[time-nuts] RasberryPi, timing and GPS receivers

xaos at darksmile.net xaos at darksmile.net
Wed Oct 17 19:51:03 UTC 2012


Tom,

Thank you and nice to be back!
Was working major hours for a while.
Workin' for a living :)

Now, I must confess that this project is sort of a
milestone for me.

Those who hate kids (I know you are out there !)
can stop reading now :)

My daughter, who just turned six, has been very curious
about what I do with all my machines.

I have taught her how to properly solder and she can spot
a cold joint and is very adamant about such things.

So, I have been thinking about making a small project
with lights etc. I don't have that much time
and I also want to experiment with the RPI so,
I can combine projects.

Given that an NTP server will not be as much fun
in terms of lights and so on, but I think
it will be more fun when the intricacies
of time are explained.

She is already very interested in puzzles and stuff
so I figure I'll encourage her.

I was actually very sneaky with getting her
interested in puzzles and stuff.

You see we both love "Gravity Falls" which is
this amazing Disney Channel series
that has crazy puzzles in it and it is a challenge
to figure out what is hiding in each episode.

Using that as the start, I explained
more things to her about puzzles and math
and she absolutely loves it.

So, to sum up (and sorry for the long post)
I think an NTP server with a tiny
footprint is just the ticket.

Your comments are most welcome.

Oh, and it would be nice to get
micro-second accuracy.

George, N2FGX

Quoting Tom Van Baak <tvb at LeapSecond.com>:

>> Question: What GPS timing module should I go with? No more Motorola
>> Oncore so what's best right now? Who sell modules? What are the price
>> ranges?
>>
>> Your comments are most welcome.
>>
>> -George, N2FGX
>
> Hi George,
>
> Welcome back to the list; you've been quiet for a long time. This  
> sounds like a great project. I hope you keep us informed with  
> progress and also make the results available.
>
> You should be able to find GPS modules with sub-microsecond 1PPS for  
> $25. Check sparkfun.com or the "Skylab" chip used on the  
> www.leapsecond.com/pages/MG1613S board. This and other chip  
> solutions require SMT/PCB mounting, connectors, external antenna and  
> cabling which can add to the net cost of complexity.
>
> A number of people I know who want an inexpensive, turn-key,  
> sub-microsecond, embedded GPS timing solution continue to chose the  
> Garmin 18x/LVC. These are nice because of the high-gain integrated  
> antenna (they work indoors), compact encapsulated design, and  
> extreme ease of use (5V, ground, 1PPS).
>
> /tvb
>
>
>> A new LEA6-T single piece cost IIRC 190EUR from the webshop.
>> A LEA5-T was IIRC half price.
>>
>> And a little caution: the LEA5 modules use considerably more power during
>> aquisition than the LEA4 did and the LEA6. IIRC we measured up to 150mA
>> (compared to <100mA with LEA4). I don't know the Rasberry, but i guess
>> that should be not a proble, but you should check for it nevertheless.
>>
>> Attila Kinali
>
> Attila,
>
> I'd say the u-blox 5T or 6T is rather over-kill for George's  
> application, both in price and performance (and learning curve and  
> integration). Remember that the world of NTP is milli- and  
> microseconds. State-of-the-art GPS timing receivers and GPSDO are in  
> the nano- and picosecond accuracy/jitter range.
>
> /tvb
>
>
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