How could I use the FEM with nRF54LM20 DK?

[Ziyao Zhou]

Hi

I want to use the FEM 21540 with nRF54LM20.

My overlay is :

#include <zephyr/dt-bindings/gpio/gpio.h>

/*
 * nRF54LM20B DK cpuapp overlay - BLE Central + USB UVC
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */

&uicr {
	nfct-pins-as-gpios;
};

&dppic10 { status = "okay"; };
&ppib11  { status = "okay"; };
&ppib21  { status = "okay"; };
&dppic20 { status = "okay"; };
&ppib22  { status = "okay"; };
&ppib30  { status = "okay"; };
&dppic30 { status = "okay"; };

/ {
	chosen {
		nordic,nus-uart = &uart20;
		zephyr,camera = &shm_cam0;
	};

	uvc: uvc {
		compatible = "zephyr,uvc-device";
	};

	shm_cam0: shm-camera {
		compatible = "app,shm-video";
	};

	nrf_radio_fem: nrf21540-fem {
		compatible = "nordic,nrf21540-fem";
		tx-en-gpios = <&gpio1 11 GPIO_ACTIVE_HIGH>;
		rx-en-gpios = <&gpio1 12 GPIO_ACTIVE_HIGH>;
		pdn-gpios = <&gpio1 2 GPIO_ACTIVE_HIGH>;
		mode-gpios = <&gpio1 3 GPIO_ACTIVE_HIGH>;
		tx-en-settle-time-us = <27>;
		rx-en-settle-time-us = <12>;
	};
};

&uart20 {
	pinctrl-0 = <&uart20_nohwfc_default>;
	pinctrl-1 = <&uart20_nohwfc_sleep>;
	pinctrl-names = "default", "sleep";
};

&pinctrl {
	uart20_nohwfc_default: uart20_nohwfc_default {
		group1 {
			psels = <NRF_PSEL(UART_TX, 1, 16)>,
				<NRF_PSEL(UART_RX, 1, 17)>;
			bias-pull-up;
		};
	};

	uart20_nohwfc_sleep: uart20_nohwfc_sleep {
		group1 {
			psels = <NRF_PSEL(UART_TX, 1, 16)>,
				<NRF_PSEL(UART_RX, 1, 17)>;
			low-power-enable;
		};
	};
};

zephyr_udc0: &usbhs {
	status = "okay";
};

My config is:

# nRF21540 FEM / PA-LNA
CONFIG_MPSL=y
CONFIG_MPSL_FEM=y
CONFIG_MPSL_FEM_NRF21540_GPIO=y
CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=20
CONFIG_MPSL_FEM_NRF21540_RX_GAIN_DB=13
CONFIG_MPSL_FEM_NRF21540_RUNTIME_PA_GAIN_CONTROL=y

I think this should work because my nRF54L15 DK works well with this. 

But it is not working, could you give me some advice?

[Ziyao Zhou]

I have checked the official application notes, notice that 54LM20 support FEM SPI mode. 

But I have no idea which pin should I use. So I try to add the argument: 

-DSHIELD=nrf21540ek

But after buiding I cannot see any change in the DTS file indicating what pin should I use. 

Could you give me some advice?