[ntp:questions] Trying to use Dimension 4 time keeper

David Taylor david-taylor at blueyonder.co.uk.invalid
Tue Sep 10 04:59:20 UTC 2013


On 09/09/2013 20:57, W. eWatson wrote:
[]
> It moves many seconds in a short time, say a day or two. How is GPS
> going to help? Does it provide access via a USB port.

You can use GPS over a serial-to-USB converter.  You may also find that 
your motherboard has a COM port header even though it's not brought out 
to the back - that's the way to get best reults.  The serial output 
alone doesn't provide very good results, although if you can turn up the 
baud rate high (e.g. 115,200 baud) it can reduce some of the jitter, as 
might getting the GPS to send just one sentence.  If (and it may be a 
big ask) the serial-to-USB sends the DCD line, you can use the PPS 
signal from the appropriate GPS to get significantly better performance 
than using Internet servers alone.

Some GPS/PPS devices I have used are listed here:

   http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html#GPS-devices

To get the best timekeeping, I would recommend that you up#grade to the 
current Meinberg port (4.2.6p5), and then copy the current development 
version binaries on top of a working 4.2.6p5 installation.  The binaries 
can be had here (except for Windows 2000):

   http://www.satsignal.eu/ntp/x86/index.html

Be sure to backup your 4.2.6p5 installed binaries, just in case.

For 0.1s accuracy, from Brian's observations, it seems that a local 
GPS/PPS receiver would be well worth the effort.  You could also add a 
low-cost Linux box into the mix with a built-in GPS/PPS receiver, and 
sync the Windows systems from that.  Here's the sort of size I am 
talking about:

   http://www.satsignal.eu/ntp/RaspberryPi-2-with-Adafruit-GPS.jpg

A credit-card sized box.
-- 
Cheers,
David
Web: http://www.satsignal.eu



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