[time-nuts] Thunderbolt GPS rollover

Bob Camp lists at rtty.us
Fri Jun 8 00:02:58 UTC 2012


Hi

One could put in a routine that looks at the date the software was written and "fix" any date that shows up as being in the past. Simply *assume* it's a rollover error and move it up modulo the magic offset number. That way any particular rev of the software would be good for 20 years.

Bob

On Jun 7, 2012, at 7:44 PM, Mark Sims wrote:

> 
> When / how the Thunderbolt responds to a rollover event (either raw sat signal week number or internally biased week number based upon a fixed offset or date of manufacture) is not known.   The Trimble manual suggests that it adds a fixed bias to the transmitted week number and  evil things may happen on 30 Jul 2017.   That "feature" is not mentioned in the Thunderbolt-E manual.   Perhaps later revs of the Tbolt firmware have implemented a more robust week handling algorithm...  time will tell.   Or does anybody have a GPS signal simulator handy?  Enquiring minds want to know...
> 
> Lady Heather does have some code for tweaking the date as part of the calendar code (eg. letting one adjust the correlation constant for setting the origin of the Mayan calendar).   That could be used to tweak the date for a mis-behaving rollover.   Speaking of which,  there may never be a chance for rollover problems since the world ends this year...
> 
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