Peripheral, central and mesh simultaneously in nRF52840

[someone]

I know that RF52840 could act simultaneously as the Advertiser\Peripheral and Observer\Central and I saw Nordic's recent demo video of BT + Thread co-existence. However, it's unclear to me will it work if everything is "on" or there are some limitations on possible usage.

We try to build an application, which requires any of the following configurations:

1. Peripheral, central + Bluetooth mesh
2. Peripheral, central + Thread

I was told by a guy from Bluetooth SIG that the first option is not limited by the specifications and it all depends on a stack implementation, but generally must be possible.

Are any of these combinations possible? If no, I'd be highly appreciated if someone could explain the details of the limitation.

[Sigurd]

Hi,

Both of the configurations you list are possible.

Limitations:

1. Concurrent BLE + Mesh activity:

By design, the SoftDevice activity is prioritized over mesh activity. Therefore, you should keep the connection and advertisement intervals used by the SoftDevice as large as possible (i.e. infrequent) when using Bluetooth low energy connections. If scanning, keep the scan duty cycle as low as possible. You should also reduce mesh activity while the SoftDevice is doing fast advertising and continue normal activity after a connection is established.

2. BLE + Thread:

As shown in the concurrent Thread and Bluetooth 5 video, the radio time is divided between Thread and BLE. Using a arbitration algorithm and with the very short switching period on the nRF52 radio, you have a seamless transition between Thread and BLE. But note that due to nature of the time-multiplex solution, using the BLE Central role here is ineffective compared to a stand-alone BLE central.

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Only BLE: The nRF52 have support for 20 concurrent BLE connections , where you can freely configure each link in any combination between Peripheral and Central.

[Sigurd]

Hi ToasTer86,

Overall you will have less radio time available for BLE, so you will get a lower throughput compared to a stand-alone BLE central. Let's say that you are running BLE 4.2 with DLE and long ATT MTU, where you one a one-to-one link could get 775 Kbps. Let's say Thread uses 50% of the radio time, and that this leaves you with ~400 kbps for your BLE links. Dividing this across your 4 peripherals, you would maybe get around 100 Kbps max for each link. So for almost all regular BLE applications it will work perfectly fine. If you however experience any trouble with the BLE links, you could try to increase the BLE connection interval.