rtt_ros2_params - ROS parameter support

Description

ROS2 provides a slightly different infrastructure to deal with parameters compared to ROS 1. An introduction guide can be found in Understanding ROS2 parameters. The main difference is that there is no longer a centralized parameter server, but instead, parameters are maintained per node.

rosparam service

This package provides a new Orocos service called rosparam that can be loaded globally and per Orocos component. The service provides 4 operations:

• getParameter(): loads a parameter from the ROS2 node parameter facility and returns its value.
• loadProperty(): loads a parameter from the ROS2 node parameter facility into an Orocos property.
• setParameter(): sets a parameter into the ROS2 node parameter facility. With the default rtt_ros2_node::Node, if the parameter does not exist, rosnode declares one.
• storeProperty(): sets a parameter into the ROS2 node parameter facility from the value of an Orocos property. With the default rtt_ros2_node::Node, if the parameter does not exist, rosnode declares one.

Scripting Interface

This package can be imported with:

import("rtt_ros2_params")

Then, the service can be loaded into a component named <component> with:

<component>.loadService('rosparam')

<component> will have a new service named rosparam that provides the operations described. These operations can be called with:

<component>.rosparam.setParameter( <args> )
<component>.rosparam.getParameter( <args> )
<component>.rosparam.loadProperty( <args> )
<component>.rosparam.storeProperty( <args> )

Requirements

In order to work, this service requires two other elements being loaded before calling the operations.

• A ROS2 node service must exist for the component where this service is loaded or globally.
• The typekits provided in rtt_ros2_rclcpp_typekit and its dependencies must be loaded

These prerequirements can be achieved by:

import("rtt_ros2")
ros.import("rtt_ros2_params")

To load a ROS2 node specific for a component, please, read the related documentation.