[Thumbgps-devel] YEA! My Sure Electronics GPS just arrived.

[Ron Frazier (NTP)]

Since I wrote that, it seems to have centered itself around zero.  I now 
have a very nice + 1.2 ms / - 1.2 ms offset pattern.  Since I've been 
struggling to get anything under 50 ms with other technology, this looks 
really sweet to me.

http://dl.dropbox.com/u/9879631/Sure%20board%20first%20night%20pt1.jpg
http://dl.dropbox.com/u/9879631/Sure%20board%20first%20night%20pt2.jpg

Conversion of these images to jpeg reduced the clarity a bit, but you 
can still see what's happening.

Sincerely,

Ron


On 3/24/2012 4:21 AM, Andrew McGregor wrote:
> I know why it isn't centered... it's because it is taking a USB polling round trip to get the signal back.  The PPS happens somewhere between two polls every 1 ms, and it takes another 1 ms to come back.
>
> On 24/03/2012, at 2:38 PM, Ron Frazier (NTP) wrote:
>
>    
>> 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 zero, 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 I'm 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.
>>
>> Sincerely,
>>
>> Ron
>>
>>      



-- 

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Ron Frazier
timekeepingdude AT c3energy.com