+#+TITLE: Ninfacyzga-1 Time Tracking
+#+AUTHOR: Steven Baltakatei Sandoval
+#+EMAIL: baltakatei@gmail.com
* Time Tracking
+** About
This document was created by Steven Baltakatei Sandoval on
~2020-07-23T22:27Z~ under a [[https://creativecommons.org/licenses/by-sa/4.0/][Creative Commons BY-SA 4.0 license]]. It
-was updated by Steven Baltakatei Sandoval on ~2020-10-13T18:02Z~
-
-** Development Task list
-*** Set up prototype unit
-**** DONE Solder wire for PPS signal
-***** 2020-07-25T20:03Z; bktei> Soldered pins to permit accessibility.
- CLOSED: [2020-07-25 Sat 20:03]
-**** Follow guide
-- [[https://ozzmaker.com/forums/topic/connecting-gps-pps-pin/][Ozzmaker post]] on ~PPS~ wiring and a [[https://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html][guide]] recommendation.
-- [[http://www.satsignal.eu/raspberry-pi/Schmidt-RPZ-NTP-2016.pdf][Schmidt article]] on Raspberry Pi Zero time server.
-- [[https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html][GPSD dev ref]] page for ~gpsd~ interfacing with ~ntp~.
-- [[https://raspberryautomation.com/connect-multiple-ds18b20-temperature-sensors-to-a-raspberry-pi/][Raspberry Autom]] article on specifying custom GPIO pin.
-*** Document prototype unit
-**** Summarize setup steps
-***** Perform main setup steps
-***** Install time-specific apps
-: $ sudo apt install usbmount eject gpsd gpsd-clients python-gps pps-tools ntp
-
-Explanation:
-
-- ~python-gps~: (Add explanation here)
-- ~pps-tools~: Package containing ~ppstest~ command useful for
- checking status of PPS devices.
-- ~ntpsec~: Security-hardened version of ~ntp~, the Network Time
- Protocol package. Useful for automatically setting the system clock
- according to time servers or local hardware.
-
-
-**** TODO Integrate DHCP details from gregledet tutorial
-http://www.gregledet.net/computers/building-a-stratum-1-ntp-server-with-a-raspberry-pi-4-and-adafruit-ultimate-gps-hat/
-**** TODO Note working ntp.conf file
-
-#+BEGIN_EXAMPLE
-# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help
-
-driftfile /var/lib/ntp/ntp.drift
-logfile /var/log/ntp.log
-
-# Leap seconds definition provided by tzdata
-leapfile /usr/share/zoneinfo/leap-seconds.list
-
-# Enable this if you want statistics to be logged.
-statsdir /var/log/ntpstats/
-
-statistics loopstats peerstats clockstats
-filegen loopstats file loopstats type day enable
-filegen peerstats file peerstats type day enable
-filegen clockstats file clockstats type day enable
-
-
-# You do need to talk to an NTP server or two (or three).
-#server ntp.your-provider.example
-server time.nist.gov iburst minpoll 5 maxpoll 5
-server tick.usno.navy.mil iburst minpoll 5 maxpoll 5
-server 0.us.pool.ntp.org iburst minpoll 5 maxpoll 5
-server 0.us.pool.ntp.org iburst minpoll 5 maxpoll 5
-server 0.us.pool.ntp.org iburst minpoll 5 maxpoll 5
-server 0.us.pool.ntp.org iburst minpoll 5 maxpoll 5
-
-# 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>
-#pool 0.debian.pool.ntp.org iburst
-#pool 1.debian.pool.ntp.org iburst
-#pool 2.debian.pool.ntp.org iburst
-#pool 3.debian.pool.ntp.org iburst
-
-# PPS Kernel mode
-server 127.127.22.0 minpoll 4 maxpoll 4 true
-fudge 127.127.22.0 flag3 1 refid kPPS
-
-# GPS PPS reference (NTP2)
-server 127.127.28.2 minpoll 4 maxpoll 4
-fudge 127.127.28.2 refid SHM2
-
-# GPS Serial data reference (NTP0)
-server 127.127.28.0 minpoll 4 maxpoll 4 prefer
-fudge 127.127.28.0 time1 +0.593 refid GPS
-
-# Fix False tickers
-tos mindist 0.5
-
-# 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.
-#
-# Note that "restrict" applies to both servers and clients, so a configuration
-# that might be intended to block requests from certain clients could also end
-# up blocking replies from your own upstream servers.
-
-# By default, exchange time with everybody, but don't allow configuration.
-restrict -4 default kod notrap nomodify nopeer noquery limited
-restrict -6 default kod notrap nomodify nopeer noquery limited
-
-# Local users may interrogate the ntp server more closely.
-restrict 127.0.0.1
-restrict ::1
-
-# Needed for adding pool entries
-restrict source notrap nomodify noquery
-
-# Clients from this (example!) subnet have unlimited access, but only if
-# cryptographically authenticated.
-#restrict 192.168.123.0 mask 255.255.255.0 notrust
-
-
-# If you want to provide time to your local subnet, change the next line.
-# (Again, the address is an example only.)
-#broadcast 192.168.123.255
-
-# If you want to listen to time broadcasts on your local subnet, de-comment the
-# next lines. Please do this only if you trust everybody on the network!
-#disable auth
-#broadcastclient
-#+END_EXAMPLE
-
-**** TODO Integreate References
-- Some explanations for ~time1~, ~flag1~, ~flag3~, ~refid~, etc. strings in ntp.conf: [[http://doc.ntp.org/4.2.8/drivers/driver28.html][link]].
-- NTP Basics (what "system peer" means): [[https://kb.meinbergglobal.com/kb/time_sync/ntp/ntp_basics][link]].
-- GPSD guide indicating PPS signals should be preferred over GPS signals: [[https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html#_feeding_ntpd_from_gpsd][link]]
+was updated by Steven Baltakatei Sandoval on ~2020-10-16T22:26Z~
** Narrative
The ~ninfacyzga-01~ device is equipped with an Ozzmaker BerryGPS-IMU
-module which provides time and location data to ~gpsd~ and ~ntp~. The
+module which provides time and location data to ~gpsd~ and ~ntpsec~. The
time is provided by GPS satellites which themselves are
equipped [fn:nasa_20020408_atomicclock] with atomic clocks. This
extremely accurate set of clocks are needed since a GPS receiver
** Description
*** Hardware
-Ozzmaker BerryGPS-IMU, Version 3
+Ozzmaker BerryGPS-IMU, Version 3 (see [[https://ozzmaker.com/berrygps-berrygps-imu-quick-start-guide/][ref]]).
*** Software
-This guide describes steps that may be used to convert a Raspberry Pi
-into a time server using ~gpsd~.
+- [[https://tracker.debian.org/pkg/gpsd][~gpsd~]] : A background daemon app capable of interfacing with the
+ [[https://ozzmaker.com/berrygps-berrygps-imu-quick-start-guide/][Ozzmaker BerryGPS-IMU]]'s GPS submodule. Installed and initialized by
+ ~apt~. Should be installed along with the ~gpsd-clients~
+ package. This procedure was developed with ~gpsd~ version
+
+- [[https://tracker.debian.org/pkg/ntpsec][~ntpsec~]] : A security-hardned version of [[https://tracker.debian.org/pkg/ntp][~ntp~]] which is a "[[https://en.wikipedia.org/wiki/Network_Time_Protocol][Network
+ Time Protocol]]" app that synchronizes the system clock with local or
+ remote time servers or devices. It is capable of extracting time
+ data from a GPS signal handled by ~gpsd~. It is also capable of
+ using the high precision PPS (pulse-per-second) signal handled by
+ ~gpsd~. Installed via ~apt~. This procedure was developed with
+ ~ntpsec~ version ~1.1.3~.
+
** Operating Procedures
*** Initial Startup
-**** Install Raspbian 10 (Buster) onto a Raspberry Pi Zero W.
-
-
-**** Install Hardware
+**** Perform initial setup.
+See [[file:../setup/README.org][Main Setup]] procedure.
+**** Install Hardware for time tracking
See [[https://ozzmaker.com/forums/topic/connecting-gps-pps-pin/][this]] Ozzmaker forum topic about connecting the BerryGPS-IMU
~T_PULSE~ pin to GPIO 18.
+#+CAPTION: An image showing how to connect the PPS signal from an Ozzmaker BerryGPS-IMU board to a Raspberry Pi Zero W.
+#+NAME: fig:PPS_BERRYGPS_RASPIZW
+[[../../img/Compact_Stratum_1_NTP_time_server_hardware,_October_2020.jpg]]
+
Connect the ~T_PULSE~ connection on the BerryGPS-IMU-3 to GPIO pin 18
(ex: with solder and wire) in order to provide the PPS data signal
generated by the BerryGPS-IMU to the Raspberry Pi. Processing of this
data signal is handled by adding a line to ~/boot/config.txt~ in the
next section ("Install Software").
-**** Install Software
-These instructions assume that ~gpsd~ has already been setup to
-provide NMEA sentences to ~gpspipe~ for location. See the ~README.org~
-in ~doc/location~ for details. Basically, ~gpsd~ needs to be told via
-its ~/etc/default/gpsd~ configuration file of which ~/dev/ttyS0~ will
-provide the raw GPS module data.
+Note: If it is desired to specify a custom GPIO pin besides the one
+recommended, see this [[https://raspberryautomation.com/connect-multiple-ds18b20-temperature-sensors-to-a-raspberry-pi/][Raspberry Autom]] article.
+
+**** Install Software for time tracking
+The time tracking function can be performed by two programs: ~gpsd~
+and ~ntpsec~.
+
+Basically, two things need to happen:
+
+1. ~gpsd~ needs to be pointed towards the correct device files for
+ incoming GPS data (in NMEA format) and the PPS signal ("pulse per
+ second"; a high precision time signal).
+
+2. ~ntpsec~ needs to be pointed towards the correct local IP addresses
+ where ~gpsd~ provides GPS data and the PPS signal.
+
+~gpsd~ then will provide GPS and PPS data to ~ntpsec~ via a "shared
+memory driver".
***** Install packages via ~apt~
Run the following command to install the required packages.
-: $ sudo apt install usbmount eject gpsd gpsd-clients python-gps pps-tools ntp
+: $ sudo apt install gpsd gpsd-clients python-gps pps-tools ntpsec
-***** Modify ~/boot/config.txt~
-In order to tell the Raspberry Pi to expect PPS data on ~BCM 18~ (pin
-number 12; see [[https://pinout.xyz/][RaspPi pinout]]), add the following line to
-~/boot/config.txt~ as described on [[https://ozzmaker.com/forums/topic/problems-with-pps-on-a-pi0w-running-raspian-and-attached-to-a-berrygps-imuv3/][this Ozzmaker page]]:
+***** Enable PPS device
+Modify the ~/boot/config.txt~ file in order to tell the Raspberry Pi
+to expect PPS data on ~BCM 18~ (pin number 12; see [[https://pinout.xyz/][link]]). This is done
+by adding the following line to ~/boot/config.txt~ as described on
+[[https://ozzmaker.com/forums/topic/problems-with-pps-on-a-pi0w-running-raspian-and-attached-to-a-berrygps-imuv3/][this Ozzmaker page]]:
: dtoverlay=pps-gpio,gpiopin=18
+The ~/boot/config.txt~ file can be modified via:
+
+: $ sudo nano /boot/config.txt
+
PPS data can be confirmed by running:
#+BEGIN_EXAMPLE
source 0 - assert 1595708077.003850580, sequence: 222 - clear 0.000000000, sequence: 0
#+END_EXAMPLE
-***** Add udev rule
-As per [[https://www.slsmk.com/how-to-setup-a-gps-pps-ntp-time-server-on-raspberry-pi/][the slsmk.com]] guide, create symbolic links expected by ~ntp~
-pointing to the PPS device. This may be performed by creating the file:
+Note: For older Raspberry Pi models, it may be necessary to enable
+~pps-gpio~ via modifications to ~/etc/modules~ (see [[https://www.raspberrypi.org/forums/viewtopic.php?p=757747#p757747][link]]).
+
+***** Enable GPS device
+The Ozzmaker BerryGPS-IMU makes NMEA sentences available via the
+serial "UART" device ~/dev/ttyAMA0~. If bluetooth has not been
+disabled, the Raspberry Pi OS automatically creates a software "UART"
+device at ~/dev/serial0~. See the "[[file:~/git-OC/ninfacyzga-01/doc/setup/README.org::*Disable%20Bluetooth][Disable Bluetooth]]" section in the
+[[file:../setup/README.org][Main Setup]] Initial Startup procedure for instructions on how to
+disable bluetooth to free up ~/dev/ttyAMA0~ for use by ~gpsd~.
+
+Note: Older ~ntp~ documentation indicates that ~ntp~ (and presumably
+~ntpsec~ might be able to access GPS data (ex: NMEA sentences) without
+the aid of ~gpsd~ itself if the data is available at a device named
+~/dev/ggp0~. Similarly, the same might apply to PPS data and the
+~/dev/gpspps0~ device. However, since the Raspberry Pi OS overlay
+system automatically creates ~/dev/pps0~ using the modifications to
+~/boot/config.txt~ (described [[*Enable PPS device][elsewhere]] in this procedure).
+
+***** Setup ~gpsd~
+See the "[[file:~/git-OC/ninfacyzga-01/doc/location/README.org::*Setup%20~gpsd~][Setup ~gpsd~]]" subsection within the "Initial Startup" section
+of the Location Logging [[file:~/git-OC/ninfacyzga-01/doc/location/README.org][~README.org~]] file. There is one additional
+change that must be made which is to add a ~/dev/pps0~ item to the
+~DEVICES=~ line in ~/etc/default/gpsd~ like so:
+
+: DEVICES="/dev/ttyAMA0 /dev/pps0"
+
+~/dev/ttyAMA0~ is where ~gpsd~ can get NMEA data from the GPS unit.
+
+~/dev/pps0~ is where ~gpsd~ can get a PPS signal.
+
+As an example, the following lines will be present in
+~/etc/default/gpsd~ if both location and time tracking are set up:
+
+#+BEGIN_EXAMPLE
+START_DAEMON="true"
+USBAUTO="false"
+DEVICES="/dev/ttyAMA0 /dev/pps0"
+GPSD_OPTIONS="-n"
+#+END_EXAMPLE
+
+***** Setup ~ntpsec~
+The ~ntpsec~ configuration file at ~/etc/ntpsec/ntp.conf~ must be
+modified to tell ~ntpsec~ how to retrieve and interpret the GPS and
+PPS data provided by ~gpsd~.
+
+In summary, lines need to be added telling ~ntpsec~ how often to poll
+certain sources (local or remote) for time information as well as how
+to prioritize and label information from each source.
+
+~ntpsec~ uses syntax simplified from that of ~ntp~. Specifically, it
+recommends use of the ~refclock~ keyword for configuring local
+hardware clocks such as GPS and PPS devices.
+
+Below is an example of lines that may be added to
+~/etc/ntpsec/ntp.conf~ in order to ensure that the system clock will always have
+
+#+BEGIN_EXAMPLE
+# Local time sources
+
+# Kernel PPS (precision seconds; driver 22)
+refclock pps unit 0 refid kPPS flag3 1 minpoll 4 maxpoll 4 stratum 1
+
+# GPS PPS reference (precision seconds; driver 28; root) (NTP1)
+refclock shm unit 1 refid PPS minpoll 4 maxpoll 4 iburst stratum 1
+
+# GPS Serial data reference (coarse time; driver28; root) (NTP0)
+refclock shm unit 0 refid GPS prefer time1 0.109 minpoll 4 maxpoll 4 iburst stratum 1
+
+# GPS PPS reference (precision seconds; driver 28; user) (NTP2)
+refclock shm unit 2 refid PPSuser minpoll 4 maxpoll 4 iburst stratum 1
+
+# Tolerate outliers (useful for coarse clocks)
+tos mindist 0.500
+#+END_EXAMPLE
+
+A complete working example of an ~ntp.conf~ file is found in Appendix
+A of this document.
+
+Commands useful for examining the shared memory driver used by ~gpsd~
+and ~ntpsec~ are:
+
+- ~sudo ntpshmmon~ : Shows live output of data using the shared memory
+ driver. ([[https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html][ref]])
+
+- ~sudo ipcs -m~ : Show live segments of the shared memory. ([[https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html][ref]])
+
+General references for this configuration file are:
+
+- "Raspberry Pi as a Stratum-1 NTP Server - Updating to the final NTP
+ configuration file" by David Taylor. [[http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html#ntp-conf][Link]]. Date: 2020-03-24. Note:
+ An example of kernel PPS transfer from ~gpsd~ to ~ntp~ via
+ ~127.127.22.0~.
+
+- "GPSD Time Service HOWTO" by Garry E. Miller. [[https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html][Link]]. Date:
+ 2020-06-28. Note: Explains how shared memory segments available at
+ ~127.127.28.0~, ~127.127.28.1~, ~127.127.28.2~, etc. work in context
+ of an ~ntp~ configuration file.
+
+- "Building a Stratum 1 NTP Server with a Raspberry Pi 4 and Adafruit
+ Ultimate GPS Hat". [[http://www.gregledet.net/computers/building-a-stratum-1-ntp-server-with-a-raspberry-pi-4-and-adafruit-ultimate-gps-hat/][Link]]. Date: 2020-02-23. Note: A concise example
+ between ~gpsd~ and ~ntp~ setup for a Raspberry Pi 4 using
+ ~127.127.28.0~ and ~127.127.28.1~. Recommends use of ~ntpsec~
+ instead of ~ntp~.
+
+Expalantions of some ~ntpsec~ [[https://docs.ntpsec.org/latest/comdex.html][commands and options]] used in the
+configuration file include:
+
+- ~refclock~ : An ~ntpsec~ keyword not present in ~ntp-4.2.8~ that is
+ meant to simplify configuration of reference clocks that use certain
+ [[https://docs.ntpsec.org/latest/refclock.html][drivers]] including ~pps~ ([[https://docs.ntpsec.org/latest/driver_pps.html][PPS Clock Discipline]]), ~shm~ ([[https://docs.ntpsec.org/latest/driver_shm.html][Shared Memory
+ Driver]]) . In ~ntp-4.2.8~ and earlier, in order to configure a clock,
+ instead of ~ntpsec~'s one keyword (~refclock~), two keywords would
+ be required (~server~ and ~fudge~).
+
+- ~server [address]~ : Tells ~ntpsec~ the address to query for time
+ information. May be IP address or URL. Additional options such as
+ ~minpoll~, ~maxpoll~, ~prefer~, and ~true~ may be added.
+
+- ~prefer~ : Indicates the source should be prioritized in some
+ way. How exactly the ~ntpsec~ mitigation rules (see [[https://docs.ntpsec.org/latest/prefer.html][ref]]) use the
+ ~prefer~ option is complicated but in the context of dealing with a
+ GPS source and a PPS source, the GPS source should have a ~prefer~
+ option. The PPS source may have a ~prefer~ option but it is not
+ necessary; adding ~prefer~ to a PPS source is useful in the corner
+ case that the GPS source is less reliable than another source (ex: a
+ remote clock specified by ~server~).
+
+- ~... shm ... flag1 1~ : For an ~shm~ driver, tells ~ntpsec~ to
+ ignore the default sanity check that discards any time that is more
+ than 4-hours off from the system clock. Note that ~ntpsec~ treats
+ ~shm flag1 1~ in the opposite manner as ~ntp~ (see [[https://docs.ntpsec.org/latest/driver_shm.html][ref]]).
+
+- ~... shm ... time1 [float]~ : Tells ~ntpsec~ that a latency
+ time of ~[float]~ seconds is required for data to travel from the
+ address to ~ntpsec~ (ex: a USB hub in the case of a GPS device that
+ connects via USB). (see [[https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html#_feeding_ntpd_from_gpsd][ref]]) This number of seconds should be
+ adjusted to reduce the `offset` time of the address indicated in the
+ output of the ~ntpq -pn~ command to near ~0.000~. Note that the
+ units of ~offset~ displayed by ~ntpq -pn~ are in milliseconds.
+
+- ~... refid [string]~ : Tells ~ntpsec~ a string used to label the source.
+
+- ~fudge~ : An ~ntp~ keyword that ~ntpsec~ developers do not recommend
+ using; ~ntpsec~ documentation for ~fudge~ is widthdrawn. For local
+ hardware providing GPS and PPS time information, ~fudge~ can mostly
+ be replaced with use of the ~refclock~ keyword instead.
+
+- ~fudge [address]~ : Tells ~ntpsec~ to consider additional options
+ when evaluating the accuracy of time from a given address.
+
+- ~fudge [address] ... flag3 1~ : An option that tells ~ntpsec~ to
+ enable "kernel PPS discipline" when interpreting the PPS signal at
+ the address. (see [[http://doc.ntp.org/4.2.8p7/drivers/driver22.html][ref]]).
+
+- ~stratum 1~ : Tells ~ntpsec~ to label the source as a "stratum 1"
+ time server. This means that it is a clock using NTP that is a
+ canonical (?) time source. For example, a stratum 0 NTP time server
+ would be an atomic clock. A stratum 1 NTP time server could be a
+ clock that uses a GPS receiver to synchronize to said atomic clock.
+
+- ~iburst~ : Tells ~ntpsec~ how often to query a source.
+
+- ~fudge [address] ... flag1 [float]~ : See description of ~... shm
+ ... time1 [float]~.
+
+- ~tos mindist [float]~ : Tells ~ntpsec~ to increase the tolerance for
+ outliers in the clock selection algorithm. Units of ~[float]~ are
+ seconds. The default value is ~0.001~ seconds. This [[http://doc.ntp.org/4.2.6/miscopt.html][reference]]
+ indicates that it is acceptable to raise this value for "clocks with
+ high jitter and a PPS signal". For the device being configured in
+ this guide, this is the case. ~ntpsec~ receives a kernel PPS signal
+ on ~127.127.22.0~ indicating when each second occurs but without
+ information about which second of the day is being ticked. ~ntpsec~
+ receives a coarse time from ~127.127.28.0~ supplied by ~gpsd~ that
+ is derived from the NMEA sentences generated by the GPS receiver;
+ this coarse time (high jitter) lacks the precision of the PPS signal
+ since NMEA sentence transmission times are not well-controlled.
+
+****** Disable DHCP services affecting ~ntpsec~
+Some processes that use [[https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol][DHCP]] (Dynamic Host Configuration Protocol) may
+cause configuration changes to configuration files of ~ntp~. Since
+~ntpsec~ is similar to ~ntp~, it is reasonable to take action to
+prevent this.
+
+Remove some files:
+
+: $ sudo rm /etc/dhcp/dhclient-exit-hooks.d/ntp
+: $ sudo rm /lib/dhcpcd/dhcpcd-hooks/50-ntp.conf
+
+In the "request" block of ~dhclient.conf~, remove ~dhcp6.sntp-servers~
+and ~ntp-servers~.
+
+: $ sudo nano /etc/dhcp/dhclient.conf
+
+For example, the following section of ~dhclient.conf~:
-: /etc/udev/rules.d/09-pps.rules
+#+BEGIN_EXAMPLE
+send host-name = gethostname();
+request subnet-mask, broadcast-address, time-offset, routers,
+ domain-name, domain-name-servers, domain-search, host-name,
+ dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
+ netbios-name-servers, netbios-scope, interface-mtu,
+ rfc3442-classless-static-routes, ntp-servers;
+#+END_EXAMPLE
-with the contents:
+should be changed to:
#+BEGIN_EXAMPLE
-KERNEL=="ttyAMA0", SUBSYSTEM=="tty", DRIVER=="", OWNER=="root", GROUP=="tty", MODE=="0777", SYMLINK+="gps0"
+send host-name = gethostname();
+request subnet-mask, broadcast-address, time-offset, routers,
+ domain-name, domain-name-servers, domain-search, host-name,
+ dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn,
+ netbios-name-servers, netbios-scope, interface-mtu,
+ rfc3442-classless-static-routes;
#+END_EXAMPLE
-***** Modify ~/etc/modules~
-For older versions of Raspberry Pi, it may be necessary to explicitly
-require the ~pps-gpio~ module to be loaded by making sure
-~/etc/modules~ contains the line:
+***** Disable CPU power saving
+Power saving featurs of the Raspberry Pi Zero W may also be disabled
+in order to improve accuracy.
+
+****** Configure CPU ~scaling_governor~
+If additional precision is required, the PPS signal may be made more
+reliable at the cost of increasing CPU power by configuring the CPU to
+always run at maximum frequency.[fn:se_20180320_raspicpugov] This
+change can be performed by modifying the following file as root:
+
+: /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
+
+The file should consist of one line. Change
-: pps-gpio
+: ondemand
-According to [[https://www.raspberrypi.org/forums/viewtopic.php?p=757747#p757747][this]] post on 2015-05-13T09:14 by [[https://www.raspberrypi.org/forums/memberlist.php?mode=viewprofile&u=31454][ame]] on the Raspberry Pi
-forums,
+to
-#+BEGIN_QUOTE
-rowlandski wrote:
-> Hi,
->
-> I want the RPi to load/probe the w1-gpio module on boot.
->
-> I have added:
->
-> sudo modprobe w1-gpio
->
-> To the etc/modules file, but on boot it is not loaded.
-> I have checked this by the lsmod command. If i then enter the above line manually and then check it's there loaded.
->
-> What's wrong with my line on code in the modules file?
->
-> Thanks
+: performance
-You no longer need to load modules for some devices. It's handled by devicetree.
+.
-Search for "devicetree" on the forum, or start here:
-https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=97314
-#+END_QUOTE
+This change can be performed via the ~nano~ text editor by running the
+following commands:
-As of 2020-07-25, using Raspbian Buster 10 with a BerryGPS-IMU v3,
-~/etc/modules~ did not need to be modified.
+: $ sudo su -
+: # nano /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
-***** Remove DHCP client hooks
-As per [[https://www.slsmk.com/how-to-setup-a-gps-pps-ntp-time-server-on-raspberry-pi/][this]] guide, "remove ntp DHCP hook (so that it doesn't override ntp settings)".
+Additionally, in order to prevent the ~raspi-config~ init script from
+reverting this text file back to ~ondemand~ after a reboot, this
+script must be disabled via:
-This can be performed by running the following command (shown in
-script form for readability):
+: $ sudo systemctl disable raspi-config
+
+****** Configure ~/boot/config.txt~
+Modify ~/boot/config.txt~ so that it contains these lines in order to
+disable power saving functions:
#+BEGIN_EXAMPLE
-if [ -f "/etc/dhcp/dhclient-exit-hooks.d/ntp" ]; then
- mv /etc/dhcp/dhclient-exit-hooks.d/ntp /etc/dhcp/dhclient-exit-hooks.d/xxxntp-orig;
-else
- echo "NTP exit hook does not exist";
-fi;
+# Disable power saving
+nohz=off
#+END_EXAMPLE
+[fn:se_20180320_raspicpugov] Title:[[https://raspberrypi.stackexchange.com/questions/9034/how-to-change-the-default-governor]["How to change the default governor?"]]; Author:[[https://raspberrypi.stackexchange.com/users/5538/goldilocks][goldilocks]]; Date: 2018-03-20; Website:stackexchange.com;
+
*** Normal Startup
*** Normal Operation
*** Normal Shutdown
*** Unscheduled Shutdown
+** Appendix A
+*** Example ~ntp.conf~ for ~ntpsec~
+Below is an example ~ntp.conf~ file for use with ~ntpsec~.
+
+#+BEGIN_EXAMPLE
+# /etc/ntpsec/ntp.conf, configuration for ntpd; see ntp.conf(5) for help
+
+# Drift file
+driftfile /var/lib/ntpsec/ntp.drift
+
+# Leap seconds definition provided by tzdata
+leapfile /usr/share/zoneinfo/leap-seconds.list
+
+# Log file
+#logfile /var/log/ntp.log
+
+
+# You must create /var/log/ntpsec (owned by ntpsec:ntpsec) to enable logging.
+#statsdir /var/log/ntpsec/
+#statistics loopstats peerstats clockstats
+#filegen loopstats file loopstats type day enable
+#filegen peerstats file peerstats type day enable
+#filegen clockstats file clockstats type day enable
+
+
+# Comment this out if you have a refclock and want it to be able to discipline
+# the clock by itself (e.g. if the system is not connected to the network).
+#tos minclock 4 minsane 3
+
+
+# Local time sources
+
+# Kernel PPS (precision seconds; driver 22)
+refclock pps unit 0 refid kPPS flag3 1 minpoll 4 maxpoll 4 stratum 1
+
+# GPS PPS reference (precision seconds; driver 28; root) (NTP1)
+refclock shm unit 1 refid PPS minpoll 4 maxpoll 4 iburst stratum 1
+
+# GPS Serial data reference (coarse time; driver28; root) (NTP0)
+refclock shm unit 0 refid GPS prefer time1 0.109 minpoll 4 maxpoll 4 iburst stratum 1
+
+# GPS PPS reference (precision seconds; driver 28; user) (NTP2)
+refclock shm unit 2 refid PPSuser minpoll 4 maxpoll 4 iburst stratum 1
+
+# Tolerate outliers (useful for coarse clocks)
+tos mindist 0.500
+
+
+# Specify one or more NTP servers.
+
+# 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: <https://www.pool.ntp.org/join.html>
+server time.nist.gov iburst
+server tick.usno.navy.mil iburst
+server 0.us.pool.ntp.org iburst
+#server 0.us.pool.ntp.org iburst
+#server 0.us.pool.ntp.org iburst
+#server 0.us.pool.ntp.org iburst
+pool 0.debian.pool.ntp.org iburst
+#pool 1.debian.pool.ntp.org iburst
+#pool 2.debian.pool.ntp.org iburst
+#pool 3.debian.pool.ntp.org iburst
+
+
+# Access control configuration; see /usr/share/doc/ntpsec-doc/html/accopt.html
+# for details.
+#
+# Note that "restrict" applies to both servers and clients, so a configuration
+# that might be intended to block requests from certain clients could also end
+# up blocking replies from your own upstream servers.
+
+# By default, exchange time with everybody, but don't allow configuration.
+restrict default kod nomodify nopeer noquery limited
+
+# Local users may interrogate the ntp server more closely.
+restrict 127.0.0.1
+restrict ::1
+#+END_EXAMPLE
+
+* Discard
+
+** Transitional ntp to ntpsec config file snippet
+# Kernel PPS (precision seconds; driver 22)
+#server 127.127.22.0 minpoll 4 maxpoll 4 true
+#fudge 127.127.22.0 flag3 1 refid kPPS stratum 1
+refclock pps unit 0 refid kPPS flag3 1 minpoll 4 maxpoll 4 stratum 1
+
+# GPS PPS reference (precision seconds; driver 28; root) (NTP1)
+#server 127.127.28.1 minpoll 4 maxpoll 4 iburst
+#fudge 127.127.28.1 flag1 1 refid PPS
+refclock shm unit 1 refid PPS minpoll 4 maxpoll 4 iburst stratum 1
+
+# GPS Serial data reference (coarse time; driver28; root) (NTP0)
+#server 127.127.28.0 minpoll 4 maxpoll 4 iburst prefer
+#fudge 127.127.28.0 flag1 1 time1 0.109 refid GPS stratum 1
+refclock shm unit 0 refid GPS prefer time1 0.109 minpoll 4 maxpoll 4 iburst stratum 1
+# GPS PPS reference (precision seconds; driver 28; user) (NTP2)
+#server 127.127.28.2 minpoll 4 maxpoll 4 iburst
+#fudge 127.127.28.2 flag1 1 refid PPSuser stratum 1
+refclock shm unit 2 refid PPSuser minpoll 4 maxpoll 4 iburst stratum 1
+# Tolerate outliers (useful for coarse clocks)
+tos mindist 0.500
projects / EVA-2020-02.git / commitdiff
