Raspberry Pi GPS Stratum 1 NTP Server

[Tobi2707]

After setting the reset command still no fix or something:(

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pi@raspberrypi ~ $ ntpq -pn
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 127.127.22.0    .PPS0.           1 l    -    8    0    0.000    0.000   0.000
 127.127.20.0    .GPS0.           1 l    -    8    0    0.000    0.000   0.000

[Tobi2707]

Any news so far?
Did you received your new Pi and the GPS HAT?:)

[gtj]

Any news so far?
Did you received your new Pi and the GPS HAT?:)

Yep, I got them both yesterday and I think I have a configuration that works. I let it run overnight and it seems to be stable so I'm going to write it up this morning.

[Tobi2707]

Okay that's very nice:) I Hope this will fix the problem :)
So it World be nice of you can write something like a tutorial:)

[gtj]

Ok, Here's the process.

• Start with a fresh Raspian SD card.
• In the initial configuration menu...
  • select Expand Filesystem.
  • select Advanced, SSH and enable it.
  • select Advanced, Serial, Answer No for a login shell.
  • select Finish and reboot.
• Immediately after reboot...

  • Code: Select all

    $ sudo apt-get update
    $ sudo apt-get dist-upgrade
    $ sudo rpi-update
    $ sudo apt-get install libcap-dev libssl-dev pps-tools
    

  • Add dtoverlay=pps-gpio,gpiopin=4 to the end of /boot/config.txt
  • Add pps-gpio to the end of /etc/modules
  • Reboot
  • After the reboot verify that /dev/pps0 exists.
• Build and Install NTP...

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    $ cd /usr/src
    $ sudo mkdir ntp
    $ chown pi:pi ntp
    $ cd ntp
    $ wget http://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-4.2/ntp-4.2.8p1.tar.gz
    $ tar -xzf ntp-4.2.8p1.tar.gz
    $ cd ntp-4.2.8p1
    $ ./configure --enable-all-clocks --enable-parse-clocks --disable-local-libopts --enable-step-slew --without-ntpsnmpd --enable-linuxcaps --prefix=/usr
    $ make -j5
    $ sudo apt-get remove ntp
    $ sudo apt-get install ntpdate
    $ sudo make install
    

  • Edit /etc/ntp.conf and adjust it as follows...

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    # pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
    # pick a different set every time it starts up.  Please consider joining the
    # pool: <http://www.pool.ntp.org/join.html>
    server 0.debian.pool.ntp.org iburst
    #server 1.debian.pool.ntp.org iburst
    #server 2.debian.pool.ntp.org iburst
    #server 3.debian.pool.ntp.org iburst
    
    server 127.127.20.0 mode 84 minpoll 3 iburst prefer
    fudge 127.127.20.0 stratum 1 flag1 1 flag2 0 flag3 0 flag4 0 time1 0.0 time2 0.280 refid GPS0
    
    # Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
    # details.  The web page <http://support.ntp.org/bin/view/Support/AccessRestrictions>
    # might also be helpful.
    

  • Delete /etc/dhcp/dhclient-exit-hooks.d/ntp to prevent dhcp from overwriting the ntp config.
  • Create the file /etc/udev/rules.d/99-gps.rules with the following contents...

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    KERNEL=="pps0",SYMLINK+="gpspps0"
    KERNEL=="ttyAMA0", SYMLINK+="gps0"
    

  • Run sudo udevadm trigger to create symlinks /dev/gps0 and /dev/gpspps0
• Download and Install gps-tools

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    $ cd /usr/src
    $ sudo mkdir gps-tools
    $ sudo chown pi:pi gps-tools
    $ cd gps-tools
    $ wget https://github.com/f5eng/mt3339-utils/archive/gps.zip
    $ unzip gps.zip
    $ cd mt3339-utils-gps
    $ sudo cp epoinfo epoloader eporetrieve gpsinit gpssend gpsstatus /usr/local/bin/
    $ sudo cp *.conf /etc/
    

• Test GPS
  • Run sudo ppstest /dev/pps0. You should see timestamp every second. CTRL-C to exit.
  • Run gpsinit -s 115200 -f /etc/gpsinit_nav.conf /dev/ttyAMA0 to initialize the GPS unit for testing
  • Run gpsstatus /dev/ttyAMA0. Do you get a GPS or DGPS fix within 10 minutes? If not,
    Read the README at https://github.com/f5eng/mt3339-utils for instructions on how to initialize
    the GPS unit and why it's important.
• Set up the GPS Unit for timekeeping
  • Run gpsinit -s 115200 -f /etc/gpsinit_time.conf /dev/ttyAMA0 to initialize the GPS unit
• Start and test ntpd

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    $ sudo update-rc.d ntp defaults
    $ sudo service ntp start
    $ sudo ntpq -pn
    

  • If the ppstest previously passed, you should eventually see...

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         remote           refid      st t when poll reach   delay   offset  jitter
    ==============================================================================
    oGPS_NMEA(0)     .GPS0.           1 l    1    8  377    0.000    0.001   0.004
     xx.xx.xx.xx     PPS(1)           2 u    2    8  377    0.398   -0.072   0.212
    

  • The 'o' in the first column indicated that ntp is using the GPS for time.
• Notes:
  • If you're Pi isn't network connected, you can set the system clock directly from the gps using the gpsinit command as long as ntpd isn't running.

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    $ gpsinit -s 115200 -i set_system_clock /dev/ttyAMA0
    

    To do this at startup, edit /etc/rc.local and add the following lines at the bottom before the final 'exit 0'

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    service ntp stop
    /usr/local/bin/gpsinit -s 115200 -i set_system_clock /dev/ttyAMA0
    service ntp start
    

[Tobi2707]

At first thank you for your How-To:)
So i tried to follow your tutorial and i got till the point ‚Test GPS‘, but first i have some notes in my case:

Ok, Here's the process.

-Add dtoverlay=pps-gpio,gpiopin=18 to the end of /boot/config.txt
-Add pps-gpio to the end of /etc/modules

Sure that it's pin 18? You also have the Ultimate GPS HAT? Shouldn't it be pin 4? With pin 4 i get the new line every second running ppstest /dev/pps0 .

Build and Install NTP...

• Code: Select all

  1 $ cd /usr/src
  2 $ mkdir ntp
  3 $ cd ntp
  4 $ wget http://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-4.2/ntp-4.2.8p1.tar.gz
  5 $ tar -xzf ntp-4.2.8p1.tar.gz
  6 $ cd ntp-4.2.8p1.tar.gz
  7 $ ./configure --enable-all-clocks --enable-parse-clocks --disable-local-libopts --enable-step-slew --without-ntpsnmpd --enable-linuxcaps --prefix=/usr
  8 $ make -j5
  9 $ sudo apt-get remove ntp
  10 $ sudo make install
  

I'm logged in as pi so I have no permission to write in this folder. So I have to use 'sudo' in line 2, 4, 5, 7, 8 ?
And I think line 6 should be: '$ cd ntp-4.2.8p1' without the .tar.gz?
It should be said that you only use 'make -j5' if you're using a RPi 2, with and RPI B+ it's just 'make'.
So the final folder for the make command should be: /usr/src/ntp/ntp-4.2.8p1 ?

[*] Edit /etc/ntp.conf and adjust it as follows...

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# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server 0.debian.pool.ntp.org iburst noselect
#server 1.debian.pool.ntp.org iburst
#server 2.debian.pool.ntp.org iburst
#server 3.debian.pool.ntp.org iburst

server 127.127.20.0 mode 84 minpoll 3 iburst prefer
fudge 127.127.20.0 stratum 1 flag1 1 flag2 0 flag3 0 flag4 0 time1 0.0 time2 0.280 refid GPS0

# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details.  The web page <http://support.ntp.org/bin/view/Support/AccessRestrictions>
# might also be helpful.

Are you sure that mode 84 is right? And if so, whats the difference to 88?

Run sudo udevadm trigger to create symlinks /dev/gps0 and /dev/gpspps0[/list]

Is it right that i don’t get an response output here?

Test GPS
1. Run sudo ppstest /dev/pps0. You should see timestamp every second. CTRL-C to exit.
2. Run gpsinit -s 115200 -f /etc/gpsinit_nav.conf /dev/ttyAMA0 to initialize the GPS unit for testing
3. Run gpsstatus /dev/ttyAMA0. Do you get a GPS or DGPS fix within 10 minutes? If not,
Read the README at https://github.com/f5eng/mt3339-utils for instructions on how to initialize
the GPS unit and why it's important.

Point 1 does works, but i got an error with point 2:

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pi@raspberrypi ~ $ gpsinit -s 115200 -f /etc/gpsinit_nav.conf /dev/ttyAMA0
Making sure the unit is in NMEA mode
Making sure the speeds match
Traceback (most recent call last):
  File "/usr/local/bin/gpsinit", line 293, in <module>
    sys.exit(main() or 0)
  File "/usr/local/bin/gpsinit", line 263, in main
    fg = get_known_state(args.output_device, args.speed, None, False)
  File "/usr/local/bin/gpsinit", line 227, in get_known_state
    resp = send_and_wait(fg, "PMTK000", 5)
  File "/usr/local/bin/gpsinit", line 97, in send_and_wait
    thread = rx_loop_thread(fg)
TypeError: __init__() takes exactly 3 arguments (2 given)

This error als appears when im running the factory reset command, so i can't set it back to factory state.

So i can’t go on, but it is almost done:)

[gtj]

At first thank you for your How-To:)
So i tried to follow your tutorial and i got till the point ‚Test GPS‘, but first i have some notes in my case:
Sure that it's pin 18? You also have the Ultimate GPS HAT? Shouldn't it be pin 4? With pin 4 i get the new line every second running ppstest /dev/pps0 .

Yes. Pin 4 on the hat is actually wired to GPIO 18 on the Pi.

I'm logged in as pi so I have no permission to write in this folder. So I have to use 'sudo' in line 2, 4, 5, 7, 8 ?
And I think line 6 should be: '$ cd ntp-4.2.8p1' without the .tar.gz?
It should be said that you only use 'make -j5' if you're using a RPi 2, with and RPI B+ it's just 'make'.
So the final folder for the make command should be: /usr/src/ntp/ntp-4.2.8p1 ?

Ah, I forgot about that. Rather than doing 'sudo' for each line, you can do the following...

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$ cd /usr/src
$ sudo mkdir ntp
$ sudo chown pi:pi ntp
$ cd ntp

That'll make you the owner of the directory. You'll still need to use sudo for the 'make install'.
Correct on the other points.

Are you sure that mode 84 is right? And if so, whats the difference to 88?

Yes. 80 is the mode for 115200 baud. Adding 4 causes ntp to use the GPGLL sentence (the first one output). Adding 8 says to use GPZDA. Turns out GPGLL is better aligned to the PPS pulse.

Is it right that i don’t get an response output here?

Correct. The links should have been created though.

Point 1 does works, but i got an error with point 2:

Code: Select all

pi@raspberrypi ~ $ gpsinit -s 115200 -f /etc/gpsinit_nav.conf /dev/ttyAMA0
Making sure the unit is in NMEA mode
Making sure the speeds match
Traceback (most recent call last):
  File "/usr/local/bin/gpsinit", line 293, in <module>
    sys.exit(main() or 0)
  File "/usr/local/bin/gpsinit", line 263, in main
    fg = get_known_state(args.output_device, args.speed, None, False)
  File "/usr/local/bin/gpsinit", line 227, in get_known_state
    resp = send_and_wait(fg, "PMTK000", 5)
  File "/usr/local/bin/gpsinit", line 97, in send_and_wait
    thread = rx_loop_thread(fg)
TypeError: __init__() takes exactly 3 arguments (2 given)

This error als appears when im running the factory reset command, so i can't set it back to factory state.

So i can’t go on, but it is almost done:)

Oops. That's a bug. I can correct that pretty quickly. Give me about 30 minutes.

[gtj]

Ok, I fixed the bug in gpsinit. Re-download https://github.com/f5eng/mt3339-utils/archive/gps.zip and install it and you should be good to go.

[Tobi2707]

Thanks:)
Something to delete before?
And the RPi was shut down, does this matter?

[gtj]

Oh, you were absolutely correct on the pin being 4. I was confused. So it should be "dtoverlay=pps-gpio,gpiopin=4".

[gtj]

Thanks:)
Something to delete before?
And the RPi was shut down, does this matter?

Nothing to delete, just recopy the files.
No issue with the Pi shutting down.

[Tobi2707]

Now i got this error:

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pi@raspberrypi ~ $ gpsinit -s 115200 -f /etc/gpsinit_nav.conf /dev/ttyAMA0
Making sure the unit is in NMEA mode
Making sure the speeds match
The GPS speed and the port speed couldn't be synchronized.
Retrying
Making sure the speeds match
The GPS speed and the port speed couldn't be synchronized.

[gtj]

Just try it a few times.

[Tobi2707]

How often?:P
i tried it 10 times and still same error :(

Maybe something went wrong during recopy?

[gtj]

You're sure ntpd isn't running? Can you do the 'gpsstatus /dev/ttyAMA0'?