What is the proper way to conditionally build?

[mej7000]

I am building (v2.5.0) for both the nrf52840dk and the nrf21540dk.

1. west build -b nrf21540dk_nrf52840 -d build21540
2. west build -b nrf52840dk_nrf52840 -d build52840

so I only want the following to compile with the nrf21540 build.

#FEM NRF21540

# CONFIG_MPSL_FEM_DEVICE_CONFIG_254=y

# CONFIG_MPSL_FEM_NRF21540_GPIO=y

# CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=20

# CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=20

# CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB=10

Rather than commenting them out, what is the proper way to conditionally build based on the selected processor/dk board?

[Maria Gilje]

Hello,

The proper way is to create a board-specific configuration in <your-project-directory>/boards which you name nrf21540dk_nrf52840.conf. Put the Kconfig symbols you only want for the nRF21540 DK build there. The build system will interpret the extra configuration file as a fragment which is added to the main configuration file (i.e. prj.conf).

See also this documentation for general information on different configuration files: https://docs.nordicsemi.com/bundle/ncs-2.5.0/page/nrf/config_and_build/multi_image.html#permanent_configuration_changes_to_child_images

Best regards,

Maria

[mej7000]

Thanks! That makes perfect sense.

To reiterate: nrf21540dk_nrf52840.conf will be combined with prj.conf when west build -b nrf21540dk_nrf52840 -d build21540 is executed (and obviously not combined when west build -b nrf52840dk_nrf52840 -d build52840 is executed.)

nrf21540dk_nrf52840.conf