[ntp:questions] GPS_NEMA, but high offset and jitter?

Richard B. Gilbert rgilbert88 at comcast.net
Fri Feb 26 00:27:49 UTC 2010


Kelsey Cummings wrote:
> Rob wrote:
>> This is normal with NMEA.  You never will get stable time when using
>> an NMEA time source.  For that, you need PPS.  Your PPS is apparently
>> not working.
> 
> It feels like I must be missing something here, running with -d I can 
> confirm that PPS doesn't appear to be working - after enabling flag3 as 
> well.
> 
> 25 Feb 13:53:21 ntpd[75656]: 0.0.0.0 041d 0d kern PPS enabled
> 25 Feb 13:53:21 ntpd[75656]: 0.0.0.0 042d 0d kern PPS no signal
> ..
> 
> Is there any other way to watch the signal to see if it's reaching the 
> serial port correctly?
> 
> -K

There is a device called a "breakout box" that can be connected to a 
serial device and a serial port.  It will make all twenty-five pins
available for testing.  If you have only nine pins you'll need an 
adapter.  The more expensive devices will use bipolar LEDs to display 
the status of each pin.  Some will allow you to drive pins high or low.

You can probably pick one up on e-Bay for a not TOO outrageous price.
Don't pay big bucks for one, 99% of the time you'll use it as a paper 
weight or some such humble task.




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