Compilation Error when Configuring NRF21540 on NRF5340

[kpi_xie]

I've been using ICMSG's IPC to exchange HCI messages between the netcore and appcore, and using SPI to exchange HCI information between the host and appcore. This setup enables HCI message transfer between the netcore and the host, and it works properly.

However, when I configure the NRF21540 FEM in the netcore, I get an error indicating that mpsl_work_q is undefined in hci_driver.c. I traced the code and found that mpsl_work_q is defined in mpsl_init.c, and it requires CONFIG_MPSL_FEM_ONLY=n. But when CONFIG_FEM=y is set, it automatically selects MPSL_FEM_ONLY.

So it seems like there's a conflict between my HCI and FEM configurations. How can I configure it to ensure both FEM and HCI are enabled at the same time?

[Hieu]

Hi kpi_xie,

What application are you having on the netcore? A regular BLE controller, or something custom of your own?

What version of the SDK are you using?

Hieu

[kpi_xie]

my sdk is ncs 2.6.1

The netcore has a simple program whose function is to send messages from the BLE rx_queue to the appcore via ICMSG IPC, and forward the messages received through IPC to the Bluetooth module via bt_send. The program is based on the hci_spi implementation but replaces SPI with IPC.

Below are the configuration items related to FEM and HCI in my prj.conf.

CONFIG_BT=y

CONFIG_BT_HCI_RAW=y

CONFIG_BT_MAX_CONN=8

CONFIG_BT_TINYCRYPT_ECC=n

CONFIG_BT_HCI_RAW_RESERVE=1

CONFIG_FEM=y

CONFIG_FEM_AL_LIB=y

CONFIG_MPSL_FEM=y

CONFIG_SPI=y

CONFIG_SPI_NRFX=y

CONFIG_NRFX_SPIM0=y

# CONFIG_MPSL_FEM_ONLY=y

CONFIG_MPSL_FEM_NRF21540_GPIO=y

# CONFIG_MPSL_FEM_NRF21540_GPIO_SPI=y

CONFIG_MPSL_FEM_NRF21540_RUNTIME_PA_GAIN_CONTROL=y

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=7

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB=7

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=7

CONFIG_MPSL_FEM_NRF21540_RX_GAIN_DB=13

The configuration related to FEM in the DTS overlay file of netcore.

&spi0 {

    status = "okay";

    cs-gpios = <&gpio0 11 GPIO_ACTIVE_LOW>;

    pinctrl-0 = <&spi0_default>;

    pinctrl-1 = <&spi0_sleep>;

    pinctrl-names = "default", "sleep";

    nrf_radio_fem_spi: nrf21540_fem_spi@0 {

        compatible = "nordic,nrf21540-fem-spi";

        reg = <0>;

        spi-max-frequency = <8000000>;

        status = "okay";

    };

};

&radio{

    /delete-property/ ieee802154-supported;

    fem = <&nrf_radio_fem>;

};

/ {

     nrf_radio_fem: nrf21540_fem {

        compatible = "nordic,nrf21540-fem";

        tx-en-gpios = <&gpio0 6 GPIO_ACTIVE_HIGH>;

        rx-en-gpios = <&gpio0 5 GPIO_ACTIVE_HIGH>;

        pdn-gpios = <&gpio0 4 GPIO_ACTIVE_HIGH>;

        ant-sel-gpios = <&gpio1 14 GPIO_ACTIVE_HIGH>;

        mode-gpios = <&gpio1 15 GPIO_ACTIVE_HIGH>;

        spi-if = <&nrf_radio_fem_spi>;

        supply-voltage-mv = <3000>;

        status = "okay";

    };

}

[Hieu]

Are you basically creating your own netcore application based on an HCI sample then?

You might need full fledge MPSL and not just the FEM part of MPSL. Try using:

CONFIG_MPSL=y
CONFIG_MPSL_FEM_ONLY=n

Also, for further debugging, you will want to look at the compiled .config file as well, to check which Kconfig has taken effect.

[kpi_xie]

Are you basically creating your own netcore application based on an HCI sample then?

yes, base on the sample hci_spi 

I tried adding CONFIG_MPSL_FEM_ONLY=n to my prj.conf file, but CONFIG_MPSL_FEM_ONLY=y still appears in the final .config file. It seems this is because in the fem_al Kconfig, CONFIG_MPSL_FEM_ONLY is automatically selected when CONFIG_FEM=y.

So the error still persists.

[Hieu]

OK, do you mean you are using CONFIG_FEM, which selects CONFIG_MPSL_FEM_ONLY?

Do you need CONFIG_FEM for any particular reason?

If not, please remove it. Use only CONFIG_MPSL and CONFIG_MPSL_FEM, and maybe explicitly disable CONFIG_MPSL_FEM_ONLY.

[kpi_xie]

I don't necessarily need to configure CONFIG_FEM=y, it's just to get the nRF21540 working. Since this is our first time using the nRF5340 and NCS SDK, sometimes the configuration might not be appropriate. I followed your suggestion and removed CONFIG_FEM, but the same error still occurred. After removing CONFIG_FEM_AL_LIB, it compiled successfully.

Now my configuration items in prj.conf are as follows:

# CONFIG_FEM=y

# CONFIG_FEM_AL_LIB=y

CONFIG_MPSL_FEM=y

CONFIG_SPI=y

CONFIG_SPI_NRFX=y

CONFIG_NRFX_SPIM0=y

# CONFIG_MPSL_FEM_NRF21540_GPIO=y

CONFIG_MPSL_FEM_NRF21540_GPIO_SPI=y

CONFIG_MPSL_FEM_NRF21540_RUNTIME_PA_GAIN_CONTROL=y

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=13

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB=7

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=13

CONFIG_MPSL_FEM_NRF21540_RX_GAIN_DB=13

The relevant configurations in the final generated .config file are as follows:

#

# Multiprotocol service layer (MPSL)

#

# CONFIG_MPSL_FEM_ONLY is not set

CONFIG_MPSL_FEM_ANY_SUPPORT=y

CONFIG_MPSL_FEM_NRF21540_GPIO_SUPPORT=y

CONFIG_MPSL_FEM_NRF21540_GPIO_SPI_SUPPORT=y

CONFIG_MPSL_FEM_NCS_SUPPORTED_FEM_USED=y

CONFIG_MPSL_FEM_API_AVAILABLE=y

CONFIG_MPSL_FEM=y

# CONFIG_MPSL_FEM_NRF21540_GPIO is not set

CONFIG_MPSL_FEM_NRF21540_GPIO_SPI=y

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=13

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=13

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB=7

CONFIG_MPSL_FEM_NRF21540_RX_GAIN_DB=13

CONFIG_MPSL_FEM_NRF21540_RUNTIME_PA_GAIN_CONTROL=y

CONFIG_MPSL_FEM_POWER_MODEL=y

CONFIG_MPSL_FEM_POWER_MODEL_NRF21540_USE_BUILTIN=y

CONFIG_MPSL_FEM_BUILTIN_POWER_MODEL_UPDATE_PERIOD=2000

CONFIG_MPSL_FEM_DEVICE_CONFIG_254=y

The gain values obtained using the functions mpsl_fem_pa_is_configured and mpsl_fem_lna_is_configured are consistent with what I set in prj.conf, but when I scan the broadcast packets of the nRF5340, the RSSI does not seem to have any significant change. Is there any other way to determine if my FEM is working properly?

[Hieu]

We are diverging to a different topic now, while on DevZone we would like to keep each case focused on one topic. This is a quick answer, but for further follow-up, please have a new case.

These configs likely have some issue

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=13
CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB=7
CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=13
CONFIG_MPSL_FEM_NRF21540_RX_GAIN_DB=13

Think of POUTA and POUTB as quick preset gain level that can be switched to using the GPIO interface. The nRF21540 by default has 10dB and 20dB gain for those output. It has one-time programmable registers to override that level.

The CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA and POUTB config is to tell the system what the hardware nRF21540 has been configured to. Unless you have configured those OTP registers, don't set them

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB is meant to be use when using the GPIO interface without the MODE pin. Refer here.
I don't remember clearly if it works in your context. If RSSI doesn't change at all, then it probably isn't.

Another thing is that this only sets the gain. However, MPSL controls both the output gain and the nRF5340's TX Power. It could be that MPSL is still targeting 0dBm total TX Power, thus it could be lowering the nRF5340's TX Power, resulting in a lower total result. Because of the wrong POUTA config, it is likely doing the math wrong.

You should use CONFIG_BT_CTLR_TX_PWR_ANTENNA instead. MPSL will use its own algorithm to finely change nRF5340 TX Power and the nRF21540 gain (over SPI) to get as close to the configured value as possible, taking into account also influences from temperature and voltage.

Hope that helps. For further issues with this topic, please open a new case.