1.2 First ROS2 node

1.2 First ROS2 node#

To get your first node running, it helps to shutdown all the nodes that are started by default on the MIRTE robot. This can be done by typing in the terminal:

$ sudo systemctl stop mirte-ros

This will shutdown all MIRTE-related ROS nodes.

As you’ve seen in the presentation, one of the core elements of ROS2 are nodes. These are just small executables that connect with the ROS2 API. In this tutorial you will learn how to create your first ROS node. In VSCode you can open a new file and save the following code as my_node.py:

import rclpy
from rclpy.node import Node

def main():
  rclpy.init()
  my_node = Node('hello_world_node')
  my_node.get_logger().info("Hello world")
  try:
     rclpy.spin(my_node)
  except KeyboardInterrupt:
     return

if __name__ == '__main__':
  main()

You can now run this program by typing the following in the terminal:

$ python3 my_node.py

You should see the string ‘Hello world’ being printed on the screen once. If you did it correctly the node is still spinning, so the terminal is still busy. You can check that the node is indeed running by opening another terminal ():

/hello_world_node

$ ros2 node list

This should give you the name of the node (‘hello_world_node’) as set in line 6. Congratulations, you have your first ROS2 node running. But this is not the best way of doing this.