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Board definition

v3.0.0
v2.9.0 – v2.7.0
v2.6.2 – v2.5.2

v3.0.0

Note

This lesson covers how to define boards in the nRF Connect SDK using both hardware models v1 and v2 (HWMv1 and HWMv2 respectively).

This exercise tab covers nRF Connect SDK where HWMv2 is used, which is recommended for all new designs.

When developing applications with nRF Connect SDK, the concept of a board is really at the center of the development. Built on the Zephyr RTOS, the nRF Connect SDK emphasizes portability, making it easier to develop applications that can run across different hardware platforms.

What is a board?

In this context, a board refers to the specific hardware platform you are targeting – whether it’s a Nordic development kit or your own custom PCB. The board abstraction allows you to port your application from one platform to another with minimal changes. For example, you can transition an application from the nRF52840 DK to the nRF54L15 DK – or even to a custom board, relatively easily.

Unlike traditional embedded development, where hardware is defined in C header files, the nRF Connect SDK uses devicetree and Kconfig to decouple hardware configuration from application code.

Board structure in nRF Connect SDK

In the context of the nRF Connect SDK and Zephyr, a board is essentially a folder containing a set of configuration and metadata files that describe your hardware.

This includes:

Devicetree files – Describes the hardware, including SoC(s), peripheral configurations, etc.
Kconfig files – Specifies software configuration options needed for your board.
YAML (.yml) files – Contains metadata such as board names, SoC(s), revisions and variants.
Optional C files – Includes special initialization procedures required for your hardware.
Optional documentation – Provides board-specific documentation.

These components together form the board definition, which specifies:

SoC configuration – The exact SoC(s) used (e.g., nRF54L15 QFAA), clock frequencies, memory configurations, and other hardware-specific details.
Peripheral configuration – Settings for UART, SPI, I2C, GPIO, and other peripherals.
Memory configuration – Flash/RAM sizes and memory partitioning used for application, internal storage, bootloader, and other software components.
Pin mapping – Mapping between pins and their corresponding functions (SoCs have multiple pins that can be configured for different functions, e.g., GPIO, UART, SPI.
Clock and interrupt configuration – Ensures accurate timing across the system.
Driver configuration – Defines parameters for hardware drivers, like transport settings, clock settings, etc.
Special initialization routines – Handles unique board requirements, such as configuring special bootloader configuration, hardware muxes configuration, or special PMIC features.

While this may sound intimidating, the SDK already provides most configurations—particularly for the CPU, SoC, and architecture.

Hardware support hierarchy (HWMv2)

nRF Connect SDK uses the same hardware support hierarchy as Zephyr, which is divided into layers, organized from most to least specific. The hierarchy starts with the most specific layer, the board, and moves towards more general layers such as SoC, SoC series, SoC family, CPU core, and finally architecture.

Board – A specific hardware specification with SoC(s) and peripherals
SoC – The exact System on Chip(s), the board’s CPU is a part of (Provided by nRF Connect SDK/Zephyr)
SoC family – A broad group of similar SoCs (Provided by nRF Connect SDK/Zephyr)
SoC series – A smaller subset of tightly related SoCs (Provided by nRF Connect SDK/Zephyr)
CPU – The CPU in an architecture (Provided by nRF Connect SDK/Zephyr)
Architecture – The instruction set architecture (Provided by nRF Connect SDK/Zephyr)

Starting with nRF Connect SDK v2.7.0, the Hardware Model v2 (HWMv2) is now the default system for board definitions. It replaces the older HWMv1 system, which struggled with modern hardware setups involving multiple SoCs, cores, or architectures.

Why HWMv2?

HWMv1 was designed for single-target boards (one SoC, one CPU), which made it inadequate for multi-core or multi-SoC systems.

Therefore, HWMv2 was born as an improved and extensible system for defining boards both in nRF Connect SDK and upstream Zephyr.

With HWMv2, boards, are no longer located under architecture, but rather under their vendor. The reasoning is that a single board can have multiple architectures.

HWMv2 offers reusability in Sysbuild, which means you can select to generate extra images for things like MCUboot or network cores in a more coupled way.

There is a new common description format for everything from the boards, SoCs, families, series, architectures, CPU clusters, variants, and revisions. The new common description is YAML-based (.yml or .yaml), which we will dive into in the next topic. This lays the foundation for a flexible and extensible system for defining boards.

To understand these layers in HWMv2, consider the nRF9160 DK, which contains two SoCs:

nRF9160 (part of the nRF91 Series, Cortex-M33)
nRF52840 (part of the nRF52 Series, Cortex-M4)

The board files for your custom board (in the light blue box) are what you need to write yourself, while the dark blue boxes are provided by the SDK.

The architecture of Nordic SoCs will either be ARM or RISC-V for the co-processors on the nRF54 Series.

Let’s take a look at some more examples of Nordic development kits:

Board	SoC	SoC family	SoC series	CPU	Architecture
`nrf52833dk`	nRF52833 or nRF52820 (through emulation)	Nordic nRF	nRF52	Arm Cortex-M4	Arm
`nrf54l15dk`	nRF54L15	Nordic nRF	nRF54L	Arm Cortex-M33 & Nordic VPR	Arm & RISC-V
`nrf5340dk`	nRF5340	Nordic nRF	nRF53	Arm Cortex-M33	Arm

A note on drivers

While board files define internal SoC hardware, drivers are required for external components, like sensors. Drivers are declared via the compatible property in the devicetree. Drivers do not reside in the board folder, but rather, they have dedicated locations within the nRF Connect SDK (nrf/drivers/sensor) and Zephyr (zephyr/drivers/sensor).

The nRF Connect SDK already includes a rich collection of drivers. Examples of boards with external sensors include micro:bit v2, Thingy:53, Thingy:91, and Thingy:91 X.

More on this

If your custom hardware uses a component without an existing driver, you will need to implement one. We will take a look at how to create your own custom driver in Lesson 7 – Device driver development.

v2.9.0 – v2.7.0

Note

This lesson covers how to define boards in the nRF Connect SDK using both hardware models v1 and v2 (HWMv1 and HWMv2 respectively).

This exercise tab covers nRF Connect SDK where HWMv2 is used, which is recommended for all new designs.

What is a board?

Unlike traditional embedded development, where hardware is defined in C header files, the nRF Connect SDK uses devicetree and Kconfig to decouple hardware configuration from application code.

Board structure in nRF Connect SDK

In the context of the nRF Connect SDK and Zephyr, a board is essentially a folder containing a set of configuration and metadata file that describe your hardware.

This includes:

Devicetree files – Describes the hardware, including SoC(s), peripheral configurations, etc.
Kconfig files – Specifies software configuration options needed for your board.
YAML (.yml) files – Contains metadata such as board names, SoC(s), revisions and variants.
Optional C files – Includes special initialization procedures required for your hardware.
Optional documentation – Provides board-specific documentation.

These components together form the board definition, which specifies:

SoC configuration – The exact SoC(s) used (e.g., nRF54L15 QFAA), clock frequencies, memory configurations, and other hardware-specific details.
Peripheral configuration – Settings for UART, SPI, I2C, GPIO, and other peripherals.
Memory configuration – Flash/RAM sizes and memory partitioning used for application, internal storage, bootloader, and other software components.
Pin mapping – Mapping between pins and their corresponding functions (SoCs have multiple pins that can be configured for different functions, e.g., GPIO, UART, SPI.
Clock and interrupt configuration – Ensures accurate timing across the system.
Driver configuration – Defines parameters for hardware drivers, like transport settings, clock settings, etc.
Special initialization routines – Handles unique board requirements, such as configuring special bootloader configuration, hardware muxes configuration, or special PMIC features.

While this may sound intimidating, the SDK already provides most configurations—particularly for the CPU, SoC, and architecture.

Hardware support hierarchy (HWMv2)

Board – A specific hardware specification with SoC(s) and peripherals
SoC – The exact System on Chip(s), the board’s CPU is a part of (Provided by nRF Connect SDK/Zephyr)
SoC family – A broad group of similar SoCs (Provided by nRF Connect SDK/Zephyr)
SoC series – A smaller subset of tightly related SoCs (Provided by nRF Connect SDK/Zephyr)
CPU – The CPU in an architecture (Provided by nRF Connect SDK/Zephyr)
Architecture – The instruction set architecture (Provided by nRF Connect SDK/Zephyr)

Why HWMv2?

HWMv1 was designed for single-target boards (one SoC, one CPU), which made it inadequate for multi-core or multi-SoC systems.

Therefore, HWMv2 was born as an improved and extensible system for defining boards both in nRF Connect SDK and upstream Zephyr.

With HWMv2, boards, are no longer located under architecture, but rather under their vendor. The reasoning is that a single board can have multiple architectures.

HWMv2 offers reusability in Sysbuild, which means you can select to generate extra images for things like MCUboot or network cores in a more coupled way.

To understand these layers in HWMv2, consider the nRF9160 DK, which contains two SoCs:

nRF9160 (part of the nRF91 Series, Cortex-M33)
nRF52840 (part of the nRF52 Series, Cortex-M4)

The board files for your custom board (in the light blue box) are what you need to write yourself, while the dark blue boxes are provided by the SDK.

The architecture of Nordic SoCs will either be ARM or RISC-V for the co-processors on the nRF54 Series.

Let’s take a look at some more examples of Nordic development kits:

Board	SoC	SoC family	SoC series	CPU	Architecture
`nrf52833dk`	nRF52833 or nRF52820 (through emulation)	Nordic nRF	nRF52	Arm Cortex-M4	Arm
`nrf54l15dk`	nRF54L15	Nordic nRF	nRF54L	Arm Cortex-M33 & Nordic VPR	Arm & RISC-V
`nrf5340dk`	nRF5340	Nordic nRF	nRF53	Arm Cortex-M33	Arm

A note on drivers

The nRF Connect SDK already includes a rich collection of drivers. Examples of boards with external sensors include micro:bit v2, Thingy:53, Thingy:91, and Thingy:91 X.

More on this

v2.6.2 – v2.5.2

Important

This lesson covers how to define boards in the nRF Connect SDK using both hardware models v1 and v2 (HWMv1 and HWMv2 respectively).

This exercise tab is for nRF Connect SDK v2.6.2 – v2.5.2, where HWMv1 is used. HWMv1 is deprecated and removed in nRF Connect SDK v3.0.0. We recommend using HWMv2 for all new designs (other tabs).

Either watch the video or read the text below the video:

What is a board?

In this context, a board refers to the specific hardware platform you are targeting – whether it’s a Nordic development kit or your own custom PCB. The board abstraction allows you to port your application from one platform to another with minimal changes. For example, you can transition an application from the nRF52840 DK to the nRF5340 DK – or even to a custom board, relatively easily.

Unlike traditional embedded development, where hardware is defined in C header files, the nRF Connect SDK uses devicetree and Kconfig to decouple hardware configuration from application code.

Board structure in nRF Connect SDK

In the context of the nRF Connect SDK and Zephyr, a board is essentially a folder containing a set of configuration and metadata file that describe your hardware.

This includes:

Devicetree files – Describes the hardware, including SoC(s), peripheral configurations, etc.
Kconfig files – Specifies software configuration options needed for your board.
Optional C files – Includes special initialization procedures required for your hardware.
Optional documentation – Provides board-specific documentation.

These components together form the board definition, which specifies:

SoC configuration – The exact SoC(s) used, clock frequencies, memory configurations, and other hardware-specific details.
Peripheral configuration – Settings for UART, SPI, I2C, GPIO, and other peripherals.
Memory configuration – Flash/RAM sizes and memory partitioning used for application, internal storage, bootloader, and other software components.
Pin mapping – Mapping between pins and their corresponding functions (SoCs have multiple pins that can be configured for different functions, e.g., GPIO, UART, SPI.
Clock and interrupt configuration – Ensures accurate timing across the system.
Driver configuration – Defines parameters for hardware drivers, like transport settings, clock settings, etc.
Special initialization routines – Handles unique board requirements, such as configuring special bootloader configuration, hardware muxes configuration, or special PMIC features.

While this may sound intimidating, the SDK already provides most configurations—particularly for the CPU, SoC, and architecture.

Hardware support hierarchy (HWMv1)

Board – A specific hardware specification with SoC(s) and peripherals
SoC – The exact System on Chip(s) the board’s CPU is a part of (Provided by nRF Connect SDK/Zephyr)
SoC series – A smaller subset of tightly related SoCs (Provided by nRF Connect SDK/Zephyr)
SoC family – A broad group of similar SoCs (Provided by nRF Connect SDK/Zephyr)
CPU – The CPU in an architecture (Provided by nRF Connect SDK/Zephyr)
Architecture – The instruction set architecture (Provided by nRF Connect SDK/Zephyr)

You can visualize the hierarchy like this:

The architecture of Nordic SoCs will either be ARM or RISC-V for the co-processors on the nRF54 Series.

Let’s take a look at some more examples of Nordic development kits:

Board	SoC	SoC Series	SoC family	CPU Core	Architecture
`nrf52833dk_nrf52833`	nRF52833	nRF52	nRF5 Family	Arm Cortex-M4	Arm
`nrf5340dk_nrf5340_cpuapp`	nRF5340	nRF53	nRF5 Family	Arm Cortex-M33	Arm
`nrf9160dk_nrf9160`	nRF9160	nRF91	nRF9 Family	Arm Cortex-M33	Arm

A note on drivers

The nRF Connect SDK already includes a rich collection of drivers. Examples of boards with external sensors include micro:bit v2, Thingy:53, Thingy:91.

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nRF Connect SDK Intermediate

Board definition

Note

What is a board?

Board structure in nRF Connect SDK

Hardware support hierarchy (HWMv2)

Why HWMv2?

A note on drivers

More on this

Note

What is a board?

Board structure in nRF Connect SDK

Hardware support hierarchy (HWMv2)

Why HWMv2?

A note on drivers

More on this

Important

What is a board?

Board structure in nRF Connect SDK

Hardware support hierarchy (HWMv1)

A note on drivers

More on this