nrf54l15 combine with nrf21540

[joey]

HI

I am using the DTM example routine of NCS 3.2.1 and am currently testing the combination of nRF54L15 DK and nRF21540 EK. After flashing the original example routine to the nRF54L15 (with the nRF21540 not connected yet), I set the TP (Transmit Power) to 0 dBm via the DTM 3.1.0 application, and the spectrum analyzer detected an output power of approximately 0 dBm from the nRF54L15. However, after I added the nRF21540 configuration in the overlay file, the output power dropped to approximately -10 dBm(with the nRF21540 not connected yet),. Could this be caused by an incorrect configuration somewhere?

/ {

    chosen {

        ncs,dtm-uart = &uart20;

    };

    nrf_radio_fem: nrf21540_fem{

          compatible="nordic,nrf21540-fem";

          tx-en-gpios=<&gpio1 9 GPIO_ACTIVE_HIGH>;

          rx-en-gpios=<&gpio1 11 GPIO_ACTIVE_HIGH>;

          mode-gpios=<&gpio1 12 GPIO_ACTIVE_HIGH>;

          ant-sel-gpios=<&gpio1 10 GPIO_ACTIVE_HIGH>;

          pdn-gpios=<&gpio1 8 GPIO_ACTIVE_HIGH>;

          supply-voltage-mv=<3000>;

          trx-hold-time-us = <10>;

          pdn-settle-time-us = <17>;

          rx-en-settle-time-us = <10>;

          tx-en-settle-time-us = <10>;

    };

};

&radio {

    status = "okay";

    /* This is a number of antennas that are available on antenna matrix

     * designed by Nordic. For more information see README.rst.

     */

    dfe-antenna-num = <12>;

    /* This is a setting that enables antenna 12 (in antenna matrix designed

     * by Nordic) for PDU. For more information see README.rst.

     */

    dfe-pdu-antenna = <0x0>;

    /* These are GPIO pin numbers that are provided to

     * Radio peripheral. The pins will be acquired by Radio to

     * drive antenna switching.

     * Pin numbers are selected to drive switches on antenna matrix

     * desinged by Nordic. For more information see README.rst.

     */

    dfegpio0-gpios = <&gpio0 4 0>;

    dfegpio1-gpios = <&gpio0 5 0>;

    dfegpio2-gpios = <&gpio0 6 0>;

    dfegpio3-gpios = <&gpio0 7 0>;

    fem=<&nrf_radio_fem>;

};

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

Thanks!

[PaKa]

Output power from the SoC will be reduced when you add a FEM into the system. This as the output power will be SoC power + FEM gain. Add the FEM and test again.

[joey]

Thank you for your reply.

1、I have added the ant_sel pin in the Device Tree. How can I control this pin? Are the other pins automatically handled at runtime?

joey said:

nrf_radio_fem: nrf21540_fem{

          compatible="nordic,nrf21540-fem";

          tx-en-gpios=<&gpio1 9 GPIO_ACTIVE_HIGH>;

          rx-en-gpios=<&gpio1 11 GPIO_ACTIVE_HIGH>;

          mode-gpios=<&gpio1 12 GPIO_ACTIVE_HIGH>;

          ant-sel-gpios=<&gpio1 10 GPIO_ACTIVE_HIGH>;

          pdn-gpios=<&gpio1 8 GPIO_ACTIVE_HIGH>;

          supply-voltage-mv=<3000>;

          trx-hold-time-us = <10>;

          pdn-settle-time-us = <17>;

          rx-en-settle-time-us = <10>;

          tx-en-settle-time-us = <10>;

    };

2、Why does adding the FEM reduce the transmit power, and what is the purpose of this?I set the TX power of the nRF54 to 0 dBm in the DTM app, but the output power via the nRF21540 is only -8 dBm. VDD 3.0V