https://devzone.nordicsemi.com/f/nordic-q-a/64429/synchronize-central-connection-attempts-with-known-but-slow-peripheral-advertising-intervalHello, I have a system composed of one central that needs to 1) briefly connect to many (100+) peripherals, 2) download a small amount of data from each, and then 3) disconnect. At the moment, the peripheral devices advertise with a 1 second intervalen-USTelligent Community 13Sun, 02 Aug 2020 07:52:37 GMThttps://devzone.nordicsemi.com/thread/262671?ContentTypeID=1Sun, 02 Aug 2020 07:52:37 GMT137ad170-7792-4731-bb38-c0d22fbe4515:46a4608d-d194-4cc6-a93d-16532f512231Dmitry<p>Hi Kyle,</p> [quote userid="3119" url="~/f/nordic-q-a/64429/synchronize-central-connection-attempts-with-known-but-slow-peripheral-advertising-interval"]My reading of the S140 documentation regarding &quot;initiator timing&quot; leads me to believe that if I call sd_ble_gap_connect() immediately after seeing an advertisement that SoftDevice will do nothing until the connection is established or the connection timeout occurs.&nbsp; Is this a correct interpretation?[/quote] <p>Yes, it will scan for advertising packets from connection target(s), also serve all established connections at the same time.</p> [quote userid="3119" url="~/f/nordic-q-a/64429/synchronize-central-connection-attempts-with-known-but-slow-peripheral-advertising-interval"]Instead of wasting this time between advertisements, I&#39;d like the central to keep scanning for additional peripherals (and service any existing connections). Do you have recommendations for how to make this system as efficient as possible?[/quote] <p>As I understood your case, you need to query each of 100+ devices once a 15 minutes. You can set a whitelist of up to 8 devices, it will connect to the first found one. From peripheral side, you can put device to 15-minute sleep right after successful connection, then wake up and advertise all the time until it&#39;s found by central again, maybe increasing advertising interval after 1 minute. </p> [quote userid="3119" url="~/f/nordic-q-a/64429/synchronize-central-connection-attempts-with-known-but-slow-peripheral-advertising-interval"]Alternatively, it is possible for the peripherals to be modified to send 2-3 closely-spaced advertising events every 1 second so that sd_ble_gap_connect() could be called with a short scan timeout?[/quote] <p>I didn&#39;t get how this could help... Anyway, peripheral sends 3 advertising packets one-by-one on three channels (37,38,39), but you cannot know an exact time point - a random value is added to advertising interval each time.</p><div style="clear:both;"></div>