How long does it take for the new negotiated connection interval to get applied?

[Justin]

Hello,

I am using nrf52832 as a peripheral and running SD S112, nordic UART Profile and SDK 17.1.0 on it.

I am requesting the update connection parameter between  60ms to 105ms. I  see that the central has accepted the request and has also sent the LLCP connection update Indication.

However I see that for about 8-9 secs the peripheral is still using the old connection interval. ( my old connection interval is 1005ms)

What could be the reason for new connection interval not getting set immediately ?

In the attached sniffer log please refer to line 1272. 

Thank you. sniffer_log.pcapng

[Sigurd]

Hi,

This is determined by the master.

In the LL_CONNECTION_UPDATE_IND packet the new connection parameters is set to be applied at connection event 371. The LL_CONNECTION_UPDATE_IND packet was sent at connection event 362.

Current CI ~1second * (371-362)= 9 seconds before it takes affect.

[Justin]

Thank you Sigurd  for the answer. This is really super helpful.

Is there a way by which on peripheral side we can know that the  central has accepted the parameter update request?

For e.g. any callback event ? I know on_conn_params_evt() that is registered in cp_init.evt_handler.

Will this set event after the LLCP connection update Indication or right after when connection interval change is requested?

[Sigurd]

Hi,

The SoftDevice will generate the event BLE_GAP_EVT_CONN_PARAM_UPDATE, and the connection param module will give you the event BLE_CONN_PARAMS_EVT_SUCCEEDED when this happens.

Also see this MSC, https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v7.2.0/group___b_l_e___g_a_p___c_p_u___m_s_c.html