[ntp:questions] NTP rejecting SHM for NMEA GPS and PPS

David Taylor david-taylor at blueyonder.co.uk.invalid
Sat Aug 11 15:08:38 UTC 2018

On 10/08/2018 23:16, natal at datacloud.com wrote:
> I forgot to mention that I am using Ubuntu 16.04 and the GPS receiver is connected via USB

USB is not the best to get good results.  You need to connect the PPS 
signal directly to a port on the device - typically the CD (carrier 
detect) line on a _true_ serial port is used.  Likely the 
serial-over-USB is rejected because of excessive jitter.

I don't know whether you may have your "prefer" in the wrong place 
without looking in detail.  You need the "prefer" against a server which 
will provide the coarse seconds (i.e. a clock) otherwise the PPS edge 
will not be recognised (as NTP needs both coarse time and the exact 
second).  You may, or may not, be correct.

Web: http://www.satsignal.eu

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