Hello,
The last 25 hours I measured the jitter of my RPi-with-userspace PPS
processing. In the following graph you'll see those measurements. Each
row is an hour:
http://vps001.vanheusden.com/~folkert/jitter-hm.png
There's some kind of wave in it which I cannot explain: everything not
related to
I've now add Folkert's user-mode method to my NTP/Raspberry Pi notes here:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html#user-mode
Comments and corrections welcomed.
Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email:
After 51 minutes of ntpd run-time this gives:
remote refid st t when poll reach delay offset jitter
==
*firewall.intran 192.168.64.2 3 u7 64 3770.560 -0.506 0.493
From: folkert
[]
I'm surprised that the jitter goes down to 0.005 as I'm now measuring
the PPS from userspace. My program runs with real time scheduling and
maximum priority but still the kernel needs to do a context switch etc.
when it receives the pps pulse.
Folkert van Heusden
Hi David,
That sounds good, Folkert - perhaps you might publish the details
somewhere? I'd like to try it myself, but my Linux and C knowledge
is limited.
Here it is:
http://vanheusden.com/time/rpi_gpio_ntp/
Please let me know if anything is unclear: I'll then enhance e.g. the
readme.txt and
Hi David,
That sounds good, Folkert - perhaps you might publish the details
somewhere? I'd like to try it myself, but my Linux and C knowledge
is limited.
Here it is:
http://vanheusden.com/time/rpi_gpio_ntp/
Please let me know if anything is unclear: I'll then enhance e.g. the
readme.txt and
Thanks, Folkert, that's most helpful! One thing which is unclear to
me is what do you mean by pin 8? Is that a programming number, or
does it refer to the GPIO header? I did try and find this in the
RPi documentation, but it's not clear.
Check this picture:
Check this picture:
http://jeffskinnerbox.files.wordpress.com/2012/11/raspberry-pi-rev-1-gpio-pin-out1.jpg
GPIO pin 8 is in the upper right block with SPI in it.
GPIO 8 (CE0) is written above it. By the numbering on that diagram it is
physical pin 24.
[]
If I remember correctly, the kernel patch
David,
Fine, Folkert. The GPIO pins are numbered in your program exactly
as I would expect, and the diagram just confirms that. Yes, the
patched kernel can remain, and PPS operation should be unaffected.
I was able to drive the two pins (GPIO 18 and GPIO 8) in parallel,
and I have a
David,
[]
Ah!
Is the serial over usb working stable on your rpi?
I have lots of problems with usb devices dropping from the usb bus. Also
with a powered hub.
[]
The software compiled and installed without any issues. I've yet to
figure out how to get it to auto-start - you might like to add
Quoting folkert folk...@vanheusden.com:
:
+127.127.28.1.PPS.0 l48 3770.000
2.231 0.005
:
I'm surprised that the jitter goes down to 0.005 as I'm now measuring
the PPS from userspace. My program runs with real time scheduling and
maximum priority but still the
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Though I have been tied up with the wwvb stuff this is also on my list of
to do's.
I have had the RPI up and running and am looking forward to making a small
low power time server.
Thanks
Paul
WB8TSL
On Mon, Jun 17, 2013 at 5:31 PM, li...@lazygranch.com wrote:
Hi,
Ok today my friend Henk (Henk are you still subscribed here?) soldered
the raspberry pi on my adafruit ultimate gps breakout v3. Apart from the
soldering things were totally easy to get to work: only a few tweaks to
cmdline.txt and inittab and the serial data streamed in.
I decided _not_ to
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