Writing a ROS-PX4 application

Let's now create a new package in which we will store all the source and launch files needed to send and receive data from the simulated UAV using ROS. Enter your ROS source workspace and use the following command:

catkin_create_project px4_ros_ctrl roscpp mavros_msgs  geometry_msgs

As you can see, this package depends from the mavros_msgs. This will be used to retrieve data from the UAV. Here, we will discuss the ROS node that controls the vehicle. The complete code can be found in the book source code and it is contained into the src/px4_ctrl_example.cpp source file.

To achieve our goal, we need to perform the following operations:

1. Arm the quadrotor. Arming the vehicle allows the motors to start spinning. This can be done using mavros through ROS services. The /mavros/cmd/arming service can be used.
2. Switch to OFFBOARD mode. After that, the motors should start to spin and we can send input to the UAV. To accept external...