Re: 📡 Synchronization of timestamps, using Bluetooth Connection Event?
Re: 📡 Synchronization of timestamps, using Bluetooth Connection Event?
- Subject: Re: 📡 Synchronization of timestamps, using Bluetooth Connection Event?
- From: Spero Koulouras <email@hidden>
- Date: Tue, 12 Feb 2019 19:27:55 -0800
Julian - Have you read this paper:
https://www.eit.lth.se/sprapport.php?uid=945
It is pretty on-point for what you are trying to achieve.
On Tue, Feb 12, 2019 at 3:26 AM Julian Vogels <email@hidden>
wrote:
> Dear list,
>
> Thank you for interesting topics and your support in the past.
>
> We’re building a peripheral device (Nordic nRF52840) which needs to be *time
> synchronized* with the central device (iOS device) once on connection.
> When sending a timestamp, we have unknown, noticeable latency. This is
> because we cannot know the time it takes until one packet is processed on
> the central side, sent, and then received and processed on the peripheral
> side. However, we do know that there are Connection Events (CEs) occurring
> every Connection Interval (30 ms), where the packets are exchanged. We were
> planning on using the CEs to infer the actual time of send/receive, as the
> event is happening at the same time on both sides and has a very short
> duration.
>
> On the peripheral device, we are able to generate an interrupt when the CE
> occurs. *On the iOS device, we are unable to detect when a Connection
> Event is occurring*.
> Is there any way to get the synchronized Bluetooth clock tick (Connection
> Event) on iOS? Or maybe we’re on the wrong track altogether?
>
> Any other ideas on how do you synchronize two timestamps on peripheral and
> central device? (We already have clock drift compensation by the way, I am
> just asking about timestamp sync.)
> Our requirement is a latency/jitter under 5-8 ms.
>
> I hope I sparked someones interest in this engineering problem! Please
> send me a message if anything is unclear.
>
> All the best,
>
> Julian
> <http://www.soundbrenner.com> *Julian Vogels*
> CTO & Co-Founder
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