Parameters

Each node has parameters. Parameters are ways for external processes or people to tweak the node. In MC-ONE, parameters are typically managed by the robot engineer using the Monitor.

Parameters can be accessed in various ways:

• through the command line, using ros2 param ...
• by passing them to the node executable as --ros-args
• using RQt
• using the Monitor

Command-line Interface

Access to parameters via the command-line interface works as follows:

• List All Parameters: ros2 param list
• List All Parameter of a Node: ros2 param list <node>
• Describe a Parameter: ros2 param describe <node> <parameter>
• Get a Parameter Value: ros2 param get <node> <parameter>
• Set a Parameter Value: ros2 param set <node> <parameter> <value>
• Dump All Parameters of a Node: ros2 param dump <node>

A detailed description of the command-line interface can be found at https://docs.ros.org/en/jazzy/How-To-Guides/Using-ros2-param.html.

Note: With the MC-ONE Stack it's not possible to create or delete parameters on the fly.

Passing Parameters via --ros-args

When starting a node, you can pass parameters using the command-line interface:

ros2 run <package> <node> --ros-args -p <parameter>:=<value>

Or load a YAML-file with several parameters:

ros2 run <package> <node> --ros-args --params-file <file>.yaml

Note that system persistence via the Monitor overwrites parameter values specified by using --ros-args or --params-file.

A more detailed description can be found at https://docs.ros.org/en/jazzy/How-To-Guides/Node-arguments.html.

Using RQt

RQt is a UI framework with a bunch of plugins to view and edit almost anything in a running ROS2 system. One of the components is a parameter editor you can use to interact with the parameters of a node.

A more detailed description can be found at https://wiki.ros.org/rqt.

Using the Monitor

All parameters in the system are presented on the Monitor parameter page as well. They can be edited there, and are persistent.