Why do I get the error message 'Could not retrieve the system state of the ROS master' when I try to set up ROS Subscribers in MATLAB R2022a?

I'm using the ROS Toolbox to connect MATLAB R2022a with Gazebo. I'm able to initialize my connection to the ROS master without any error. However, I encounter getting the following error message when I try to set up ROS Subscribers:

'Could not retrieve the system state of the ROS master'

How can I resolve this error?

Answer 1

[MathWorks Support Team]

This error appears because you are trying to subscribe to a topic that the ROS master does not have. Execute the following command in the terminal or command line to see the full list of ROS topics from the ROS master:

rostopic list

If you do not see the topic listed that you are trying to use in the "rossubscriber" function, then please ensure you are using the correct TurtleBot in your Gazebo simulation. For example, if you are trying to subscribe to a topic related to a Raspberry Pi camera, you'll need to ensure that you're using TurtleBot3 Waffle Pi and not TurtleBot3 Burger.

Please refer to the TurtleBot user manual for more information:

https://emanual.robotis.com/docs/en/platform/turtlebot3/basic_operation/#basic-operation