Advertize and scan only on 2M PHY

[blac01]

Hi,

Is it possible to advertize and scan only on the 2M PHY and w/o using at all the 1M PHY on nRF52840/S140 system ?

The actual system is running fine if we use the 1M PHY and then switch to 2M but we'd like to always use the 2M as once our central is connected to 2 peripherals but during the connection phase of the 2nd periph the BW is limited as the central is back to its 1M.

Thank

[Stian Røed Hafskjold]

It's not possible to have the primary advertising channel to advertise on the 2M PHY, from the Bluetooth 5.1 core spec (vol 6, part B, section 2.3, table 2.3). ADV_EXT_IND is only supporting 1M and Coded PHY. The extended advertising packet can use the 2M PHY, but the scanner must first scan on 1M/coded to "find" the 2M extended packet.

[blac01]

Thx for the answer.
If the central has a connection with a peripheral at 2M and a scan is launched in parallel to discover a 2nd peripheral how is handled the PHY ?
In particular in our config we have set a connection interval to 7.5 ms and a connection event to 3.75 ms. So I'm wondering if the PHY is switched between 1 and 2 M in each connection event.

[Stian Røed Hafskjold]

The softdevice will switch between the PHY which is needed for the specific task that is scheduled. If a connection event is coming up, the the radio will be configured with 2M if the connection is set up to use 2M, and then if a scanning interval is coming up it will switch to 1M. With a connection interval of 7.5 ms and a event length of 3.75 ms you don't have much time left to scan, so I'm not sure if this will work in practice.

[blac01]

One last question.

What is the PHY switch time between 1 and 2 M ?

[Stian Røed Hafskjold]

Since scanning and connection are two separate BLE events, it shuts down the radio, configures it with the PHY and frequency needed, enables the radio and wait for it to be ready. The most significant time is from when you issue the enable task, to the radio is ready. You can find the numbers here: https://infocenter.nordicsemi.com/topic/ps_nrf52840/radio.html?cp=3_0_0_5_19_14_7#unique_447117906 More specifically t_{RXEN,FAST,BLE,1M}