Scan vs adv intervals

[Johan.h]

I have a number of sensors, advertising data every 1 second, in a very low power consumption configuration.

The central device is scanning all the time, in order to receive advertising data from the sensors, so in order to have good chance to receive, I need a scan interval > 1 sec.

This setup already works, but now I need the central device will also advertise itself, so a mobile app will be able to connect and view data, change configuration etc.

So, I am not sure how to setup the adv parameters. It is ok if user on mobile will wait 1 or 2 seconds to get the advertised package and get connected, should I set the adv interval > 1 sec?

How does the BLE do this scan/adv time slots on the advertising channels, when I need it to scan 99% of the time, and advertise only 1%, for example?

Thanks

Johanan

[Vidar Berg]

Hello Johanan,

You can set the scan window equal to the scan interval if you want to maximize scanning frequency. The scheduler in the softdevice controller will ensure that scanning is performed whenever you are not advertising as illustrated here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/softdevice_controller/doc/scheduling.html#primary-channel-cooperative-scanning 

So, I am not sure how to setup the adv parameters. It is ok if user on mobile will wait 1 or 2 seconds to get the advertised package and get connected, should I set the adv interval > 1 sec?

Yes, it's OK to use longer adv. intervals. The drawback is that it will increase the discovery time and the time it will take to establish a connection for the Phone central.

Best regards,

Vidar

[Johan.h]

Thanks for your answer and link, which explains a lot.

Johanan