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Onboard ECU real time clock error.


redmist
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I'm attempting to get the onboard logs to be displayed with Trackvision (a data video overlay). I can latch the data to the video sucessfully. However after after a minute or so of video the sync is obviously out by a half second or so. I would estimate that I'm loosing about 4-5 seconds of data sync every 10 minutes of gopro footage.

I wondered how the clock worked with the onboard logging. Simon thought that it was based on an iterative cycle and excessive load on the ECU could see the clock thrown out. However I've seen 'stalls' in data that would indicate that when the ECU is busy, data isn't logged the clock still functions.

If it is a constant clock error I can allow a slip in trackvivion. (I gather the processor is either slightly under or over clocked??) However if it is as Simon stated based on ECU load and in iterative process count, then there is no way I can predict where and when I need to allocate additional 'slip'.

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Hi again Daniel,

I have spoken to one of the engineers and this is what he has said:

He has an 0.8% error in time over the duration of the log.  There is no issue with the ECU running out of time or grunt to store the logs.  However, there is no real time clock keeping track of exact time so data is not time stamped.  Data is sampled every so many ms depending on the sample rate.  If there are small errors it can accumulate to a significant amount over a long log. 

I am assuming that to import the log files there has been some sort of conversion software written as we do not offer exporting. This conversion software could be used to scale the sample time stamps accordingly.  Also the video will need to be checked to ensure it is also accurate in its timing.

If you want more details or to correspond further on this please email tech@linkecu.com


Cheers,

Scott

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