Precision Time Protocol – Windows 10 implementation
On Sat, Aug 10, 2019 at 9:02 AM Adam Kumiszcza akumiszcza@gmail.com wrote:
On Fri, Aug 9, 2019 at 1:01 PM shouldbe q931 shouldbeq931@gmail.com
wrote:
On Thu, Aug 8, 2019 at 4:07 PM Adam Kumiszcza akumiszcza@gmail.com
wrote:
Although there is one method using WSL, there is also the "native" method
"Precision Time Protocol - Try it out!"
Thanks! The link at the bottom is to a .doc file, which gives some
explanations. I'll try it out more thoroghly later. (
https://aka.ms/PTPValidation).
Some of the required links do not work, though, so it all seems a long way
till stable I guess.
I've not tried it yet, the links all worked for me. In case it is a setting
in your word viewer, I have saved it as a PDF (attached)
I have run PTP on a rPi 3B without any kernel modifications as a
grandmaster (with a ublox GPS to provide time and PPS), and experimented
with different NICs (intel, broadcom and solarflare, all with HW
timestamping) as clients in x64 hosts.
What type of PTP did you use? ptpd (https://github.com/ptpd/ptpd) or
linuxptp (http://linuxptp.sourceforge.net/)?
I used ptpd
I've tried the latter, and used the following ntp.conf (part of it here):
#PPS Kernel mode
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 time1 +0.000000 flag3 0 refid PPS
tos mindist 0.002
#GPS (NMEA)
server 127.127.20.0 mode 89 minpoll 4 maxpoll 4 iburst prefer
fudge 127.127.20.0 flag1 0 flag3 0 time2 0.059089 refid GPS stratum 2
#local PTP reference
server 127.127.28.0
fudge 127.127.28.0 refid PTP
/etc/linuxptp/ptp4l.conf has the following lines:
clock_servo ntpshm
ntpshm_segment 0
priority1 10
priority2 10
(the rest was left as default)
The ntp.conf should take the NMEA feed (as "wall clock" time) and PPS.for
precise time, and ideally a connection from other NTP servers to ensure
that the NMEA feed is "sane" If the host is also running as a PTP GM, it
should not be feeding PTP time (that it is generating) back into NTP.
I ran ntp (ntpsec) fed from gpsd for time and PPS, and then just ran ptpd
as a GM, taking its time from the "trained" (by ntp) clock on the rPi
/etc/linuxptp/timemaster.conf is as follows:
Configuration file for timemaster
[ntp_server localhost]
minpoll 4
maxpoll 4
[ptp_domain 0]
interfaces eth0
delay 10e-6
[timemaster]
ntp_program ntpd
[chrony.conf]
include /etc/chrony.conf
[ntp.conf]
includefile /etc/ntp.conf
[ptp4l.conf]
[chronyd]
path /usr/sbin/chronyd
[ntpd]
path /usr/sbin/ntpd
options -u ntp:ntp -g
[phc2sys]
path /usr/sbin/phc2sys
[ptp4l]
path /usr/sbin/ptp4l
But I think this shows it does not really interact with ntp:
pi@zegar:~ $ ntpq -c "cv &3"
associd=52436 status=00f1 15 events, clk_no_reply,
device="SHM/Shared memory interface", timecode=, poll=1850, noreply=1850,
badformat=0, baddata=0, stratum=0, refid=PTP, flags=0
(maybe because there's nothing connected on the other side, but I guess
noreply means no reply from PTP daemon?)
Best regards,
Adam
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It is my understanding that the latest version of the RPi (Pi4) has a
native full speed Ethernet interface, not through USB.
I also read that it needs a heat sink.
Didier KO4BB
On Fri, Aug 9, 2019 at 6:04 PM David J Taylor via time-nuts <
time-nuts@lists.febo.com> wrote:
You already have a PPS signal from your existing GPS, so I was thinking
simply of distributing that the the Windows PCs, and feeding it to the
serial port's DCD signal.
I will try that. I guess you can connect serial port directly to my
Uputronics expansion card (
https://store.uputronics.com/index.php?route=product/product&path=60_64&product_id=81)
while still attached to Raspberry Pi. Problem is, I'm a software, not a
hardware guy. No idea about soldering. Time to learn a new skill :)
If the PC doesn't have a serial port, check on the motherboard because
there
are sometimes serial port headers left unconnected by the PC manufacturer.
That's exactly in my case. Motherboard manual says the serial port
expansion is sold separately.
[..] Check with your Android mobile phone
what the GPS signal levels actually are in your possible locations - I
think
Apple don't allow you to access that information.
I don't have access to any Android device :( I'll try to use gpsmon or
other tool to check GPS signal level (S/N ratio of satellites should be
sufficient, I guess?).
The key here is to have some conducting magnetic material under the
antenna,
not just sitting on its own.
My GPS antenna hangs on the window handle and still gives the good result.
It's on the south facing window. Unfortunately, in the new location I will
have access only to west facing window.
Why is it good to have some conducting magnetic material under the antenna?
Is it to reduce multipath?
Best regards,
Adam
From: Didier Juges
It is my understanding that the latest version of the RPi (Pi4) has a
native full speed Ethernet interface, not through USB.
I also read that it needs a heat sink.
Didier KO4BB
---===
Didier,
It actually has a gigabit Ethernet, not connected over USB.
https://www.raspberrypi.org/magpi/raspberry-pi-4-specs-benchmarks/
The RPi-4 doesn't "need" a heatsink. It's design is intended to provide
high-performance bursts to improve the perceived speed - i.e. to create a
better user experience. It has throttling if the CPU temperature gets too
high, but it you need to run it continuously at full speed then you may need
a fan. A number of fans are available, for example:
https://shop.pimoroni.com/products/fan-shim
https://blog.pimoroni.com/raspberry-pi-4-thermals-and-fan-shim/
73,
David GM8ARV
SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
Adam Kumiszcza writes:
The key here is to have some conducting magnetic material under the
antenna, not just sitting on its own.
My GPS antenna hangs on the window handle and still gives the good result.
It's on the south facing window. Unfortunately, in the new location I will
have access only to west facing window.
You should orient it correctly so that it is facing up, not simply
dangling it from the cable. GPS antennas are directional.
Why is it good to have some conducting magnetic material under the antenna?
Is it to reduce multipath?
The GPS dielectric patch antennas are designed to perform best with a
ground plane. The optimum size varies a bit, but between 10…14cm in
diameter is about right. The ground plane does normally not need to
connect to anything, it has to be conductive but not necessarily
magnetic (aluminum foil is OK, too). If you have a magnetic puck
antenna, then using a magnetic surface has the advantage of the antenna
staying in place more easily, though (try the bottom of a large can of
vegetables). If you are unsure how large your ground plane really needs
to be, just use one of the programs that visualize the signal strength
on each sat in view and optimize for highest level over the visible part
of the sky, but especially the higher elevations (sats directly above
you).
Regards,
Achim.
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
Wavetables for the Waldorf Blofeld:
http://Synth.Stromeko.net/Downloads.html#BlofeldUserWavetables
You already have a PPS signal from your existing GPS, so I was thinking
simply of distributing that the the Windows PCs, and feeding it to the
serial port's DCD signal.
I will try that. I guess you can connect serial port directly to my
Uputronics expansion card (
https://store.uputronics.com/index.php?route=product/product&path=60_64&product_id=81)
while still attached to Raspberry Pi. Problem is, I'm a software, not a
hardware guy. No idea about soldering. Time to learn a new skill :)
If the PC doesn't have a serial port, check on the motherboard because
there
are sometimes serial port headers left unconnected by the PC manufacturer.
That's exactly in my case. Motherboard manual says the serial port
expansion is sold separately.
[..] Check with your Android mobile phone
what the GPS signal levels actually are in your possible locations - I
think
Apple don't allow you to access that information.
I don't have access to any Android device :( I'll try to use gpsmon or
other tool to check GPS signal level (S/N ratio of satellites should be
sufficient, I guess?).
The key here is to have some conducting magnetic material under the
antenna,
not just sitting on its own.
My GPS antenna hangs on the window handle and still gives the good result.
It's on the south facing window. Unfortunately, in the new location I will
have access only to west facing window.
Why is it good to have some conducting magnetic material under the antenna?
Is it to reduce multipath?
Best regards,
Adam
Adam,
Be aware that the signals from the Uputronics board (and similar) are most
likely to be at a 3.3V level, which /may/ not be sufficient to drive the DCD
pin on a traditional RS232 port, and you may need a level converter. You
don't need to connect the other lines - send & receive - just the DCD and
ground. I have a simple program which enables you to check for the pulsing
of the DCD line (and the other lines too):
https://www.satsignal.eu/software/net.htm#SerialPortLEDs
Yes, if you can use cgps or similar that would be fine - I just find the
phone handier!
The puck antennas are designed for use with a ground plane, and the maximum
pickup is then at 90 degrees to the ground-plane. I don't think that on
these cheap antennas there's any multipath reduction, just more gain from
having the ground plane. Be aware that in the new location the glass may
have some attenuation at 1.5 GHz as used by GPS.
Cheers,
David
SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
On Sun, Aug 11, 2019 at 8:01 PM Achim Gratz Stromeko@nexgo.de wrote:
Adam Kumiszcza writes:
The key here is to have some conducting magnetic material under the
antenna, not just sitting on its own.
My GPS antenna hangs on the window handle and still gives the good
result.
It's on the south facing window. Unfortunately, in the new location I
will
have access only to west facing window.
You should orient it correctly so that it is facing up, not simply
dangling it from the cable. GPS antennas are directional.
Why is it good to have some conducting magnetic material under the
antenna?
Is it to reduce multipath?
The GPS dielectric patch antennas are designed to perform best with a
ground plane. The optimum size varies a bit, but between 10…14cm in
diameter is about right. [...]
Thanks for all the info!
I've made a ca. 10.5 cm metal disc cut from an old car radio chasis and put
it under my gps antenna. It does not hang now, but lays on the window sill,
facing up.
I cannot see any difference between these positions. I've made 10
measurement for each position, getting 12 SNR values for satellites for
each measurement and then calculated the average of these.
Hanging antenna had 25.18 SNR average (2.21 standard deviation). Antenna on
a ground plane had 26.10 SNR average (2.08 standard deviation).
https://docs.google.com/spreadsheets/d/1lvGFTQS62MqiQALjHmWFZRY3hb5O1OqANFGBhnCaEUo/edit?usp=sharing
2 example screenshots from gpsmon included (before and after the change of
position)
If I take into account single high elevation satellite with good SNR
(satellite 26 in the examples), the new placement and ground plane even
lowered it :(
I guess the real benefit of the ground plane would be if the antenna was
outside, or my measurement method was wrong?
Best regards,
Adam
From: Adam Kumiszcza
[]
If I take into account single high elevation satellite with good SNR
(satellite 26 in the examples), the new placement and ground plane even
lowered it :(
I guess the real benefit of the ground plane would be if the antenna was
outside, or my measurement method was wrong?
Best regards,
Adam
---==
Adam,
My gut feeling is that is you're seeing just a 1 dB change, it /may/ not be
worth bothering with. On the other hand, don't throw dB away unnecessarily!
If the GPS can't "see" through the house (look at the polar plot), likely
tilting the puck down slightly (say 20 degrees) /might/ give a slight
benefit (higher gain for lower angle satellites). If you're seeing six,
say, satellites at a minimum - likely it's good enough.
Not sure this list approves of "good enough" - LOL!
Cheers,
David
SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
Adam Kumiszcza writes:
I've made a ca. 10.5 cm metal disc cut from an old car radio chasis and put
it under my gps antenna. It does not hang now, but lays on the window sill,
facing up.
That way you changed three variables in one go. You'd be better off
changing one single thing each time so you can see what changes cause
which results. You do have a patch antenna (rectangular flat shape),
not a quadrifilar helix, do you?
I cannot see any difference between these positions. I've made 10
measurement for each position, getting 12 SNR values for satellites for
each measurement and then calculated the average of these.
Looking at your gpsmon pictures you seem to see the low elevation sats
at very similar SNR as (most) high elevation ones. Any RF reflecting
things around in your neighbourhood? Also, as David already mentioned,
thermo-pane windows are actually damping RF quite significantly and even
reflect them at low incidence angles. You might try a few minutes with
an open window and otherwise unchanged antenna location to see what
happens.
Hanging antenna had 25.18 SNR average (2.21 standard deviation). Antenna on
a ground plane had 26.10 SNR average (2.08 standard deviation).
The constellation providing your fix (four satellites minimum) should
probably all be well over 30dB, peaking in the mid 40dB SNR range.
If I take into account single high elevation satellite with good SNR
(satellite 26 in the examples), the new placement and ground plane even
lowered it :(
You may have to experiment with antenna position a bit more. I have
seen more than 15dB changes from rather small changes in antenna
placement. It's definitely worth experimenting a bit to find one that
is good over the full cycle of the GPS constellation.
I guess the real benefit of the ground plane would be if the antenna was
outside, or my measurement method was wrong?
No, the ground plane (if your antenna needs one, not all do) is there to
improve the gain in the forward direction and make the elevation pattern
more uniform. Outside oir inside doesn't matter, but antennas are
influenced by many things in their near-field region (at around 1.5GHz,
a few wavelengths at most, so ~30…50cm). Again, you may be too close to
the window pane for instance.
Regards,
Achim.
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
Factory and User Sound Singles for Waldorf rackAttack:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds
On Mon, Aug 12, 2019 at 10:14 PM Achim Gratz Stromeko@nexgo.de wrote:
Adam Kumiszcza writes:
I've made a ca. 10.5 cm metal disc cut from an old car radio chasis and
put
it under my gps antenna. It does not hang now, but lays on the window
sill,
facing up.
That way you changed three variables in one go. You'd be better off
changing one single thing each time so you can see what changes cause
which results. You do have a patch antenna (rectangular flat shape),
not a quadrifilar helix, do you?
It's a normal patch antenna, bought together with gps addon card:
https://store.uputronics.com/index.php?route=product/product&path=60_65&product_id=67
After all your tips I just checked whether the roof itself blocks the
signal or not. I put the patch antenna together with a metal disk on top of
a high wardrobe, close to ceiling, and I guess it is the best position
here. See attached screenshots.
On Mon, Aug 12, 2019 at 5:01 PM David J Taylor via time-nuts <
time-nuts@lists.febo.com> wrote:
My gut feeling is that is you're seeing just a 1 dB change, it /may/ not
be
worth bothering with. On the other hand, don't throw dB away
unnecessarily!
[..] If you're seeing six,
say, satellites at a minimum - likely it's good enough.
I didn't have to stick to "good enough", David :)
Unfortunately, I will have to move this ntp server to another location (or
make another one and leave this one here). It will not have access to south
facing window there, only west is possible.
Best regards,
Adam
