ntpd_driver

This ROS node listen sensor_msgs/TimeReference and send it to ntpd via SHM (like gpsd).

Parameter ~/shm_unit define SHM unit (in ntp.conf) (int, default: 2). Parameter ~/time_ref_topic define the topic to subscribe to (string, default: "~/time_ref"). Parameter ~/fixup_date enable/disable date fixup (bool, default: false)

System configuration

ntpd configuration

Add this to /etc/ntp.conf:

### GPS SHM driver
server 127.127.28.2 minpoll 4 maxpoll 4
fudge 127.127.28.2 time1 0.5 stratum 12 refid ROS

And then restart ntp service.

Run example:

rosrun ntpd_driver shm_driver _shm_unit:=2 _time_ref_topic:=/mavros/time_reference

chrony configuration

Add this to /etc/chrony/chrony.conf:

### SHM driver
refclock SHM 0 delay 0.5 refid ROS

And then restart chrony service.

Run example:

rosrun ntpd_driver shm_driver _shm_unit:=0 _time_ref_topic:=/mavros/time_reference

Date fixup configuration (sudo)

On my Raspberry Pi 2 ntpd reject SHM data if system date is not set (e.g. JAN 1970). To fix that shm_driver now can set system time if it unset.

For setting date program requires root privileges, so used sudo.

Add this to /etc/sudoers (using visudo):

%sudo	ALL=NOPASSWD: /bin/date

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