Introduction and configuration

nrfx is a standalone set of drivers for peripherals present in Nordic Semiconductor’s SoCs. It originated as an extract from the nRF5 SDK. The intention was to provide drivers that can be used in various environments without the necessity to integrate other parts of the SDK into them. For the user’s convenience, the drivers come with the MDK package. This package contains definitions of register structures and bitfields for all supported SoCs, as well as startup and initialization files for them.

Refer to the Driver support overview to check which drivers are suitable for a given SoC.

Integration

The purpose of nrfx is to make it possible to use the same set of peripheral drivers in various environments, from RTOSes to bare metal applications. Hence, for a given host environment, a light integration layer must be provided that implements certain specific routines, like interrupt management, critical sections, assertions, or logging. This is done by filling a predefined set of macros with proper implementations (or keeping some empty if desired) in files named:

Templates of these files are provided in the templates subfolder. Their customized versions can be placed in any location within the host environment that the used compiler can access via include paths.

In addition, the following locations should be specified as include paths ([nrfx] stands for the nrfx root folder location): 

[nrfx]/
[nrfx]/drivers/include
[nrfx]/mdk

Note

Unless otherwise stated, nrfx API functions do not provide thread safety themselves. Users are responsible for providing the proper synchronization of the nrfx function calls in a given environment if those are to be used from different contexts.

IRQ handlers

The IRQ handlers in all drivers are implemented as ordinary API functions named “nrfx_*_irq_handler”. They can be bound to some structures or called in a specific way according to the requirements of the host environment. To install the handlers in the standard MDK way, you must only add the following line to the nrfx_glue.h file:

#include <soc/nrfx_irqs.h>

This will cause the preprocessor to properly rename all the IRQ handler functions so that the linker could install them in the vector table.

Configuration

The drivers use both dynamic (run time) and static (compile time) configuration.

Dynamic configuration is done by specifying desired options in configuration structures passed to the drivers during their initialization. Refer to the API reference for a given driver to see the members of its configuration structure.

Static configuration allows enabling and disabling (excluding their code from compilation) particular drivers or in some cases their specific features, defining default parameters for dynamic configuration, parametrization of logging in particular drivers. It is done by specifying desired values of macros in a file named:

  • nrfx_config.h

This file, similarly to the integration files mentioned above, can be placed in any suitable location within the host environment. The templates subfolder contains templates of configuration files for all currently supported Nordic SoCs. These files are included through a common nrfx_config.h file, according to the selected SoC. Refer to the “driver configuration” section in the API reference for a given driver for more information regarding configuration options available for it.

Additional requirements

Nordic SoCs are based on ARM® Cortex™-M series processors. Before you can start developing with nrfx, you must add the CMSIS header files to include paths during the compilation process. Download these files from the following website: