Connection stability with S130

RE: Connection stability with S130

Marius Heil — Fri, 08 Jan 2016 09:34:29 GMT

Hello, thank you. I am currently going over all SoftDevice calls and I am checking my error handling. When I am done, I will have to see if the behaviour remains the same.

I am using S130 v1.0 production, I am using some GAT procedures to build connections, but afterwards, I am using only GATT writes to communicate and connection losses should not occur. I am indeed using scatternets, but I do not have loops. Drift should therefore be carried through the tree.

My current test was only using 8 devices, so I do not think that they chose the same hopping scheme, which is picked randomly as I think?

I will have a look for the NRF_ERROR_BUSY as you propose, but I'll have to understand some of these errors a little better before I handle them, so I will open another Question.

Thank you

RE: Connection stability with S130

vich — Wed, 06 Jan 2016 05:14:58 GMT

It is strange you receive BLE_GATTC_EVT_TIMEOUT, when using supervision timeouts of 6s, and if you do correctly implement GATTC responses on your peer. Please be aware that in S130 v1, APIs do return NRF_ERROR_BUSY, APIs need retry (future releases SD API will better mitigate this).

If you need greater support, one of our support engineers will be glad to assist you.

Cheers, Vinayak

RE: Connection stability with S130

vich — Wed, 06 Jan 2016 05:09:09 GMT

But, some known factors that could affect my earlier statement are, if you are forming scatternet using multiple S130 firmware leading to connection loops, then synchronization could end up in a deadlock if Centrals and Peripherals in your loop be Central and Peripheral respective at all times (i.e. at tN chip1 is central and chip2 too is central).

Another factor, if you do have two independent BLE connections of same connection intervals between chip1-chip2, chip3-chip4 and they coincidentally use the same hop sequence, then overtime they will drift into each other so to cause CRC error on air, leading to connection loss.

continued...

RE: Connection stability with S130

vich — Wed, 06 Jan 2016 05:08:37 GMT

Hi Marius,

We do stress test the multiple concurrent connections. Please provide details of your firmware (SD versions, GAP and GATT procedures exercised, etc.), to better understand your observations.

I would like to bring your attention towards the fact that peripheral links drift in time and overlap over multiple Central links in time on a chip, but as you have 100ms and 6s timeout, each link should sync within few retransmissions; hence disconnections should not be observed.

continued...