BLE connection handle value scope

RE: BLE connection handle value scope

rolandash — Thu, 14 Dec 2017 16:09:10 GMT

Thanks Martin.

RE: BLE connection handle value scope

MartinBL — Thu, 14 Dec 2017 16:02:44 GMT

Yes, they will be unique.

RE: BLE connection handle value scope

rolandash — Wed, 13 Dec 2017 16:08:34 GMT

thanks for the advice Martin.

another related question to confirm is in case of mixed existence of peripheral links and central links, will each connection handle value still unique ?

RE: BLE connection handle value scope

MartinBL — Wed, 13 Dec 2017 13:11:05 GMT

I don't think there are any ways around sacrificing some CPU cycles on this one.

I suppose one obvious way to distinguish device A and device B when they connect is to check their respective addresses. Maybe you can add a reference to each device in an array and then associate connection handles with their respective device. Then, on each BLE event referencing a connection handle, you can iterate through the array of devices and check their connection handle?

RE: BLE connection handle value scope

rolandash — Mon, 11 Dec 2017 16:46:56 GMT

Martin, Probably i did not describe the question clearly. The root issue behind it is when there are multiple peer devices connecting at the same time to the same service/characteristic, I need to distinguish the data from different devices, so i can handle them differently, say, forward to different buffer for further processing.

Using conn handle indexing seems OK except it has to go through a lookup table given it is not continuous which may consume some CPU cycles, when there is more connection number.

So in this case i am not sure if bonding will help as in service write event seems no bonding information available help faster device indexing.

Is there any better way to do this?

thanks.

RE: BLE connection handle value scope

MartinBL — Mon, 11 Dec 2017 13:14:27 GMT

I'm not sure if I understand. Why would you have to pre-bond? Can't you bond the devices the first time they connect?

RE: BLE connection handle value scope

rolandash — Tue, 05 Dec 2017 07:59:25 GMT

thanks for the detailed answer. As in my use cases, the devices at the other end is random and un-predicate-able, so i can not pre-bond any devices. Is there any other better way to do this?

RE: BLE connection handle value scope

MartinBL — Mon, 04 Dec 2017 12:12:04 GMT

Hi,

I have heard this idea before, but there are some pitfalls:

Q1: Not necessarily. It is continuous as long as no devices disconnects. I.e. the first device will get handle 0, device number 2 gets handle 1, and so on. But if the first device disconnects, then device number 3 might get handle 0 again. Furthermore, due to the supervision timeout mechanism, it might in some cases take some time before the Softdevice detects that a device has lost its connection. And if the same device then tries to reconnect quickly (before the supervision timeout occurs) it might get assigned a new connection handle. Hence, it is actually possible that the same device has two connection handles at the same time, although only until the supervision timeout occurs.

Q2: Yes, the Softdevice will reuse connection handles, and a particular device will not necessarily get the same connection handle value on every connection.

Another solution to individually identify connected devices is to bond all your devices. Or you can use other information like e.g MAC addresses.