[ntp:questions] setting the time using gps-time and pps without ntpd?

Nicola Berndt nb at komeda-berlin.de
Tue Apr 22 09:59:50 UTC 2008


recently I tried building a microsecond precision timeserver using a 
gps-device with pps signal.

The gps-data is transmitted via usb, the pps signal via the rs232 
carrier detect line.

I tried several drivers and they all worked, but I had to figure that 
obviously my mainboard (via epia en12000EG) has terrible jitter. - unusable!

To solve the problem I think about simply setting the time every n 
seconds according to the collected gps time and the pps-signal. My 
system will run off for far less than a microsecond in an interval of 
let's say, 20 seconds or so. Like this I would implement a constantly 
jumping time, but the amount of jumps would be extremely small.

Since I learned that timekeeping is a very complex topic, I thought, I'd 
better ask on this list, before I build something troublesome without 
even knowing..

What do you think?

With best regards,
../nico berndt

More information about the questions mailing list