1.5.3 Use Turtlesim

Open a new terminal and source ROS 2 again.

Now you will run a new node to control the turtle in the first node:

ros2 run turtlesim turtle_teleop_key

At this point you should have three windows open: a terminal running turtlesim_node, a terminal running turtle_teleop_key and the turtlesim window. Arrange these windows so that you can see the turtlesim window, but also have the terminal running turtle_teleop_key active so that you can control the turtle in turtlesim.

Use the arrow keys on your keyboard to control the turtle. It will move around the screen, using its attached “pen” to draw the path it followed so far.

Pressing an arrow key will only cause the turtle to move a short distance and then stop. This is because, realistically, you wouldn’t want a robot to continue carrying on an instruction if, for example, the operator lost the connection to the robot.

You can see the nodes, and their associated topics, services, and actions, using the list subcommands of the respective commands:

ros2 node list
ros2 topic list
ros2 service list
ros2 action list

You will learn more about these concepts in the coming tutorials. Since the goal of this tutorial is only to get a general overview of turtlesim, you will use rqt to call some of the turtlesim services and interact with turtlesim_node.