Tx Power using SoftDevices S140 nrf52840

[TigerD]

Hi,

I am using SD calls to start an advertisement of BLE_GAP_ADV_TYPE_NONCONNECTABLE_NONSCANNABLE_UNDIRECTED :

          sd_ble_gap_adv_start(m_adv_handle, APP_BLE_CONN_CFG_TAG);

The call to set TX power:

err_code = sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_ADV ,  m_adv_handle, POS_08dBm);

m_adv_handle is BLE_GAP_ADV_SET_HANDLE_NOT_SET,

It seems that tx power is set not.

Questions:

1.  how to create a valid handle of m_adv_handle for the call through S140 SD?

2. If NULL handle, can be used, how to set tx power correctly?

Thank You,

David Zhou

[haakonsh]

That looks like the correct API usage to me. 

"It seems that tx power is set not."
How do you know? Can you share any measurements with us?

[TigerD]

Hi Haakonsh,

My program is based on

     ..\nRF5_SDK_15.3.0_59ac345\examples\ble_peripheral\ble_app_beacon

and using softDevice call to Advertise:

    err_code = sd_ble_gap_adv_start(m_adv_handle, APP_BLE_CONN_CFG_TAG);

The call to set  TX POWER  with BLE_GAP_TX_POWER_ROLE_SCAN_INIT

   err_code = sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_SCAN_INIT, BLE_CONN_HANDLE_INVALID, -20 ); 

  doesn't change the TX power for Advertising ( it is easily testable, e.g. using Android phone, it always reports the same RSSI from the unit, no matter what setting of the tx_power ( int the above case, it is -20).

 ( I also tested with Proximity example, which is BLE API based, change tx power with BLE_GAP_TX_POWER_ROLE_ADV, will change the rssi from -50dBm to -100dBm, with 8 and -40 tx power settings respectively.)

But if the call set  TX POWER  with BLE_GAP_TX_POWER_ROLE_ADV  

  err_code = sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_ADV, BLE_CONN_HANDLE_INVALID, -20 ); 

The program generates run-time error with error code :  12292

Thank You

David

[haakonsh]

Have you tried calling sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_ADV, BLE_CONN_HANDLE_INVALID, -20 )  before you start advertiments? 

[TigerD]

I did. The call sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_ADV, BLE_CONN_HANDLE_INVALID, -20 ), is before start advertisements.

It generates 12292 run-time error.

David

[haakonsh]

Sorry I meant to use BLE_GAP_ADV_SET_HANDLE_NOT_SET as the connection handle.

[TigerD]

It is the same error 12292 from

err_code = sd_ble_gap_tx_power_set(BLE_GAP_TX_POWER_ROLE_ADV, BLE_GAP_ADV_SET_HANDLE_NOT_SET, 8 )

BLE_CONN_HANDLE_INVALID is defined as 0xFF

BLE_GAP_ADV_SET_HANDLE_NOT_SET is defined as 0xFFFF

I guess there is no essential difference.

Thanks,

David

[haakonsh]

An error 12292dec corresponds with 0x3004. From the sd_ble_gap_tx_power_set API this is an BLE_ERROR_INVALID_ADV_HANDLE. 

The API docs for the 'handle' parameter' says:
If role is 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 ble_gap_adv_properties_t::include_tx_power set.

I guess you've defined an advertising set when you set the advertisement data, you need to use this handle with sd_ble_gap_tx_power_set.

[TigerD]

I changed my program to use ble_advertising_start() to advertise. That solves my problem, because it has valid handle to set tx power.

Thank You,

David