NTP

Whilst it is easy to get a fairly decent NTP clock reference - I wondered about building my own.

Parts

• Orange Pi
  • OrangePi One
• GPS Chip
  • NEO6
• 4 Jumper Leads M/F

Build OS

After several attempts to configure the OragePi - the OS is the probem not the hardware. I used armbian in the end. No matter whoch OS you choose you will have to do these steps.

- Build OS
- Change Machine Name
- Set Static IP Address
- Setup UART access
- Test NMEA Output
- Install GPSD
- Install NTP

That sounds like a lot of stuff - but the most difficult is Setup UART Access. I could not accomplish this on Ubuntu. Hence I switched to Armbian (which was the 1st time I had used the OS - but it seems very well done - and easy to use).

All OS installs were command line only - No GUI !!

So with the OS setup... I moved onto the GPS chip.

GPS Chip

Pinout for the Orange Pi

GPS Chip Pins

The GPS chip has 4 connections, but as we do not send data to the GPS chip.. I did not connect the RX (on GPS) pin.

OS Software

With the GPS Wires to the OrangePi, I then rebooted - checled the voltage with a Multi-Meter - looked ok. And then tried to understand why I could not see any data.

The problem is that I am using UART3 pin conections - so I need to enable UART3 in the boot config process.

Warning: This is OS specific I could not find a way to accomplish this using Ubuntu, so I switched to armbian - with a little tweaking I was then able to enable uart3 (armbian-config -> System -> Hardware).

Verify you have data

cat /dev/ttyS3

And I see NMEA Sentances.

$GPGSV,3,2,12,12,08,213,30,13,79,012,28,15,57,255,24,20,33,040,24*74

$GPGSV,3,3,12,24,15,192,17,25,00,244,25,29,34,303,18,30,17,063,31*71

$GPGLL,1509.56255,N,12041.76433,E,031417.00,A,A*66

$GPRMC,031418.00,A,1509.56262,N,12041.76423,E,0.344,,190922,,,A*77

$GPVTG,,T,,M,0.344,N,0.638,K,A*2D

$GPGGA,031418.00,1509.56262,N,12041.76423,E,1,10,0.92,31.2,M,36.9,M,,*6F

$GPGSA,A,3,06,29,15,05,12,30,20,02,13,11,,,1.65,0.92,1.37*00

$GPGSV,3,1,12,02,57,353,17,05,39,351,24,06,25,118,21,11,51,090,34*75

$GPGSV,3,2,12,12,08,213,30,13,79,012,28,15,57,255,25,20,33,040,24*75

$GPGSV,3,3,12,24,15,192,17,25,00,244,25,29,34,303,18,30,17,063,30*70

$GPGLL,1509.56262,N,12041.76423,E,031418.00,A,A*6C

GPSD Setup

There really is no point in installing gpsd until you can see the NMEA data. That is the #1 priority.

sudo apt install gpsd gpsd-clients

Then

vi /etc/default/gpsd

This is what mine looks like

DEVICES="/dev/ttyS3"
START_DAEMON="true"
# Other options you want to pass to gpsd
GPSD_OPTIONS="-n"

# Automatically hot add/remove USB GPS devices via gpsdctl
USBAUTO="false"

Now enable the gpsd service and check it is running

systemctl enable gpsd.service     #This adds the service
systemctl start  gpsd.service     #Manually start
systemctl status gpsd.service     #check it is running

The service should auto start .. so we can reboot to check that

sync && reboot -h now

Viewing the GPS Data

There are two useful utilities

• cgps -s -u m.
• gpsmon

These are command line (as there is no screen) on this device.

Lack of PPS

The Gps module I bought was a NEO-6, it only has 4 wires connecting it... and there is no PPS (pulse per second) feature.

I am therefore unsure if this will add accuracy to my NTP process.

NTP

Installed with

apt-get install ntp

As I only have a GPS feed and not a PPS as well - I can only add 1 source

Place these lines in /etc/ntp.conf

# gpsd clock via shm
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 refid GPS flag1 1

And restart ntp

systemctl restart ntp.service

To see if our GPS feed is being used (xSHM) [accessed via shared memory].

ntpq -p

  remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
xSHM(0)          .GPS.            0 l    -   16  377    0.000   -7.059   2.269
 0.ubuntu.pool.n .POOL.          16 p    -   64    0    0.000   +0.000   0.001
 1.ubuntu.pool.n .POOL.          16 p    -   64    0    0.000   +0.000   0.001
 2.ubuntu.pool.n .POOL.          16 p    -   64    0    0.000   +0.000   0.001
 3.ubuntu.pool.n .POOL.          16 p    -   64    0    0.000   +0.000   0.001

The important figure to look at is the Jitter... the GPS source is quite low.... which means it should be having a good effect on the time source.

Next Steps

• More Accuracy. -Either get another gps with PPS - this could be added to the same OrangePi, so there are two sources.
• Use the NTP Internally
  • On my main development servers I have pointed them to use bigben