Thank you.
I quickly read the gpsd howto and it explains what I want to do using
kpps on a raspberry. From there I can see a typical accuracy of 1uS, but
the informations of the live graphs page are precise down to the ns: are
these averaged?
What do you intend for granularity? Consider that I'm a newbie in
frequency/time specific terms.
Regards,
Ilia.
On 10/20/16 07:02, Gary E. Miller wrote:
Yo Ilia!
On Thu, 20 Oct 2016 06:15:39 +0000
Ilia Platone <[email protected]> wrote:
I am trying to take some timestamps of events on a GPIO using an ARM
SBC, and noticed that the kernel linux can be interfaced to a PPS
signal, wanted to sync another GPIO to a GPS receiver for time
reference.
You should check out the gpsd time howto, and ntpsec.
http://www.catb.org/gpsd/gpsd-time-service-howto.html
https://www.ntpsec.org
I need to know how much precise this system can be. How
much resolution can I obtain with a cheap receiver (maximum
quantization frequency)?
On average, on a RasPi 3, you can expect about
Formulas are well accepted.
How about a graph, or two? See attached. From the histogram, I suspect the
granularity is about 200 nano sec. From the offset graph you can
see how the offset jumps.
Here is the offset data on PPS v. the system clock:
Percentiles......
Min 1% 5% 50% 95% 99% Max
-21.645 -2.587 -0.834 -0.020 0.991 0.991 13.557 µs
Ranges......
90% 95% StdDev Mean Units
1.825 5.318 0.850 -0.006 µs
Or see a lot more live graphs here: https://pi4.rellim.com/day/
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
[email protected] Tel:+1 541 382 8588
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