nrf52840 concurrent bluetooth 1M and coded communication

[MatejSt]

Hello!

We are trying to make a family of devices that would be based on nrf52840. The devices would communicate between each other via Bluetooth Long Range (CODED PHY). In addition to communicating with each other we need the devices to be accessible to a smart phone or tablet on the 1M PHY. For example we would like to connect to device A via smart phone and change some settings on device B in real time. In other words device A would receive the settings via 1M PHY and forward them to device B via CODED PHY in real time. So my guess is that in this case device would need to switch between the two physical layers quickly in order to communicate with both the smart phone and device B at the same time on the two different physical layers.

So my question is, is this possible/realistic to achieve? And if so, could you kindly point me to some working example of a similar nature?

Thank you in advance!

[haakonsh]

The SoftDevice uses whatever PHY is assigned to a connection, if connection A uses Coded PHY it will use Coded PHY for any Connection event related to Connection A, and if Connection B uses 1mbps PHY it will use 1mbps PHY for any connection event related to Connection B. The SoftDevice will switch to whatever PHY it needs to use depending on what connection it will serve. You can, therefore, use different PHYs for different connections on the same device.

Do note that the connection event length of a Coded PHY event is 8x longer that for a 1mbps event, given the same payload. This means that the connection interval of the 1mbps link should be fairly permissive, i.e. min >= 7.5ms, max >= 100ms. Other than that there should be no problems. 

There are 2 ways to use Coded PHY, either you advertise and scan on Coded PHY, or your advertise and scan in 1mbps and then switch to Coded PHY after you've established the connection. 

See:

1. BLE Multi-link Example and BLE Blinky Application.
   
   
2. sd_ble_gap_scan_start, ble_gap_scan_params_t, extended, and scan_phys.
   
   
3. sd_ble_gap_adv_start, sd_ble_gap_adv_set_configure, ble_gap_adv_params_t, primary_phy, and secondary_phy.
   
   
4. sd_ble_gap_phy_update.

[MatejSt]

Thank you for your reply!

So just to confirm... In the BLE Multi-link example if I was to configure some central-peripheral connections to CODED PHY and some to 1M PHY I would still be able to turn on all peripheral leds at the same time (roughly) from the central?

[haakonsh]

Yes, the radio is re-configured to use whatever PHY is valid at any given time by the SoftDevice. 

If you've got 3 DKs you can test it by doing a phy update on one of the active connections, from 1mbps to coded phy. Check out the "Relevant Message Sequence Charts" listed in sd_ble_gap_phy_update for more information.