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Re: [gpsd-users] Power saving


From: Ed W
Subject: Re: [gpsd-users] Power saving
Date: Tue, 27 Mar 2012 18:25:41 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:11.0) Gecko/20120313 Thunderbird/11.0

Hi

I found the power consumption of GPS antenna is too high for my specification. It is OK however to turn it on occasionally to re-caliber the system time, e.g. once per hour, in order to system system power. I am wondering if gpsd and automatically handle that while still working with NTPd. For example, if I only turn on gps power for every power, will GPSd still be able to correct the NTPd time during that small time window?

Dunno, but some things which might help:

Try chrony - it has additional features that assist with "disconnected" operation, in particular you can mark network based sources "offline" and "online" - quite possibly you can do the same with gps based sources. The "online" can causes chrony to become aware of a source becoming available and with suitable tweaking of burst/iburst you could take best advantage of a small time sync window...

Chrony is *probably* also going to do better with occasionally available sources due to the way it averages previous observations.

I don't see any fundamental reason though why you can't *do* what you ask. Just whether it meets your accuracy requirements.

Simple suggestion:

- Recent gpsd comes with a command line gpsdctl utility, so scripting is trivial
- Using cron, periodically wake up gps,
- add it to gpsd
- wake up chrony and tell it we are online
- pause as long as you can justify....
- reverse the above, take down chrony, remove the device from gpsd, turn off the device

None of the above is particularly dangerous or tricky or misusing a feature...

Good luck - would be interested to hear your results

Ed W



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