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

[Dave Taht <dave.taht@gmail.com>]

My kvetch is that I never know what units anything is in anymore.

On Sat, Mar 24, 2012 at 7:14 AM, Ron Frazier (NTP)
<timekeepingntplist@c3energy.com> wrote:
> 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
>>>
>>>
>
>
>
>
> --
>
> (PS - If you email me and don't get a quick response, don't be concerned.
> I get about 300 emails per day from alternate energy mailing lists and
> such.  I don't always see new messages very quickly.  If you need a
> reply and have not heard from me in 1 - 2 weeks, send your message again.)
>
> Ron Frazier
> timekeepingdude AT c3energy.com
>
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-- 
Dave Täht
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