DTS files for a custom board NRF5340 + NRF21540

RE: DTS files for a custom board NRF5340 + NRF21540

Kenneth — Sun, 03 Mar 2024 19:34:56 GMT

I recommend to attach a spectrum analyzer for proper measurements. In general you may not see a difference on the output power with and without nRF21540. Instead you have the possibility to set higher output power than what the nRF5340 alone can support, the library will use the PA gain + nRF output power to get the closest setting that combined give the output power you want.

But to answer your question, you likely should set CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=20. Also you may find this useful:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/device_guides/working_with_fem.html#ug-radio-fem

Kenneth

RE: DTS files for a custom board NRF5340 + NRF21540

msfassarella — Thu, 29 Feb 2024 20:22:23 GMT

Hi Kenneth.

First of all, thanks for your reply.

In these days I was trying to confirm the hardware design and for this purpose the NRF21540 GPIOs were manually controlled. I confirmed that the hardware design is working and the RF power control by the Mode pin is ok too.

I tried configure CPU Net like described above and stopped the manual control over it (ant-sel-gpios and spi-if were removed)

Inside the \build\hci_rpmsg\zephyr\zephyr.dts I found the following references to FEM

	radio: radio@41008000 {
			compatible = "nordic,nrf-radio";
			reg = < 0x41008000 0x1000 >;
			interrupts = < 0x8 0x5 >;
			status = "okay";
			dfe-supported;
			ieee802154-supported;
			ble-2mbps-supported;
			ble-coded-phy-supported;
			fem = < &nrf_radio_fem >;
			ieee802154: ieee802154 {
				compatible = "nordic,nrf-ieee802154";
				status = "okay";
			};
		};

and

	nrf_radio_fem: nrf21540_fem {
		compatible = "nordic,nrf21540-fem";
		tx-en-gpios = < &gpio1 0xd 0x0 >;
		rx-en-gpios = < &gpio0 0x1e 0x0 >;
		pdn-gpios = < &gpio0 0x1a 0x0 >;
		mode-gpios = < &gpio1 0xe 0x0 >;
		supply-voltage-mv = < 0xce4 >;
		phandle = < 0x2 >;
	};

the \build\hci_rpmsg\zephyr\.config has the following

# CONFIG_SHELL_BT_NUS is not set
# CONFIG_SHELL_IPC is not set
# CONFIG_MPSL_FEM_ONLY is not set
CONFIG_MPSL_FEM_ANY_SUPPORT=y
CONFIG_MPSL_FEM_NRF21540_GPIO_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=y
CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=10
CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=20
CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB=10
CONFIG_MPSL_FEM_NRF21540_RX_GAIN_DB=13
# CONFIG_MPSL_FEM_NRF21540_RUNTIME_PA_GAIN_CONTROL is not set
# CONFIG_MPSL_FEM_POWER_MODEL is not set
CONFIG_MPSL_FEM_DEVICE_CONFIG_254=y
CONFIG_MPSL_THREAD_COOP_PRIO=6
CONFIG_MPSL_WORK_STACK_SIZE=1024
CONFIG_MPSL_TIMESLOT_SESSION_COUNT=0
# CONFIG_MPSL_ASSERT_HANDLER is not set

CONFIG_DT_HAS_NORDIC_NRF21540_FEM_ENABLED=y

the the \build\zephyr\zephyr.dts has the following

	gpio_fwd: nrf-gpio-forwarder {
		compatible = "nordic,nrf-gpio-forwarder";
		status = "okay";
		nrf21540-gpio-if {
			gpios = < &gpio1 0xd 0x0 >, < &gpio0 0x1e 0x0 >, < &gpio0 0x1a 0x0 >, < &gpio1 0xe 0x0 >;
		};
	};

I redo the test and both scan and advertisment are working.

However, the advertisement has a less rssi power than I expected.

When I did the same test, but controlling the gpios directly like described in NRF21540 datasheet, the RSSI was bigger.

How can I make sure that the NRF21540 is working with 20dB configuration instead of 10dB?

How CPU Net choose the value on NRF21540 pin Mode ?

RE: DTS files for a custom board NRF5340 + NRF21540

Kenneth — Mon, 26 Feb 2024 17:22:03 GMT

Hello,

The easiest may be to look at the added overlay files when including the nrf21540ek shield:
https://github.com/nrfconnect/sdk-nrf/tree/main/boards/shields/nrf21540ek

When building for instance the peripheral uart with the nrf21540ek you simply follow:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bluetooth/peripheral_uart/README.html#fem-support

If you want to observe what is actually added during build you can checkout dts and kconfig in:
appcore: \build\peripheral_uart\zephyr\zephyr.dts (\build\peripheral_uart\zephyr\.config)
netcore: \build\hci_ipc\zephyr\zephyr.dts (\build\hci_ipc\zephyr\.config)

Alternatively here is how to add the nrf21540ek shield for a generic nRF5340 example:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/device_guides/working_with_fem.html#programming

This example show how to set CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL to control output power dynamically:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/samples/bluetooth/hci_pwr_ctrl/README.html

Best regards,
Kenneth

RE: DTS files for a custom board NRF5340 + NRF21540

dstarling — Sat, 24 Feb 2024 23:56:13 GMT

I also have a similar issue with a custom board, any response? Thanks