[ntp:questions] lots of GPS modules and info at SparkFun

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Tue Feb 14 18:52:19 UTC 2012

Hi Paul,

I noticed the module you mentioned uses the Sirf III chipset.  I've been 
doing a good bit of experimentation with a GlobalSat BU-353 (no PPS) 
which is also based on the same chipset.  David Taylor was nice enough 
to post my experience on his website from a series of dialogs we had.  
You might find the information useful, including how I programmed the 
unit.  The GlobalSat specific data may not apply to the unit you 
mentioned, but the Sirf stuff should apply to either.  If you want to 
look it up, the link is below.  I don't think that page mentions it, but 
I now have my unit outputting only the GPZDA NMEA sentence, which seems 
to give the most accurate timing information and the least jitter.  I 
don't think this sentence has any position information.  Obviously, with 
PPS, the accuracy of the NMEA is less important.  But, with my current 
setup, I'm getting pretty consistent +/- 6 ms accuracy.




On 2/12/2012 9:31 PM, Paul J R wrote:
> Figure I might chime in with the gps unit I got and if your in Aust i
> think its probably about the best deals i've seen that has a pps line
> (theres also another one they have if you can do smd soldering thats
> cheaper again).
> http://www.twig.com.au/store/product_info.php?products_id=108&osCsid=148a3e8759d5ae6b8ab6f3f0489e0fd4
> <http://www.twig.com.au/store/product_info.php?products_id=108&osCsid=148a3e8759d5ae6b8ab6f3f0489e0fd4>
> I was looking to put together the dirt-cheapest ntpd machine with pps i
> could, and that was the cheapest i could find (though i havent had the
> time to put mine together as yet because the pps line does need some
> soldering). I also happened to have a wyse terminal (x86 based)
> http://www.wyse.com/products/hardware/thinclients/S10/index.asp that i
> picked up for around 30$ (currently running ubuntu 10.10 server without
> too much drama).
> On 13/02/12 13:00, Dave Hart wrote:
>> On Sat, Feb 11, 2012 at 10:20, Terje Mathisen wrote:
>>> unruh wrote:
>>>> GEt the manual from Mediatex MTK NMEA Packet User Manual, which gives a
>>>> far far more extensive set of nmea programming instructions for the
>>>> chipset that Sure uses.
>>> Does that one have more info than my current program?
>>> C:\c2\nmea-mtk>Release\nmea-mtk.exe -?
>>> nmea-mtk (c) 2011 Terje Mathisen
>>> Syntax: nmea-mtk [options]
>> The SURE electronics unit people have been buying as an affordable
>> refclock for those with soldering skills and time is the reference
>> design for the SkyNet SKG16AH chip known as SKG16B [1].  Unruh and
>> Terje are talking about a MTK (I or II?) chipset.  Does anyone know
>> the relationship between the two?  I'm wondering if there's a way to
>> refer to both unambiguously, or if they're subtly different beasts.
>> After a little more digging I came across a nice comparison table of
>> chipsets [2] which suggests to me the SKG16AH is derived from or
>> clones the interface of a MTk design.  If you have additional insight
>> or can correct me, I'd appreciate it.
>> [1] http://www.skylab.com.cn/datasheet/SkyNav_SKG16AH_DS.pdf
>> [2] http://wiki.openstreetmap.org/wiki/GPS_Chipset
>> Cheers,
>> Dave Hart


(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
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Ron Frazier
timekeepingdude AT c3energy.com

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