BLE Adv Interval

[mich_x]

I am working on S140 on nRF25840. I am using the ble_app_beacon sample. I want to set the advertising interval smaller than 100ms while using non-connectable mode. But the BLE_GAP_ADV_NONCON_INTERVAL_MIN stops me. I wonder if there is any reason to set the minimum to 100ms, can I change it to smaller?

My second question is what is mode BLE_GAP_ADV_TYPE_ADV_SCAN_IND. It says Scannable undirected. Does it mean mode BLE_GAP_ADV_TYPE_ADV_NONCONN_IND cannot be scanned?

[RK]

The reason is the BLE spec says that non-connectable advertising shall not have an advertising interval less than 100ms and the softdevice is certified to follow the spec.

Correct, ADV_NONCONN_IND cannot be scanned. Again those terms are buried in the incredibly long BLE spec.

ADV_DIRECT_IND    - connectable, not scannable, directed
ADV_IND           - connectable, scannable, undirected
ADV_NONCONN_IND   - not connectable, not scannable, undirected
ADV_SCAN_IND      - not connectable, scannable, undirected

[endnode]

Btw. BT 5.0 lifted this limitation for non-connectable adv. interval and Nordic team plans to update S140/132 stacks in the future...

[RK]

I didn't know that - I guess I have to read the whole bloody spec again.

[mich_x]

What if I use connectable mode, while the scan machine does not try to connect. Does it make the communication somehow wrong? Can I set the adv interval smaller than 100ms.

BTW, the spec is long. My deadline doesn't allow me to read them through. :(

[Petter Myhre]

The 100 ms limitation is only for non-connectable advertising. You can use connectable advertising with less than 100 ms. Doesn't make your communication "wrong".

[endnode]

But then SD will accept CONNECT_REQ? And what if the FW doesn't want to handle any? Yes, it can terminate it straight away and also open another broadcasting in parallel so it will have "minimal" visible impact but there still we be some and also power consumption can be higher (if anyone cares). So having high frequency non-connectable broadcasts isn't such a bad idea...