How to set the nRF21540-DK using basic sample (peripheral nus) with 20dBm TX power ?

[Daewoong Kim]

Hello,

How to config FEM on "nRF21540-DK" to set the TX power as +20dBm ??

• I used the "perpheral_nus" sample (basic Bluetooth LE sample) in NCS 3.2.4 version
• Also, I understood that activating RF FEM in nRF21540-DK just can be applied based on prj.conf setup.
  • Is this wrong??

The following is my prj.conf setup, but except first row,
the others is not activated as shown in the figure below (yellow lines).

The comments indicate that "MPSL_FEM_ANY_SUPPORT" dependency is missing.

CONFIG_MPSL=y

CONFIG_MPSL_FEM=y

CONFIG_MPSL_FEM_NRF21540_GPIO=y

CONFIG_MPSL_FEM_NRF21540_GPIO_SPI=y

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=20

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTA=20

CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB_POUTB=10

CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y

Of course, I've build the project with target board nrf21540-dk, the related setup in devicetree already included..

-

I just want to activate FEM on the nRF21540-DK with building basic Bluetooth LE sample 

Please give me any comments 

Best regards,

Daewoong Kim

[Vidar Berg]

Hello,

When you use the nrf21540 DK as your build target, it should be sufficient to add the following to your project configuration to achieve 20 dBM output power:

# Desired output power on antenna 
CONFIG_BT_CTLR_TX_PWR_ANTENNA=20
# Select POUTA (default: 20 dBm) for nRF21540 FEM TX gain
CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB=20

Setting CONFIG_BT_CTLR_TX_PWR_ANTENNA to 20 is necessary here. Otherwise, it defaults to 0 dBm, and the controller will try to achieve this value at the antenna by reducing the output power of the nRF52840's RADIO so that RADIO.TXPOWER + CONFIG_MPSL_FEM_NRF21540_TX_GAIN_DB equals 0 dBm.

Best regards,

Vidar

[Daewoong Kim]

Thank you, Vidar

it works well

Best regards,

Daewoong Kim