NTP

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Revision as of 15:06, 29 March 2017 by JulienB (Talk | contribs) (Debian install)

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From https://en.wikipedia.org/wiki/Network_Time_Protocol, "Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks." Practically, it allows you to have current time/date on your APF even if your don't have an RTC (you will need an Internet connection or a GPS ;-)).

Get current Time from Internet

# ntpd -nqp 217.147.208.1

Time synchronisation from GPS

Buildroot Debian
  • You will need the "real" NTP daemon, not the Busybox one.
root@opos6ul:~# apt-get install ntp
  • Edit config file (/etc/ntp.conf):
# Allow only time queries, at a limited rate, sending KoD when in excess.
# Allow all local queries (IPv4, IPv6)
restrict default nomodify nopeer noquery limited kod
restrict 127.0.0.1
restrict [::1]

server 127.127.20.0 mode 17 minpoll 4 maxpoll 4 prefer
fudge 127.127.20.0 flag3 1 flag2 0 flag1 1 time1 0.0

  • 127.127.20.0 means: "use /dev/gps0 and parse it as NMEA to get time" (See [1]).
  • mode 17 is for 9600 bauds GPS providing GPRMC frames
  • To create /dev/gpsX (here GPS is connected to UART2):
# ln -sf /dev/ttymxc1 /dev/gps0
  • To launch ntpd:
# /usr/sbin/ntpd -g -c /etc/ntp.conf

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