onboard clock

propan

Hi,

When does the onboard clock synchronisation happen?

I have a macro which starts logging the sensors at bootup. From the timestamps of downloaded data I can see that the clock resets to the time and date of last firmware update (at least in my case) after each reset. How can I force synchronisation of hw clock through API?

Thank you in advance

MetamotionR

FW: 1.3.6

Android API 3.3.0

Eric

Please provide some data that illustrates this timestamp issue you are seeing.

There is no real time clock on the device.  It does know how much time has elapsed and relies on the the host device to recalculate timestamps.  When connection is established, the API will query the current elapsed time reference point from the device.

propan

Ok, it makes sense then. The boot macro is programmed on one device and data is downloaded on another. I've shared serialization data, but sounds like the reference timestamp is hidden there, that is why the log timestamps are jumping back to serialization time after reset. Esentially, this means that there is no way to figure out timestamp of log entries after sensor has been reset while being offline.

Eric

You can approximate the actual time of the entries after reset by treating them as offsets from the last known timestamp prior to reset.

Out of curiosity, why are you resetting the board during a log session?

propan

Thanks, Eric, Happy New year, thank you for reliable support!

It is not that I'm planning to reset the device during logging, I'm trying to plan for the case, when sensor simply runs out of batteries and user continues measurements after charging it again.

I was planning to have a boot up macro which will start measurements om start while being offline. Looks like I would need to reastablish connection to the host after restart, figure out the time difference between the current device timestamp and the actual timestamp and by this link it to the actual world time.

Or I go into the sleeping mode or suspend the measurements when the battery charge is low in order to avoid running out of power.

Eric

Timestamps should be OK with 1 reset.  It's multiple resets without re-establishing connection that will result in time sync issues with the SDK.