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pi-time

Raspberry PI Stratum 1 server

Raspberry Pi Installation script

Bash script automating the installation of a GPS / PPS Disciplined Stratum-1 Server on the Raspberry Pi (3), 4, or 5

Design principles:

  • Dedicated to being a Stratum-1 NTP server
  • Use a GPS Breakout board

Known issues:

  • None so far
  • Should work on a Pi Zero, but as these have no ethernet cable, and NTP over wireless is less than optimal it's untested
  • May work on a Raspberry Pi 2, haven't tried.

Latest changes

2023-12-28 - version 5.01

  • Settings in .env-file
  • ntpstats and logging corrected
  • ntpleapfetch usage in update-leap.service

2023-12-27 - Raspberry Pi OS (64-bit) Lite (Debian 12, codename: Bookworm)

  • Version 5 for Raspberry PI OS Lite (64 bit) - Debian 12 (Bookworm)
  • This script will only work with ntpsec and has only been tested on the Debian 12 (Bookworm) version of RaspberryPi OS

2021-12-02 - Raspberry Pi OS (64-bit) Lite

  • Tested to work with Raspberry Pi OS (64-bit) Lite

2021-12-02 - Bullseye version

  • Version 4.00 now for Debian 11 (Bullseye)

2021-12-05 - 1GHz

  • Pinned clock frequency at 1GHz - seems to give best precision, anything below that is -19 instead of -20 at 1GHz

2021-12-10 - config.txt include ntpserver.txt

  • Keeping the original config.txt, only adding include ntpserver.txt

Installation

Prerequisite: A Raspberry PI 4 or 5 and an SD-CARD

  • Download the latest Raspberry Pi OS Lite here: https://downloads.raspberrypi.org/raspios_lite_armhf/images/raspios_lite_armhf-2021-11-08/2021-10-30-raspios-bullseye-armhf-lite.zip
  • Write the latest Raspberry Pi OS Lite, based on Debian 12 (Bookworm), to a good quality sd-card using rpi-imager, dd or whatever tool you prefer. Using rpi-imager is the easiest option, allowing you to create credentials for initial logon and set hostname
  • Configure the .env to your wishes, do NOT forget to change the SSH Public Key and whether or not to disable the original user (which used to be "pi")
  • Run prep_sd.sh, enter a new hostname for the pi1.
  • Boot the Pi, logon as the credentials created with rpi-imager (this use will be disabled later, if correctly named in .env, I use "ntp" as user)
  • sudo su -
  • run ./install-rpi-stratum1.sh
  • Watch install progress on the tty, and from another SSH session, run tail -fn1000 /var/log/syslog | grep 'Stratum1 NTP Server'
  • After reboot the Pi should now provide good time, however give it time :) lots of time to achieve good precision
  • Login with root (if you added your public ssh key to .env). If not login with the user you created earlier with rpi-imager.

1 prep_sd.sh prepares the SD-Card enabling SSH, copies the install script, and changes hostname on the sd-card.

Hardware

It's easy to find GPS breakout boards for Arduino or Raspberry Pi's on ebay, amazon, and other semi-dubious marketplaces. However there's also great boards from Adafruit and others.

  • Make sure the board outputs the PPS signal.
  • The serial I/O and PPS must be 3.3v TTL level serial. If it's 5 volt serial, then level shifting is needed, however
  • some boards can be supplied with 5v and still only outputs 3v3.
  • 5v output will kill the GPIO on the Raspberry Pi. Start with powering the GPS Board with 3v3 and see if that works.
  • Connect the ground of the GPS module to pin 6 (Ground) of the GPIO header on the Raspberry Pi.
  • Connect either a +5 power input to pin 2 (or pin 4) of the GPIO header (see above for 5v warning), or
  • +3v3 power input to pin 1 (or pin 17) of the GPIO header.
  • Connect the serial input (RXD) of the GPS module to pin 8 of the GPIO header. This is the UART TXD on the Raspberry Pi2.
  • Connect the serial output (TXD) to pin 10 of the GPIO header. This is the UART RXD on the Raspberry Pi2.
  • Connect the PPS signal to pin 12 (GPIO 18) of the GPIO header.

2 When configured with enable_uart=1 in /boot/config.txt. The install-script does this in configure_pps.

GPIO Pinout from raspberrypi.org

drawing

Below is a picture of GPS board I've used several of for exactly this purpose (lucky to buy 7 for a great price).

alt text

Tips and tricks for troubleshooting

Check syslog for 'finalized installation of stratum-1 server', then at least the script finished, but there should also be a log entry for each routine called (main)

Follow the log during installation

  • tail -fn1000 /var/log/syslog | grep 'Stratum1 NTP Server'

Verify pps

  • dmesg | grep pps
  • ppstest /dev/pps0
  • ppswatch -a /dev/pps0

Run gpsd manually (stop gpsd.socket first)

  • gpsd -D 5 -N -n /dev/ttyAMA0 /dev/pps0 -F /var/run/gpsd.sock
  • systemctl stop gpsd.*
  • killall -9 gpsd Reconfigure gpsd
  • dpkg-reconfigure -plow gpsd

Check GPS reception and ensure that it outputs to NTP

  • cgps -s
  • gpsmon
  • ipcs -m
  • ntpshmmon

Monitoring the ntp daemon

  • ntpq -crv -pn
  • watch -n 10 'ntpstat; ntpq -p -crv; ntptime;'
  • watch -n 10 'hostname -s; echo -----------; ntpstat; ntpq -p -crv; ntptime;'

or if using Chrony

  • watch -n5 'hostname -s; echo --------; chronyc sources -v; chronyc tracking;'

If HW clock installed

  • dmesg | grep rtc
  • hwclock --systohc --utc
  • hwclock --show --utc --debug
  • cat /sys/class/rtc/rtc0/date
  • cat /sys/class/rtc/rtc0/time
  • cat /sys/class/rtc/rtc0/since_epoch
  • cat /sys/class/rtc/rtc0/name
  • i2cdetect -y 1

Update system

  • export DEBIAN_FRONTEND=noninteractive; apt update; apt full-upgrade -y;