nRF52840 BLE Multi-role Timing

[johnnyR]

Hi,

I want to configure the nRF52840 with Multi-role capability. I will be using the Central role as well as the peripheral role simultaneously. However, i'd like to maximize the ScanWindow to be equal with the ScanDuration. Which leaves technically no room for simultaneous Advertising from the peripheral role. How would the softDevice handle such cases. Let's say i'd like to set the advertising interval of the peripheral role to 20ms. Would this still be executed? If so how is the timing affected for both scanning and advertising? We know that transceivers can only be either Tx or Rx but not both at the same time. With the case stated above, how does it advertise when programmed to be scanning all the time as well?

Kind regards,

Erick

[run_ar]

Hi,

Scheduling priorities will be found here. SoftDevice timing-activities and priorities

Basically it will be first come, first serve until one of the roles has been blocked a few times, then that role will have priority over the other for the next event.

[johnnyR]

Hi,

Thanks for the answer. I highlighted a text that says "for a few times". Would we be able to define this "few number of times" that an advertising has to be blocked in order to get prioritized? 

[run_ar]

Hi,

This number is an internal parameter and subject to change. I checked with the team, and in your described usecase when one of the roles is blocked it will be scheduled for the next event. However if the advertisement is blocking the scan event, scanning will be cancelled for the entire interval. To avoid long periods without scanning the recommendation is to use shorter scan intervals. This means the scanner will spend some time changing channel, but you will avoid not scanning for long periods if an advertisement is scheduled instead of the scanner.