Dynamic switching between native TX power and nRF21540 FEM on nRF54L15

RE: Dynamic switching between native TX power and nRF21540 FEM on nRF54L15

Simonr — Mon, 30 Mar 2026 11:58:15 GMT

Yes, this should be possible, but you will need a physical RF switch, as there is no API for doing this. You will need to "fool" the MPSL to output 8dBm while it thinks the FEM is still connected I think, or you can use GPIO only mode.

Best regards,

Simon

RE: Dynamic switching between native TX power and nRF21540 FEM on nRF54L15

Ziyao Zhou — Fri, 27 Mar 2026 15:02:38 GMT

Thank you for your reply!

So that means there is no way to switch between MPSL on and MPSL off.

In my application, I need to dynamically adjust the transmit power in the range of 0 dBm to 20 dBm. To optimize overall power consumption, my plan is to use the native radio TX power for levels below 8 dBm, and switch to the FEM for higher output power above 8 dBm. I intend to implement this using an RF switch architecture similar to the one used on the nRF7002 DK. Is there any way to do such application?

RE: Dynamic switching between native TX power and nRF21540 FEM on nRF54L15

Simonr — Fri, 27 Mar 2026 13:55:29 GMT

The FEM layer of the MPSL does a lot of this work for you, so you don't need to worry about a lot of this. Please go through the documentation here for details. https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/app_dev/device_guides/fem/index.html

The MPSL is a build time setting, so this is not configurable during runtime as far as I know. https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/app_dev/device_guides/fem/fem_mpsl_fem_only.html

Best regards,

Simon