connection and scan interval in multilink application

[Andreas48752]

Hi,

I am wondering how connection and scan interval work together when using multilink central device. I am starting scanning (scan interval and window 0x80) again after connection (connection interval 20 ms) is established. I would allow 10 simultaneously connections.

How does that work? If nrf5 is listening on the advertising channels, no communication with the connected peripherals is possible, right?

Thanks a lot.

[run_ar]

Yes, only one role/activity at the time. So you need to choose scan and connection intervals wisely. See the Primary channel scanner timing chapter of the Softdevice specification so see details on scanning. I would recommend you look through the whole Scheduling chapter when doing multi-role.

[Andreas48752]

Thank you for the answer and the links. That is what I was looking for.

I am not sure if I got that right:

So my goal are max. 20 simultaneous connections (con. interval 200 ms and gap event length set to 7.5 ms) and scanning window 50 ms  (scanning interval also 200 ms). This would be 20x7.5=150 ms for the connections and 50 left for scanning window. 

If I am using that there should not be any overlapping, right?

[run_ar]

From the sds: If short connection intervals are not essential to the application and there is a need to have a Scanner running at the same time as connections, then it is possible to avoid dropping packets on any connection as a Central by having a connection interval larger than ∑t_event-Cx + scanWindow + t_ScanReserved. The Initiator is scheduled asynchronously to any other role (and any other timing-activity), hence the initiator timing-event might collide with other timing-events even if the above recommendation is followed. 

I could not quickly find t_ScanReserved, but according to Bluetooth Low Energy scanner and initiator processor usage not a lot time should be needed. Consider maybe reducing the scan window by a couple of milliseconds to take that into account?