[ntp:questions] Linux 2.6 + PPS + ntpd?

Armen Babikyan armenb at ll.mit.edu
Fri Dec 30 00:10:29 UTC 2005


I have a Garmin GPS 25LP that I have connected to a serial port on my 
linux 2.6 laptop, and I need to get my system's clock synchronized with 
the PPS signal from the GPS.

I've verified that my GPS is indeed outputting the PPS signal 
(100ms-long pulse, once a second) with an oscilloscope and gpsd (which 
will output messages relating to getting or losing carrier detect on the 
serial line).

My problems comes in the kernel/ntp area.  After trying with RedHat 
Enterprise Linux's kernel (2.6.9-22.0.1.EL), vanilla 2.6.13 and vanilla, I've had unsuccessful results, ranging from kernel panics to 
test programs and ntp not producing correct output.

I've tried using both PPSkit and LinuxPPS - do you (collectively) had 
more luck with one over the other?  Has anyone had a post-2.6.9/pps/ntp 
configuration working somewhat recently?  I'd be interested to hear 
about specific software/hardware configurations to mimic a known-good 


  - Armen

Armen Babikyan
MIT Lincoln Laboratory
armenb at ll.mit.edu . 781-981-1796 

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