[ntp:questions] YEA! My Sure Electronics GPS just arrived.
Ron Frazier (NTP)
timekeepingntplist at c3energy.com
Tue Mar 27 00:28:21 UTC 2012
On 3/26/2012 2:15 PM, Gom wrote:
> Even with multimedia timer on its smallest resolution, you will run
> into the 1 ms barrier under windows.
> To do better you need to enable interpolation, this simple operation
> will improve your jitter by at least 10x.
I'm trying various options of NTPD_USE_INTERP_DANGEROUS, flag3 on the
"20" driver, and process priority to see what has any effect. Keep in
mind though, I'm still running everything through a serial - usb
converter so that probably puts a limit on things.
> Le 25/03/2012 23:06, Ron Frazier (NTP) a écrit :
>> On 3/24/2012 12:46 PM, unruh wrote:
>>> On 2012-03-24, Ron Frazier (NTP)<timekeepingntplist at c3energy.com>
>>>> I now have the PPS circuit working on the Sure board. I have not
>>>> soldered it yet. I just taped a jumper wire between the PPS test point
>>>> at the edge of the board and the DCD pin 1 on the RS-232 port. The
>>>> serial data is coming in through the Trendnet TU-S9 serial - USB
>>>> converter, which is passing DCD. I'm getting + .5 / - 1.5 ms offsets.
>>>> The PPS is nowhere to be seen on the statistics screen, but it is
>>>> obviously working. I don't know why it's not more centered around
>>> Peaked around zero in comparison with what? Remember that the serial to
>>> usb of dcd and then the decoding of that interrupt is going to
>>> institute delays. It should always be later than "true time".
>> I just meant that the offsets were shifted more toward the positive on
>> the graph rather than being centered around zero. They seem to be
>> centered around zero now.
>>>> and maybe that will change. However, my total peak to peak range of
>>>> offset variance is 2 ms, and that's coming through USB. If I can
>>>> maintain that level of accuracy, and it's consistent with UTC, then
>>>> very happy. That's plenty good for my purposes. I still may try to run
>>>> it through a real serial port on another machine just for kicks.
>>> You can get 1us, not 1ms that way. But if a factor of 1000 is
>>> for you, then what you have is fine.
>> I don't have to have 1 us. I just want the computer's clocks to be right
>> and to be doing better than I can with internet servers. In that regard,
>> any offsets better than 50 ms are good. I plan to test this GPS for a
>> while and and make sure it's stable. Then, I want to set up every
>> computer so it can use the GPS if it's attached. Then, I'll try the real
>> serial thing on the PC that has a port. Eventually, I want to make
>> probably that one a server for all the rest. I'll probably have to give
>> the server a fixed IP address in my router since those can change when
>> DHCP assigns them.
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