Raspberry Pi Time Server

Stratum 1 GNSS NTP Server running on a Raspberry Pi 2

Equipment

These are the parts I have used.

• Raspberry Pi 2
• SparkFun ublox NEO-M9N
  • This Adafruit module is a good alternative
• Adafruit DS3231 RTC
• Some cheap Active GPS Antenna
• uFL to SMA Adapter Pigtail (Example)
• Pin Headers for the GNSS module (Soldering required)
• Some Male-to-Female DuPont Cables

Previously the BeagleBone Black SBC was used, check the beaglebone branch for more information.

Setup

1. Install packages:

sudo apt update
sudo apt install pps-tools chrony nginx php-fpm php-gd

On trixie, build GPSd 3.27.x from the forky source package. Trixie currently ships GPSd 3.25, while forky/sid have GPSd 3.27.x.

Fetch the Debian 13/trixie archive signing key first. Forky source metadata is signed by Debian's archive key, not Raspberry Pi OS's archive key.

sudo dpkg -r gpsd-build-deps

sudo apt install ca-certificates wget
sudo install -d -m 0755 /usr/share/keyrings
sudo wget -O /usr/share/keyrings/debian-archive-trixie-automatic.asc https://ftp-master.debian.org/keys/archive-key-13.asc

sudo tee /etc/apt/sources.list.d/debian-forky.sources >/dev/null <<'EOF'
Types: deb-src
URIs: http://deb.debian.org/debian
Suites: forky
Components: main
Signed-By: /usr/share/keyrings/debian-archive-trixie-automatic.asc
EOF

sudo apt update
sudo apt install build-essential scons pkgconf python3 python-is-python3 python3-serial libncurses-dev libusb-1.0-0-dev libsystemd-dev libudev-dev
apt source gpsd/forky
cd gpsd-3.27.*

scons -c
scons prefix=/usr systemd=yes manbuild=no qt=no dbus_export=no
sudo scons prefix=/usr systemd=yes manbuild=no qt=no dbus_export=no install
sudo scons prefix=/usr systemd=yes manbuild=no qt=no dbus_export=no udev-install

if ! getent passwd gpsd >/dev/null; then
  sudo adduser --system --no-create-home --home /run/gpsd --ingroup dialout gpsd
fi
sudo adduser gpsd dialout
gpsd -V

2. Edit /boot/firmware/config.txt

• Uncomment dtparam=i2c_arm=on

• Add the following under [all]:

  enable_uart=1
  dtoverlay=i2c-rtc,ds3231
  dtoverlay=pps-gpio,gpiopin=18

3. Edit /boot/firmware/cmdline.txt, remove console=serial0,115200, add nohz=off.

4. Reboot to apply changes.

5. Setup GPSd

• Edit /etc/default/gpsd. Use file in this repo as reference.

• Edit systemd service to start after chrony: sudo systemctl edit gpsd

  Add:

  [Unit]
  Wants=chrony.service
  After=chrony.service
  

• Start GPSd:

  sudo systemctl disable --now serial-getty@ttyAMA0.service
  sudo systemctl mask serial-getty@ttyAMA0.service
  sudo systemctl enable --now gpsd
  systemctl status gpsd

• Check using the cgps command.

6. Setup Chrony

• Edit Chrony config files. Use file in this repo as reference.

• Start Chrony:

  sudo systemctl enable chrony
  sudo systemctl restart chrony gpsd
  systemctl status chrony

• Check using chronyc tracking, chronyc sources -v, and chronyc sourcestats -v commands.

7. (Optional) Setup nginx + php to serve webpage: /etc/nginx/ & /var/www/html.

Webpage

The following webpages are included in this repo.

index.html

Shows current time + offset, similar to time.is (Requires serverDate.js.php).

chrony.php

Quick page that shows the output of the following commands: chronyc sources, chronyc sourcestats, chronyc tracking.

References

My setup is based off the following guides.

• https://austinsnerdythings.com/2021/04/19/microsecond-accurate-ntp-with-a-raspberry-pi-and-pps-gps/
• https://robrobinette.com/pi_GPS_PPS_Time_Server.htm
• http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html
• https://conorrobinson.ie/raspberry-pi-ntp-server-part-6/