https://devzone.nordicsemi.com/f/nordic-q-a/111888/gpio-pins-to-control-nrf21540-femHi, I have a custom board with a nRF52840 and the nRF21540 FEM. To control my FEM, I have added the following to my code to my nRF52840_nRF52840.dts file: / { nrf_radio_fem: name_of_fem_node { compatible = &quot;nordic,nrf21540-fem&quot; ; tx-en-gpiosen-USTelligent Community 13Mon, 10 Jun 2024 15:35:12 GMThttps://devzone.nordicsemi.com/thread/488171?ContentTypeID=1Mon, 10 Jun 2024 15:35:12 GMT137ad170-7792-4731-bb38-c0d22fbe4515:83d24008-79cf-4615-bc7f-5fb39cd1a8f6Naeem Maroof<p>Hi,</p> <p>To use radio protocols and a FEM with your application, you need to enable Front-end module feature in the Multiprotocol Service Layer (MPSL) library. Using MPSL supports SPI/GPIO mode or the GPIO only mode.</p> <p><a href="https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.5.2/nrf/device_guides/working_with_fem.html#enabling-fem-and-mpsl">Enabling FEM and MPSL</a>&nbsp;Adding support for MPSL (Enable MPSL CONFIG_MPSL,&nbsp;Enable FEM CONFIG_MPSL_FEM, choose FEM Implementation CONFIG_MPSL_FEM_NRF21540_GPIO)</p> <p>The (MPSL) library provides multiprotocol support, but you can also use it in applications that require only one protocol. To avoid conflicts, check the protocol documentation to see if the protocol uses the FEM support provided by MPSL.</p> <p><a href="https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/mpsl/doc/api.html">MPSL API Documentation</a></p> <p><a href="https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.6.1/nrf/device_guides/working_with_fem.html#:~:text=The%20following%20test%20samples%20support%20FEM%20control%3A">Samples supporting FEM Control</a></p><div style="clear:both;"></div>