S140 6.0.0 SCANNING ISSUE

[Aylik]

Hi All!

Faced with big problem with SCANNING procedure (nRF52840)

We have a BLE network : one CENTRAL and up to 6 PERIPHERALs can be connected simultaneously to the CENTRAL.

Advertising period of Peritherals is 1 second.

THE PROBLEM:

if no connected devices, CENTRAL report "BLE_GAP_EVT_ADV_REPORT" occur each 1 sec very STABLE.

if connections established, CENTRAL report "BLE_GAP_EVT_ADV_REPORT" very not stable sometimes with 5..6 seconds delay , depends on conenction count.

SCANNING PARAM:

#define _SCANPARAM_ {                                         \
    .active   = 1,                                            \
    .interval = (uint16_t) MSEC_TO_UNITS(20, UNIT_0_625_MS),  \
    .window   = (uint16_t) MSEC_TO_UNITS(20, UNIT_0_625_MS),  \
    .timeout          = BLE_GAP_SCAN_TIMEOUT_UNLIMITED,       \
    .scan_phys        = BLE_GAP_PHY_1MBPS,                    \
    .filter_policy    = BLE_GAP_SCAN_FP_ACCEPT_ALL,           \
}

CONNECTIN PARAM:

#define _CONN_PARM_PREFF_ {
         .min_conn_interval = (uint16_t) MSEC_TO_UNITS(65, UNIT_1_25_MS), \
         .max_conn_interval = (uint16_t) MSEC_TO_UNITS(65, UNIT_1_25_MS), \
         .slave_latency     = 0,                                          \
         .conn_sup_timeout  = (uint16_t) MSEC_TO_UNITS(1000,UNIT_10_MS) } \

HOW to provide stable ADV report during CONNECTIONs or it is IMPOSSIBLE ?

waiting for answer.

[Edvin]

Hello,

Having a short scanning interval means that the softdevice has to change channel more often. Can you please try to increase the scanning interval a bit. Just for testing, try to set both the .interval and .window to something like 0x0FFF. 

BR,

Edvin

[Aylik]

Hi Edvin,

I tested > 100  variants, in my case, stable result only with use;

.interval = 3200 , .window  = 2615

all other cases work very unstable (10/10, 20/20, 0xfff/0xfff, 3200/3200, 3200/2000, etc ....) 

Please, exlain how it does work.

.. also, I find after ~ 2 minutes , Scanning again becomes unstable until RESET...

[Edvin]

Hello,

Sorry for the late reply. I just wanted to let you know that I have to check what the softdevice does with the scanning when it is in a connection, and gets a connection event within the scan interval. I am not sure whether it resumes the scanning afterwards, or if it waits for the next scan interval to resume the scanning.

I will come back to you as soon as I know anything.

 

BR,

Edvin