Frame of reference
You’d think it would be easy to have perfectly synchronised time. After all, time’s all around us. 28 sattelites do nothing but shout it out into the ether. The GPS sattelites, I mean. Expensive atomic clocks floating above our heads meant to do nothing else but tell time so we could tell the place.
It is kinda easy. All you need is a GPS receiver and ntpd, right? The NTP daemon knows about the GPS receivers and can get time information from them.
Wrong. You also need a serial port, and these days, it’s a rare commodity, at least on my server motherboard which only has one. And it’s taken up already by the UPS too.
And you also need to actually connect the GPS to the serial port and make sure it’s supplied with power cause batteries will only last it nine hours at most.
So in the end it comes out to:
- A serial GPS cable with a car lighter socket plug for power. ($35)
- A USB to serial converter ($20)
- A car lighter socket, from an extension cord or something else. ($10) (it might not be optimal, but I’m too stingy to cut up a $35 cable, so it’ll be necessary.)
- A 12 volt power supply ($10) (actually, Garmin eTrex wants 3 volts and not 12, but see above)
$75 just for cables. And that not counting that I have the GPS receiver already. It’s either that or making my own Garmin connector, which is not that easy since they use a highly unorthodox plug, unlike anything I’ve ever seen on any other device. You literally have to cut one out of a brick of plastic and set up holes for contact springs.