#THE CLOCKER CODE#

This can be done in a launchfile or from the command line. In order for a ROS node to use simulation time according to the /clock topic, the /use_sim_time parameter must be set to true before the node is initialized. Using Simulation Time from the /clock Topic NOTE: this is not an API for real-time systems! If you do not synchronize the wall-clocks of multiple machines, they will not agree on temporal calculations like those used in tf. ntp, our recommended syncronization tool is chrony) for doing this. ROS does not provide this functionality as there are already well-established methods (e.g. When using wall-clock time on multiple machines, it is important that you synchronize time between them. These APIs are described briefly below, though you should familiarize yourself with your client library of choice for more details. This will allow your system to have a consistent time measurement whether it is using the wall-clock or a simulated clock.

#THE CLOCKER CODE#

In order for your code to take advantage of the ROS simulation time, it is important that all code use the appropriate ROS client library Time API for accessing time and sleeping instead of using the language-native routines. To support this, the ROS client libraries can listen to the /clock topic that is used to publish 'simulation time'. For example, if you are playing back sensor data into your system, you may wish to have your time correspond to the timestamps of the sensor data. When you are running a simulation or playing back logged data, however, it is often desirable to instead have the system use a simulated clock so that you can have accelerated, slowed, or stepped control over your system's perceived time. Normally, the ROS client libraries will use your computer's system clock as a time source, also known as the 'wall-clock' or 'wall-time' (like the clock on the wall of your lab). Using Simulation Time from the /clock Topic.

The clocker