ROS (Robot Operating System) is a widely used open-source robotics middleware. It is a collection of software libraries and tools that help developers build complex robotics applications. ROS uses a distributed architecture, and the two main components of this architecture are nodes and topics.
Also Read: creating ROS packages
In this blog post, we will explain ROS nodes and topics in an easy-to-understand manner.
ROS Nodes
A node is a fundamental unit of computation in ROS. It is a process that performs a specific task and communicates with other nodes through ROS messages. A node can publish messages, subscribe to messages, or provide a service to other nodes.
Nodes can be written in different programming languages, including C++, Python, and Java. A node can also be a simple script or a complex program.
ROS Topics
A topic is a named bus over which nodes exchange messages. A topic is like a radio station, where the broadcaster sends a message, and multiple listeners can receive it.
ROS topics enable communication between nodes. When a node publishes a message on a topic, all nodes that are subscribed to that topic receive the message. A node can subscribe to multiple topics, and a topic can have multiple publishers and subscribers.
ROS topics can be of different types, including standard ROS messages like string, float, and integer, or custom messages that you define in your application.
Example
Let's consider a simple example to illustrate how nodes and topics work in ROS. Suppose you have two nodes: one node controls the movement of a robot, and the other node controls a camera mounted on the robot.
The movement node publishes messages on a topic called "robot_movement," which contains the robot's velocity and direction. The camera node subscribes to the "robot_movement" topic and adjusts the camera angle based on the robot's movement.
In this example, the movement node and the camera node communicate through the "robot_movement" topic, which enables them to work together to accomplish a specific task.
Conclusion
ROS nodes and topics are the core components of the ROS distributed architecture. Nodes perform specific tasks, and topics enable communication between nodes. Understanding nodes and topics are essential for developing complex robotics applications in ROS. We hope this blog post has provided you with an easy-to-understand explanation of ROS nodes and topics. In the next blog post, let's create a publisher and subscriber in ROS using python.