adding nrf21 FEM to new 53 board

[Mustafa]

Hello,

I would like to confirm this procedure and hopefully correct me if I miss any steps.

So to add FEM nrf21 (only active by gpio mode) to new nrf53 board:

first step:

add fem node to nrf5340_cpunet.dts

    nrf_radio_fem: fem {

        compatible = "nordic,nrf21540-fem";

        rx-en-gpios = <&gpio0 29 GPIO_ACTIVE_HIGH>;

        mode-gpios  = <&gpio1 10 GPIO_ACTIVE_HIGH>;

        pdn-gpios   = <&gpio1 4 GPIO_ACTIVE_HIGH>;

        tx-en-gpios = <&gpio0 19 GPIO_ACTIVE_HIGH>;

        supply-voltage-mv = <3000>;

    };

&radio {

    fem = <&nrf_radio_fem>;

};

second step:

add    hci_rpmsg.conf in child_image

# Enable FEM with the highest TX power

CONFIG_BT_CTLR=y                                                                  

CONFIG_BT_CTLR_TX_PWR_ANTENNA=127                                  

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=20

CONFIG_MPSL_FEM=y

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=20

CONFIG_MPSL_FEM_NRF21540_GPIO=y

---------------------------------------------------------------------

Did I miss something else?

Thanks in advance!

ncs: SDK v2.4

soc: nrf5340 (custom board)

fem: nrf21540

[Håkon Alseth]

Hi,

 

Here is a thread covering the same question(s):

 Using nrf5340dk with the nrf21540 EK 

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=20

You should keep this value to the default, as described here:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/device_guides/working_with_fem.html#setting-the-fem-output-power

CONFIG_BT_CTLR_TX_PWR_ANTENNA=127   

This line shall be equal to your expected/wanted output power.

 

If you are targeting your product for europe, please note that +10 dBm is the max, as stated here in this comment:

 RE: Using nrf5340dk with the nrf21540 EK 

  

Kind regards,

Håkon

[Mustafa]

Thank you Håkon!

Just for clarification, to add nrf21 fem we need only to add the gpio declaratin and radion node only in nrf5340_cpunet.dts right?

after that I noticed some examples where CONFIG_MPSL_FEM_xxxxx settings are placed either in main proj.conf or in hci_rpmsg ? which one is the correct file for those settings?

Besides that I got a lot of warnings when I enabled gpio mode using CONFIG_MPSL_FEM_NRF21540_GPIO , is that the correct config to do that or I need to add more dependencies?

Best regards

[Håkon Alseth]

Hi,

 

It should go in the network core image, which is "hci_rpmsg" for NCS v2.4 or older, while it is named "hci_ipc" in ncs v2.5.x and newer.

If you look at this answer, it shows how to verify that your configurations have been applied properly:  RE: Using nrf5340dk with the nrf21540 EK 

 

Kind regards,

Håkon