First ROS 2 node: Publisher + CMakeLists + launch.py

1. Edit `hello.py`

class HelloDrone(Node):

    def __init__(self):
        # node's name
        super().__init__('hello_drone')

        # Publishing VL53L0X x6 data — mock
        self.pub_perimeter = self.create_publisher(
            Float32MultiArray,    # type of data
            '/drone/perimeter',   # name of param
            10                    # save in store if not readed
        )

    def tick():
        ...

One moment about ROS 2: to build nodes, I use a venv for all packages. But to run nodes — I have to deactivate the venv, because ROS 2 doesn’t play nice with venv. See venv ↔ ROS 2 / colcon.

2. Rebuild + run

3. Look at the topics

ros2 topic list

4. Read data from a topic

ros2 topic echo /drone/altitud

5. Frequency

ros2 topic hz /drone/perimeter

You should see ~1 Hz — because our timer fires once per second:

average rate: 1.000        min: 1.000s max: 1.000s std dev: 0.00044s window: 2
average rate: 1.000        min: 1.000s max: 1.000s std dev: 0.00035s window: 4

Adding a new node (`sensor_monitor.py`)

Create the node sensor_monitor.py.
Add to CMakeLists.txt, after # Register nodes:

install(PROGRAMS
  drone_sim/sensor_monitor.py
  RENAME sensor_monitor
  DESTINATION lib/${PROJECT_NAME}
)

For testing, set one critical param in hello.py:

perimeter.data = [1.2, 0.25, 1.5, 2.0, 1.1, 0.9]

Launcher

Create simulation/src/drone_sim/launch/drone.launch.py.

Build → run:

ros2 launch drone_sim drone.launch.py

The launcher usually shows up in the terminal without color. You can turn that on:

RCUTILS_COLORIZED_OUTPUT=1

1. Edit hello.py