Can a device simultaneously be a central and a peripheral?

[MichaelNordicUser]

Our products should connect to a central device. This central device should also be a peripheral which a phone can connect to. Will this be possible? If not, could the phone be a peripheral which is connected to by the central?

Additionally, can a device scan and broadcast simultaneously? Why and why not?

[Ulrich Myhre]

Hi,

The SoftDevices based on the s130 (s130, s132, s332 etc.) should all support concurrent Central, Peripheral, Broadcaster and Observer. The limitations are RAM and radio time. You can also only have one broadcaster and one observer at any point, and the roles will automatically switch to peripheral and central roles, respectively, if a connection occurs. So you will need to re-start advertising and/or scanning whenever a connection is created using any of those operations.

So you can have an observer and broadcaster, but since they share the same radio, they cannot actually run at the same (physical) timeslot. The SoftDevice scheduler handles this automatically for you, but it is possible to misconfigure the parameters so that the division of time is unfair. One example is setting scan window equal to the scan interval, where the radio will be busy 100% of the time. An advertiser/connection will then only get a small slice of time when the scheduler thinks it is important, and this could potentially lead to link loss or poor advertising conditions.

To re-iterate, the answer is yes, but you need to remember that all the roles share the same radio, and it has some physical limitations. Carefully selecting parameters for scanning, advertising, connection interval/supervision timeout is important for making a fair arrangement between the concurrent roles.