doc/time/README.org

   1 * Time
   2 This document was created by Steven Baltakatei Sandoval on
   3 ~2020-07-23T22:27Z~ under a [[https://creativecommons.org/licenses/by-sa/4.0/][Creative Commons BY-SA 4.0 license]]. It
   4 was updated by Steven Baltakatei Sandoval on ~2020-07-25T19:34Z~
   5 ** Development Task list
   6 *** Set up prototype unit
   7 **** Solder wire for PPS signal
   8 **** Follow guide
   9 - [[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.
  10 - [[http://www.satsignal.eu/raspberry-pi/Schmidt-RPZ-NTP-2016.pdf][Schmidt article]] on Raspberry Pi Zero time server.
  11 - [[https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html][GPSD dev ref]] page for ~gpsd~ interfacing with ~ntp~.
  12 *** Document prototype unit
  13 ** Narrative
  14 The ~ninfacyzga-01~ device is equipped with an Ozzmaker BerryGPS-IMU
  15 module which provides time and location data to ~gpsd~. The time is
  16 provided by GPS satellites which themselves are [[https://science.nasa.gov/science-news/science-at-nasa/2002/08apr_atomicclock/][equipped]] with atomic
  17 clocks. This extremely accurate set of clocks are needed since a GPS
  18 receiver calculates its position in space using a General Relativity
  19 calculation that uses the small variations in the time stamps received
  20 from each satellite. This means that ~gpsd~ may be used to set the
  21 system clock without a need for an internet connection to a default
  22 Debian time server; ~ninfacyzga-01~ can be its own time server.
  23 ** Description
  24 *** Hardware
  25 Ozzmaker BerryGPS-IMU, Version 3
  26 *** Software
  27 This guide describes steps that may be used to convert a Raspberry Pi
  28 into a time server using ~gpsd~.
  29 ** Operating Procedures
  30 *** Initial Startup
  31 **** Install Raspbian 10 (Buster) onto a Raspberry Pi Zero W.
  32 **** Install Hardware
  33 See [[https://ozzmaker.com/forums/topic/connecting-gps-pps-pin/][this]] Ozzmaker forum topic about connecting the BerryGPS-IMU
  34 ~T_PULSE~ pin to GPIO 18.
  35
  36 Connect the ~T_PULSE~ connection on the BerryGPS-IMU-3 to GPIO pin 18
  37 in order to enable ~gpsd~ to read the PPS signal for forwarding to
  38 ~ntp~.
  39
  40 **** Install Software
  41 Run the following command to install the required packages.
  42 : $ sudo apt install usbmount eject gpsd gpsd-clients python-gps pps-tools ntp
  43
  44 These instructions assume that ~gpsd~ has already been setup to
  45 provide NMEA sentences to ~gpspipe~ for location. See the ~README.org~
  46 in ~doc/location~ for details. Basically, ~gpsd~ needs to be told via
  47 its ~/etc/default/gpsd~ configuration file of which ~/dev/tty???~ will
  48 provide the raw GPS module data.
  49
  50 *** Normal Startup
  51 *** Normal Operation
  52 *** Normal Shutdown
  53 *** Unscheduled Shutdown
  54
  55