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

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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 page:

1. https://docs.ros.org/en/humble/Tutorials/Intermediate/Launch/Creating-Launch-Files.html

ROS launch files are files that can be used to deploy a set of nodes and topics; this allows for a docker-compose like launch. That enables developers to launch and configure multiple nodes at the same time. These files can come in different formats:

1. Python
2. XML
3. YAML

Examples

Simple launch file with parameter loading

<launch>
  <node pkg="turtlesim" exec="turtlesim_node" name="sim" namespace="turtlesim1"/>
  <node pkg="turtlesim" exec="turtlesim_node" name="sim" namespace="turtlesim2"/>
  <node pkg="turtlesim" exec="mimic" name="mimic">
    <remap from="/input/pose" to="/turtlesim1/turtle1/pose"/>
    <remap from="/output/cmd_vel" to="/turtlesim2/turtle1/cmd_vel"/>
  </node>
</launch>

This file is made from a number of node values; these nodes reference a package and a specific node from it. Also, with it you can also control the namespace value to allow multiple nodes with the same base topic name, as discussed before in the topics section. You also can control and modify the subscription topics with the remap key.