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)
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
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
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