Regarding setting Tx power to +8dbm

[Ravi Theja]

Hi,

 I am using Nordic nRF52840 SoC with nRF5_SDK_15.2.0_9412b96(SDK) and S140 softdevice. I tried to set Tx power to +8dbm using 

rc = sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_ADV ,m_adv_handle,+8); after calling advertising_init(); in ble_app_multipepripheral example.But when i see the RSSI signal in mobile using nRF connect for mobile app its showing maximum of -15dbm instead of +8dbm when i place the mobile near the device. The ret_code(rc) of this api sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_ADV ,m_adv_handle,+8); is 0 when i printed which means NRF_SUCCESS.Can anyone please help me why its showing -15dbm instead of +8dbm?

[awneil]

rc = sd_ble_gap_tx_power_set( BLE_GAP_TX_POWER_ROLE_ADV , m_adv_handle, +8 );

Are you sure that "+8" is the correct way to specify  the power?

What does the documentation say ... ?

How to properly post source code:

[Ravi Theja]

Hi awneil, Thanks for the quick reply.

I am placing +8 based on the API description.

/**@brief Set the radio's transmit power.
 *
 * @param[in] role The role to set the transmit power for, see @ref BLE_GAP_TX_POWER_ROLES for
 *                 possible roles.
 * @param[in] handle   The handle parameter is interpreted depending on role:
 *                     - If role is @ref BLE_GAP_TX_POWER_ROLE_CONN, this value is the specific connection handle.
 *                     - If role is @ref BLE_GAP_TX_POWER_ROLE_ADV, the advertising set identified with the advertising handle,
 *                       will use the specified transmit power, and include it in the advertising packet headers if
 *                       @ref ble_gap_adv_properties_t::include_tx_power set.
 *                     - For all other roles handle is ignored.
 * @param[in] tx_power Radio transmit power in dBm (see note for accepted values).
 *
  * @note Supported tx_power values: -40dBm, -20dBm, -16dBm, -12dBm, -8dBm, -4dBm, 0dBm, +2dBm, +3dBm, +4dBm, +5dBm, +6dBm, +7dBm and +8dBm.
  * @note The initiator will have the same transmit power as the scanner.
 * @note When a connection is created it will inherit the transmit power from the initiator or
 *       advertiser leading to the connection.
 *
 * @retval ::NRF_SUCCESS Successfully changed the transmit power.
 * @retval ::NRF_ERROR_INVALID_PARAM Invalid parameter(s) supplied.
 * @retval ::BLE_ERROR_INVALID_ADV_HANDLE Advertising handle not found.
 * @retval ::BLE_ERROR_INVALID_CONN_HANDLE Invalid connection handle supplied.
 */
SVCALL(SD_BLE_GAP_TX_POWER_SET, uint32_t, sd_ble_gap_tx_power_set(uint8_t role, uint16_t handle, int8_t tx_power));