How to synchronize time across multiple nrf5340?

[Divya BM]

Hi,

We are trying to synchronize time across 3 nrf5340, where one will be master and the other 2 nrf5340 will have to synchronize their time with the master.

1. All 3 devices will have BLE functionality. Just with BLE stack on all 3 devices, Can we expect synchronization between master and the 2 slaves. If so, what is the deviation possible in the 3 devices?

2. For other Nordic platforms, we see there is softdevice support to synchronize clocks with multiple devices. Is there any equivalent samples available for nrf5340 with zephyr?

Regards,

Divya 

[Sigurd]

Hi,

Divya BM said:

If so, what is the deviation possible in the 3 devices?

This will depend on how you have implemented the time synchronize method, and the accuracy of the crystal you are using. The Bluetooth spec sets the minimum possible connection interval to be 7.5ms, so you would need account for this latency as well. 

Divya BM said:

For other Nordic platforms, we see there is softdevice support to synchronize clocks with multiple devices.

What are you referring to here ? Is it this blog post ? https://devzone.nordicsemi.com/nordic/short-range-guides/b/bluetooth-low-energy/posts/wireless-timer-synchronization-among-nrf5-devices

In that case, we have a similar timeslot mechanism in NCS, see this link:http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.3.0/nrf/samples/mpsl/timeslot/README.html

[Divya BM]

Hi Sigurd,

The blog post you are referring to is correct. However, the timeslot sample does not appear to be the same. Can you please elaborate on how this could be used for time synchronization.

Regards,

Divya

[Simonr]

Hi Divya

Sigurd is out of office, so I'm taking over the case in his stead. The samples are not the same, but the basic concept in the guide is, where each node (all three nRF5340s) keeps a free-running timer with a counter. This free-running timer is still the basis for the synchronization, where one node will be the master, with a goal to have the other nodes synchronize their timers with the master. There will be some adjustments to the sample necessary of course, but by following the same principles as in the blog post Sigurd linked to, you should be able to achieve the same for your 5340s.

Best regards,

Simon

[Divya BM]

Hi Simon,

Thanks for your input.

Regards,

Divya