Hands-On ROS for Robotics Programming

Inspecting published topics and messages

Now that we've identified the three topics, let's take a look at them and get some robot-specific information:

1. To find the last five values of the battery, run the following command in a Terminal. This will allow you to inspect the /battery_voltage topic:

T1 $ rostopic echo battery_voltage -n 5data: 9.568---data: 9.551---data: 9.594---data: 9.568---data: 9.586

You can infer that the voltage is about 9.6V on average, which means the batteries are charged.

2. Let's investigate how this topic is built:

T1 $ rostopic info battery_voltage      Type: std_msgs/Float64

It uses the std_msgs/Float64 message type, which corresponds to a floating-point number that's 64 bits size. This message type is part of the ROS ...