Getting Started with ROS on Embedded Systems - User Guide - C++ - Initialization

Getting Started with ROS on Embedded Systems
ROS on Embedded Systems Basics
Getting Started
Installation Configuration Setting up environment Execution
C++ User Guide
Package set up Initialization Topics Messages Names Publishers and subscribers Launch files Parameters
Examples
Basic pipelines V4L2 capture node Turn detector node Proximity detector node
Performance
Xavier TX1 TX2 Nano
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Introduction

This wiki is based on the following ROS page: http://wiki.ros.org/roscpp/Overview/Initialization%20and%20Shutdown

There are two levels of initialization for a roscpp Node:

1. Initializing the node through a call to one of the ros::init() functions. This provides command line arguments to ROS, and allows you to name your node and specify other options.
2. Starting the node is most often done through creation of a ros::NodeHandle, but in advanced cases can be done in different ways.

Initialization

And example of initialization for the a ROS node inside a main.cpp can be the following:

ros::init(argc, argv, "rr_node");

Starting

Calling init doesn't actually start the node, it just initialized it, in order to start it, you can create a node handle, this will call the ros::start underneath:

ros::NodeHandle node_handle("node_namespace");

Look here that we just assigned a node namespace, we will take about them later in the names section.

Testing

You can test the node by adding this to the code:

while (ros::ok()){
    /* Do something here */
    ros::spin();
}

After compilation, you can launch the node by using:

rosrun <package> <node_name_executable>