ros-chrony

ROS package that interfaces the time synchronization chrony daemon and provide status of synchronization on ROS topics.

GPSD and Chrony Synchronization

Installation of GPSD

1. Download the lastest version of GPS here -> choose at least v3.22 because lower versions can give you bugs according to official doc.
2. untar the file with tar -xzf gpsd-XX.Y.tar.gz
3. go to the gpsd directory with cd gpsd-XX.Y
4. go in root mode with sudo su to avoid any permissions problems
5. do scons && scons check && scons udev-install (you may need to install scons before sudo apt install scons)
6. This should work and you can start the daemon with gpsd to see if it is installed successfully.
7. Official tutorial here if you got any problems.

Installation of Chrony

1. Download lastest release of chrony here
2. Extract the file.
3. Go to the directory cd chrony-X.Y
4. To avoid any permissions problems go in root mode sudo su
5. Do ./configure and wait until the end.
6. Once step 6 is done, do make to build programs
7. After step 6 do make docs to have HTML docs.
8. make install to install compiled programs of step 6.
9. make install-docs to install docs.
10. You should be able to run chronyd in a terminal.

Configuring GPSD and Chrony

GPSD

For GPSD you can have a port listening problem, you maybe have to create a file in /etc/systemd/system/gpsd.socket.d/ -> create a file named socket.conf

configure with this :

[Socket] 
#First blank ListenStream clears the system defaults
ListenStream=
ListenStream=2947
ListenStream=/var/run/gpsd.sock

Chrony

To synchronize GPS with chrony we need to modify this file nano /etc/chrony/chrony.conf. In this file we have to add those lines at the end : refclock SOCK /var/run/chrony.ttyS0.sock delay 0.0 refid GPS refclock SHM 1 offset 0.0 delay 0.0 refid PPS

ttyS0 was our serial port you may be have to change that.

You can try to follow this tutorial here this is official GPSD documentation, but the refclock SOCK /run/chrony.ppsX.sock didn't work for us.

After this you can start both daemons with

sudo chronyd -f /etc/chrony/chrony.conf sudo gpsd -n /dev/ttyS0 -> S0 is 1st serial port, you may need to change.

To check if it's working do : chronyc sources -v (-v is useful to understand symbols)

You should have something like : #- GPS or #+ GPS and under #* PPS If you have those sign, sources are synchronized.

Authors and acknowledgment

Corentin Boulongne & Gérald Dherbomez

License

MIT License