[ntp:questions] "Oneshot" time sync without risk of jumping time?

Jason Rabel jason at extremeoverclocking.com
Sun Apr 27 13:42:41 UTC 2014

> I want to keep the time updated on a small Embedded Linux device.
> The clock doesn't have to be very accurate. An offset of a few seconds 
> is OK.
> This small device only has Internet for a few minutes a day and I have 
> to pay for each byte that gets transmitted, so I want to keep the 
> traffic low.


If you want to keep track of time better without resorting to the Internet as much you could go a couple different routes.

1. Add a GPS module, preferably with a PPS output to your device. That will give you accurate time 24/7. However, you would need a
GPS antenna and visible sky access. GPS modules are so small and low-power, it's usually not too difficult to cram them into
embedded cases and leech power from the main board.

2. Replace the cheap crystal oscillator on the embedded device with a better TCXO or OCXO.

If you wanted to make a little bit of a jump in size and power you could use a Rubidium module, either to replace the device's
oscillator, or use as a PPS source.

Just some thoughts...

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