What's the easiest way to make Busybox keep correct time?

[K.S.]

Cathey, Jim <jcathey <at> ciena.com> writes:

> 
> I don't know how all this is put together on your
> particular system, but I had experience once where
> an ill-advised attempt to keep the HW clock in sync
> resulted in destruction of the system's EEPROM in
> which the time offset and first-order drift correction
> factors were kept.  The adjustment was designed, by
> the system's authors, to be applied MANUALLY, after
> a sufficient amount of time had passed to develop a
> good baseline for drift.  By jinking it automatically,
> rather often, the 10,000-write-cycle EEPROM was destroyed
> in a matter of weeks, as I recall.

I'm not sure what they are using for memory in this device, but the
published specs say this:

RAM: 1GB DDR3
Flash: 512MB NAND Flash

I would assume that the flash memory holds the firmware and that everything
else is written to the DDR3.  At least I would hope that is the case.

Right now I am not using hwclock, just ntpd, and as noted it does seem to be
keeping the hardware clock more or less in sync.

> The moral is, don't go messing with stuff if you don't
> understand how it works.

Well, if I didn't want to be able to record shows on a schedule, that might
be good advice.  I was simply trying to find a workable solution to this
issue.  And anyone else that encounters this problem would likely do the same!

> I am still running one of these systems in my basement,
> it's been running for close to twenty years and without
> connection to the internet, and its clock is as spot-on
> as one could expect.  (Its cron is running sprinklers and
> outdoor lighting, so it's easy to verify the clock by
> observation.)  I've adjusted the clock only a handful of
> times, it learns and refines the drift every time I
> correct it.  Which is not often!

I would HOPE that flash memory has improved in the past 20 years, but since
you brought this up, would you care to share the procedure you have used to
get the time that accurate?  And do you have to run something at every
reboot to do the time correction, or is this a "set it once and forget it"
type of thing?

If I could get it to where the time drift was less than about one second per
week, that would probably be acceptable.