# Raspberry Pi + GPS ModuleでStratum1なNTPサーバをつくる ## 配線 - あとでかくぞ． ## 大切なこと - raspberry piのserial consoleをdisableすること． - serialがttyAMA0に割り当てられること - gpsmon/cgpsを利用してppsのoffsetを掌握し，/etc/chrony/chrony.confのoffsetを調整すること． - これをやらないと処理遅延によるoffsetがかかってしまって絶対時間が合わない． - いくらgpsのppsを利用しているとはいえ，offsetは避けられない．設定しない場合でもあるoffsetをもつjitter/err marginの少ないNTPとしては成立すると思う． - `refclock SHM 1 lock NMEA refid PPS precision 1e-9 offset 0.100500` ## procedure ``` jp7fkf@lab1:~ $ uname -a Linux rasp03r.live 4.19.97+ #1294 Thu Jan 30 13:10:54 GMT 2020 armv6l GNU/Linux jp7fkf@lab1:~ $ sudo systemctl stop serial-getty@ttyAMA0.service jp7fkf@lab1:~ $ sudo systemctl disable serial-getty@ttyAMA0.service jp7fkf@lab1:~ $ sudo apt install gpsd gpsd-clients pps-tools jp7fkf@lab1:~ $ jp7fkf@lab1:~ $ jp7fkf@lab1:~ $ sudo timedatectl status Local time: Fri 2020-02-28 19:14:50 JST Universal time: Fri 2020-02-28 10:14:50 UTC RTC time: n/a Time zone: Asia/Tokyo (JST, +0900) System clock synchronized: yes NTP service: active RTC in local TZ: no jp7fkf@lab1:~ $ jp7fkf@lab1:~ $ cat /boot/cmdline.txt console=tty1 root=PARTUUID=738a4d67-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait jp7fkf@lab1:~ $ cat /boot/config.txt # For more options and information see # http://rpf.io/configtxt # Some settings may impact device functionality. See link above for details # uncomment if you get no picture on HDMI for a default "safe" mode #hdmi_safe=1 # uncomment this if your display has a black border of unused pixels visible # and your display can output without overscan #disable_overscan=1 # uncomment the following to adjust overscan. Use positive numbers if console # goes off screen, and negative if there is too much border #overscan_left=16 #overscan_right=16 #overscan_top=16 #overscan_bottom=16 # uncomment to force a console size. By default it will be display's size minus # overscan. #framebuffer_width=1280 #framebuffer_height=720 # uncomment if hdmi display is not detected and composite is being output #hdmi_force_hotplug=1 # uncomment to force a specific HDMI mode (this will force VGA) #hdmi_group=1 #hdmi_mode=1 # uncomment to force a HDMI mode rather than DVI. This can make audio work in # DMT (computer monitor) modes #hdmi_drive=2 # uncomment to increase signal to HDMI, if you have interference, blanking, or # no display #config_hdmi_boost=4 # uncomment for composite PAL #sdtv_mode=2 #uncomment to overclock the arm. 700 MHz is the default. #arm_freq=800 # Uncomment some or all of these to enable the optional hardware interfaces #dtparam=i2c_arm=on #dtparam=i2s=on #dtparam=spi=on # Uncomment this to enable infrared communication. #dtoverlay=gpio-ir,gpio_pin=17 #dtoverlay=gpio-ir-tx,gpio_pin=18 # Additional overlays and parameters are documented /boot/overlays/README # Enable audio (loads snd_bcm2835) dtparam=audio=on [pi4] # Enable DRM VC4 V3D driver on top of the dispmanx display stack dtoverlay=vc4-fkms-v3d max_framebuffers=2 [all] #dtoverlay=vc4-fkms-v3d enable_uart=1 core_freq=250 #added! dtoverlay=pps-gpio,gpiopin=18 #added! jp7fkf@lab1:~ $ cat /etc/modules # /etc/modules: kernel modules to load at boot time. # # This file contains the names of kernel modules that should be loaded # at boot time, one per line. Lines beginning with "#" are ignored. pps-gpio/etc/default/gpsd jp7fkf@lab1:~ $ cat # Default settings for the gpsd init script and the hotplug wrapper. # Start the gpsd daemon automatically at boot time START_DAEMON="true" # Use USB hotplugging to add new USB devices automatically to the daemon USBAUTO="true" # Devices gpsd should collect to at boot time. # They need to be read/writeable, either by user gpsd or the group dialout. DEVICES="/dev/ttyAMA0 /dev/pps0" # Other options you want to pass to gpsd GPSD_OPTIONS="-n" jp7fkf@lab1:~ $ cgps -s jp7fkf@lab1:~ $ gpsmon jp7fkf@lab1:~ $ sudo systemctl disable systemd-timesyncd Removed /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service. Removed /etc/systemd/system/dbus-org.freedesktop.timesync1.service. jp7fkf@lab1:~ $ sudo systemctl stop systemd-timesyncd jp7fkf@lab1:~ $ jp7fkf@lab1:~ $ sudo apt install chrony # Welcome to the chrony configuration file. See chrony.conf(5) for more # information about usuable directives. # pool 2.debian.pool.ntp.org iburst pool ntp.nict.jp maxsources 4 noselect pool ntp.jst.mfeed.ad.jp maxsources 4 noselect # NEMA by GPS refclock SHM 0 refid NMEA precision 1e-1 noselect refclock SHM 1 lock NMEA refid PPS precision 1e-9 offset 0.100500 # This directive specify the location of the file containing ID/key pairs for # NTP authentication. keyfile /etc/chrony/chrony.keys # This directive specify the file into which chronyd will store the rate # information. driftfile /var/lib/chrony/chrony.drift # Uncomment the following line to turn logging on. #log tracking measurements statistics # Log files location. logdir /var/log/chrony # Stop bad estimates upsetting machine clock. maxupdateskew 100.0 # This directive enables kernel synchronisation (every 11 minutes) of the # real-time clock. Note that it can’t be used along with the 'rtcfile' directive. rtcsync # Step the system clock instead of slewing it if the adjustment is larger than # one second, but only in the first three clock updates. makestep 1 3 # Allow NTP client access from local network. allow 10.1.0.0/24 allow 10.2.0.0/24 jp7fkf@lab1:~ $ chronyc sources -v 210 Number of sources = 2 .-- Source mode '^' = server, '=' = peer, '#' = local clock. / .- Source state '*' = current synced, '+' = combined , '-' = not combined, | / '?' = unreachable, 'x' = time may be in error, '~' = time too variable. || .- xxxx [ yyyy ] +/- zzzz || Reachability register (octal) -. | xxxx = adjusted offset, || Log2(Polling interval) --. | | yyyy = measured offset, || \ | | zzzz = estimated error. || | | \ MS Name/IP address Stratum Poll Reach LastRx Last sample =============================================================================== #? NMEA 0 4 377 23 +301ms[ +301ms] +/- 100ms #* PPS 0 4 377 21 +1232ns[+1929ns] +/- 1000ns ``` ## memo - `ppstest /dev/pps0` ## References - [GPSD Time Service HOWTO](https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html) - [Raspberry Pi 3 Model B + USB接続GPSレシーバ + ChronyでStratum 1なNTPサーバを作る – Lunatilia](https://lunatilia.wordpress.com/2019/01/29/building_stratum-1_ntp-server_with_raspi3_and_bu-353s4_and_chrony/) - [GPSモジュールを接続したRaspberry piでchronyを動作 - Qiita](https://qiita.com/RCA3610/items/0b3671cd272e430083d1) - [Raspberry pi3とGPSモジュールを接続してNTPサーバを構築 - Qiita](https://qiita.com/RCA3610/items/c478bb087acdad418cd3) - [GPS電波をRaspberry Piで読み取り、時間と位置把握する](https://www.rs-online.com/designspark/add-gps-time-and-location-to-a-raspberry-pi-project-jp) - [AE-GNSS_manual_r1.00s.pdf](http://akizukidenshi.com/download/ds/akizuki/AE-GNSS_manual_r1.00s.pdf) - [17.3. chrony の使用 Red Hat Enterprise Linux 7 | Red Hat Customer Portal](https://access.redhat.com/documentation/ja-jp/red_hat_enterprise_linux/7/html/system_administrators_guide/sect-using_chrony)