Channel sounding using multiple reflectors

[psychogenic]

I am attempting to do channel sounding with one initiator and two reflectors.  Switching between reflectors, by connecting to each in turn, does work, but it is very slow.

I have tried both

• connecting to both, enabling channel sounding at the time of connection and leaving it enabled
• connecting to both, enabling and disabling channel sounding with one reflector connection at a time

Both methods lead to successful sounding at the time of connection, but from the point where there have been CS events between the initiator and the second reflector it only ever works with the last connection made, and infinite aborted sub-events with the first device connection, basically getting a subevent_done_status of  BT_CONN_LE_CS_SUBEVENT_ABORTED with the reason being declared BT_CONN_LE_CS_PROCEDURE_ABORT_CHMAP_INSTANT_PASSED.

What is this error, why is it happening?  More importantly, what would be the steps to enable rapid switching or simultaneous CS with two reflectors?

I had some hope that the question posed on  channel sounding cs channel map update instant passing would give some info, but 3 months later Swathy's update is still pending. 

[Simonr]

Hi

The struct you provided should indeed do what you expect. However, the multilink feature for CS is not well implemented even in NCS v3.1.0, but we've made some changes to that on the main branch of NCS as of late, so we recommend that you try the same thing on ncs-main and see if it works there. If not, try following the recommendations here: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrfxlib/softdevice_controller/doc/scheduling.html#channel_sounding_timing 

Our hypothesis is that you are currently running into scheduling conflicts where conn events of connection B is overlapping with the channel sounding events of connection A when trying to reenable channel sounding on connection A, and this leads to the instant passed errors you're seeing.

Best regards,

Simon