous updates on the main branch since the previous major.minor release.

The nRF Connect SDK documentation contains all information that is specific to the nRF Connect SDK and describes our libraries, samples, and applications. API documentation is extracted from the source code and included with the library documentation.

For instructions about building the documentation locally, see Building the nRF Connect SDK documentation. For more information about the documentation conventions and templates, see About this documentation.

nRF Connect SDK repository revisions

The following table lists all the repositories (and their respective revisions) that are included as part of nRF Connect SDK 2.2.99 release:

Project

Revision

zephyr

336c245949839b1d8b01c297d821101c939265ec

nrfxlib

fc6e4b57f76bb945b9a0aede55858b196d36b609

mcuboot

4f775a87611a084a2f6ad9a8a5034e080ddcc579

trusted-firmware-m

81e6a7fbbc972b95affc9b6805b62237d0ffd6f4

find-my

8ebcde08dcc808d6f632bb5cb3e330161a4dffcd

homekit

a8a4b468abca2514f902d47ce4d7cde56e9fe762

matter

515c7c67c59cbe1b3b97b235f8c93e63131dee7a

nrf-802154

v2.2.0

mbedtls

v3.1.0-ncs2

memfault-firmware-sdk

0.35.0

sdk-hostap

7856cabe59a96466cafd27cad7e2fed0bb18cfc5

cjson

c6af068b7f05207b28d68880740e4b9ec1e4b50a

azure-sdk-for-c

308c171cb4b5eed266649012a68406487ec81fb2

cmock

f65066f15d8248e6dcb778efb8739904a4512087

cirrus

9f6b3812237fbb0d4157ba3584c13f1644fcbe3a

openthread

25506997f286fdbfa72725f4cee78c922c896255

ant

8f6e2b0470d11b5c1a97c92df35eb1350e84c5f8

canopennode

53d3415c14d60f8f4bfca54bfbc5d5a667d7e724

chre

fe0ab36e0fa7453a4c9b97bedac89709f45cf965

cmsis

74981bf893e8b10931464b9945e2143d99a3f0a3

edtt

000fb87261beaf33f80a8868e73857bd62edc668

fatfs

38f303ad09fdd687ee066a938f65ad708dd5989d

hal_nordic

fe0be3c3546e136a67264084c0e3edfd7354645a

hal_st

cccbc24c14decfd3f93959f7b14514536af973c7

hal_wurthelektronik

24ca9873c3d608fad1fea0431836bc8f144c132e

libmetal

efa2ace6028290ddee494a78ade772a0b112ab83

liblc3

448f3de31f49a838988a162ef1e23a89ddf2d2ed

littlefs

ca583fd297ceb48bced3c2548600dc615d67af24

loramac-node

ce57712f3e426bbbb13acaec97b45369f716f43a

lvgl

5ab83099854719ed326b6ecb9b09b07b1eee4818

lz4

8e303c264fc21c2116dc612658003a22e933124d

mipi-sys-t

0d521d8055f3b2b4842f728b0365d3f0ece9c37f

nanopb

dc4deed54fd4c7e1935e3b6387eedf21bb45dc38

net-tools

e0828aa9629b533644dc96ff6d1295c939bd713c

nrf_hw_models

65bc5305d432c08e24a3f343006d1e7deaff4908

open-amp

aedcc262f93bbb1b0c2f58026911575729b7465c

picolibc

04ada5951cbaf8e7b17f8226ce31cb6837c28ba7

segger

d4e568a920b4bd087886170a5624c167b2d0665e

tinycbor

9e1f34bc08123aaad7666d3652aaa839e8178b3b

tinycrypt

3e9a49d2672ec01435ffbf0d788db6d95ef28de0

TraceRecorderSource

d92607521335eaaaedb01b241cdd26fda48a5ca6

tf-m-tests

bcb53bccccdc05c713aade707e7a8ddad35c210f

psa-arch-tests

f4fc2442b8e29e2a03d9899e46e5a3ea3df8c2c9

uoscore-uedhoc

e8920192b66db4f909eb9cd3f155d5245c1ae825

zcbor

0.6.0

zscilib

ca070ddabdaf67175a2da901d0bd62e8899371c5