Why nRF52 can not set Tx Power to -30 dBm?

[Genyu]

Hello,

nRF51 can set Tx Power to -30dBm.

Why nRF52 can not set Tx Power to -30 dBm?

Do you have any reasons?

[Roger Clark]

Looks like the hardware does not support that power setting

You can set it to -30dBm but you'll get -40dBm

See nrf52_bitfields.h

   #define RADIO_TXPOWER_TXPOWER_Pos (0UL) /*!< Position of TXPOWER field. */
    #define RADIO_TXPOWER_TXPOWER_Msk (0xFFUL << RADIO_TXPOWER_TXPOWER_Pos) /*!< Bit mask of TXPOWER field. */
    #define RADIO_TXPOWER_TXPOWER_0dBm (0x00UL) /*!< 0 dBm */
    #define RADIO_TXPOWER_TXPOWER_Pos3dBm (0x03UL) /*!< +3 dBm */
    #define RADIO_TXPOWER_TXPOWER_Pos4dBm (0x04UL) /*!< +4 dBm */
    #define RADIO_TXPOWER_TXPOWER_Neg30dBm (0xD8UL) /*!< Deprecated enumerator -  -40 dBm */
    #define RADIO_TXPOWER_TXPOWER_Neg40dBm (0xD8UL) /*!< -40 dBm */
    #define RADIO_TXPOWER_TXPOWER_Neg20dBm (0xECUL) /*!< -20 dBm */
    #define RADIO_TXPOWER_TXPOWER_Neg16dBm (0xF0UL) /*!< -16 dBm */
    #define RADIO_TXPOWER_TXPOWER_Neg12dBm (0xF4UL) /*!< -12 dBm */
    #define RADIO_TXPOWER_TXPOWER_Neg8dBm (0xF8UL) /*!< -8 dBm */
    #define RADIO_TXPOWER_TXPOWER_Neg4dBm (0xFCUL) /*!< -4 dBm */

[endnode]

Roger is right, nRF52832 supports only this list of Tx Power settings in 2.4GHz RADIO peripheral HW block, see also here.