Can one deivice be both the central device and peripheral device?

[Ziyao Zhou]

Hi,

I am wondering whether I can have one "RELAY" device in BLE communication (not BLE mesh), I have look through this forum but only saw some example 5 years ago. As I am using the NCS 2.91, Is there any sample for this task? Could you please give me some information?

Thank you so much!

[Einar Thorsrud]

Hi

Yes, there is no problem for a device to act as both central and peripheral (and based on that act as for instance a relay). You can see an example of this in the Bluetooth: Central and Peripheral HRS sample.

[Ziyao Zhou]

Hi, some other question would be whether the "relay" will decrese the throughput and increase latency? 

[Einar Thorsrud]

Hi,

Yes. There is only a single radio, and the radio time (and any CPU processing as well) are shared between all the connections. So more connections (in any role), will reduce the potential throughput for each one. For latency it is a bit more complicated, as that depend on the connection parameters, but if you need to increase the connection interval, that will lead to an increase in latency. You can read more about int under Scheduling in the SoftDevice Controller documentation.

[Ziyao Zhou]

Thank you so much for your reply!

[Ziyao Zhou]

Hi

I have encountered some problems: I have a peripheral node (A), a central/peripheral node (B), and another central node (C). Basically, I want to use B to relay A's data to C, similar to a router. However, there is some control siganl from C to B, I can only receive A's data on B, however, I cannot receive from C.

I am here to confirm whether my design is applicable, if yes, do you have some samples or advice?

Thank you!

[Einar Thorsrud]

Hi,

What you descrie is possible, but you need to handle relaying of the data i the application layer (for instance receive a notification on one end, and send on another (or write, or similar dependign on how you have designed this).You can see an example of a relay device (your B) in Bluetooth: Central and Peripheral HRS.