Central connect to Peripheral without scanning

RE: Central connect to Peripheral without scanning

Nick_RA — Thu, 11 May 2023 14:48:22 GMT

OK so it looks like in this instance I have a 1+ sec delay just to connect which I was hoping to short-circuit (a bit like ARP caching in networking parlence) but it doesn't look like I can do that. Ah well, at least I can set expectations before development so thanks.

RE: Central connect to Peripheral without scanning

Kazi Afroza Sultana — Thu, 11 May 2023 10:55:37 GMT

Yes.

When we do normal scanning then connecting, we are first reading the advertisements to find a device that we want to connect. In the advertisement event what we want to connect to, we call sd_ble_gap_connect, and one of the input parameters of this function is the address, which we get from the advertising packet. Then the central will continue to scan, because it needs to send the connection packet directly after an advertising packet.

If you skip the scanning and just connect, it will be able to connect to the first advertising packet that it picks up. But scanning and then connecting takes at least two advertising packets.

RE: Central connect to Peripheral without scanning

Nick_RA — Tue, 09 May 2023 15:46:23 GMT

nRF5 SDK, and yes the peripheral is advertising at 625ms interval.

So are you effectively saying there's no advantage, that connect is effectively the same as scanning with a whitelist?

Regards,

RE: Central connect to Peripheral without scanning

Kazi Afroza Sultana — Tue, 09 May 2023 13:14:46 GMT

Hello,

Are you using NCS or nRF5 SDK? In nR5 SDK, if central knows the MAC address of the peripheral, it is possible as long as the peripheral, you try to connect is advertising. The Softdevice will perform a scanning after the sd_ble_gap_connect() has been called regardless of the application has performed scanning or not.

Thanks.

Kazi