ble_gap_evt_adv_report_t beacons

[Abhishek]

Hi,

In one of my application based on SDK 15.2, I am using nRF52832 as a central scanning  device for 128 BLE beacons

My question is how often is the ble_gap_evt_adv_report_t data instance updated if I set the timeout value as BLE_GAP_SCAN_TIMEOUT_UNLIMITED. 

My understanding here is setting the timeout to BLE_GAP_SCAN_TIMEOUT_UNLIMITED  allows me for a continuous scan forever , but I need to know how is the gap advertisement report updated.

Thanks

Abhi

[Hung Bui]

Hi Abhishek, 

Please have a look at this message sequence chart: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v7.3.0/group___b_l_e___g_a_p___s_c_a_n___m_s_c___l_e_g_a_c_y.html?cp=4_7_3_1_2_1_5_14_0

As you can see, you will receive BLE_GAP_EVT_ADV_REPORT on every advertising packet received by the softdevice. In this event you will have an updated data instance of ble_gap_evt_adv_report_t .  After each BLE_GAP_EVT_ADV_REPORT  you need to continue scanning sd_ble_gat_scan_start() to be able to receive more advertising packet. 

[Abhishek]

Hi Hung,

Thanks for the response. 

I think I was not able to explain my question fully

1) I understand that sd_ble_gap_scan_start() needs to be started everytime we want to update to the report BLE_GAP_EVT_ADV_REPORT,

2) in the sd_ble_gap_scan_start()  there is a parameter scan_params--> timeout, this timeout if set to  BLE_GAP_SCAN_TIMEOUT_UNLIMITED  means scanning all the time and we do not need to call the sd_ble_gap_scan_start() again to start scanning again( correct me if I am wrong)

In this case how is the BLE_GAP_EVT_ADV_REPORT updated?

For example I have a beacon in surroundings which is advertising every 1 second , does the report BLE_GAP_EVT_ADV_REPORT also get updated every second ? 

Thanks

Abhi

[Hung Bui]

Hi, 

Abhishek said:

this timeout if set to  BLE_GAP_SCAN_TIMEOUT_UNLIMITED  means scanning all the time and we do not need to call the sd_ble_gap_scan_start() again to start scanning again( correct me if I am wrong)

No this is not correct. You will have to restart scanning regardless what timeout you set. 

If you have a beacon advertising every 1 second, you will receive BLE_GAP_EVT_ADV_REPORT every one second or earlier, if there are other advertisers around. 

[Abhishek]

Hi,

Can you be more specific on what does the BLE_GAP_SCAN_TIMEOUT_UNLIMITED imply ?

Thanks

Abhi

[Hung Bui]

Hi, 

If you set the timeout to a specific number , let says 10 seconds. If there isn't any advertising packet received in such 10 seconds you will receive an event BLE_GAP_EVT_TIMEOUT and scan will stop. 

If you set the timeout to BLE_GAP_SCAN_TIMEOUT_UNLIMITED , you will not receive BLE_GAP_EVT_TIMEOUT and scanning will not stop if there isn't any advertising packet received.