QoS profile for ROS2 in Python

R_mcc · July 3, 2023, 10:04pm

Hello, I am looking to do some offboard control and need to subscribe to the “/fmu/out/vehicle_odometry” topic. However as detailed in the documentation, the default QoS profile for ROS2 subscribers is incompatible with PX4’s publishers.The documentation does give example code for changing this QoS profile, however it is in C++.

If anyone can show me what creating this custom QoS profile in Python would look like I would be very grateful.

Thanks!

Benja · July 4, 2023, 12:07am

Hi @R_mcc !
You can take a look at the offboard control example in python!

github.com

PX4/px4_ros_com/blob/e18248db6211350e6a418cb08ae38f64c314a2f4/src/examples/offboard_py/offboard_control.py

import rclpy
from rclpy.node import Node
from rclpy.qos import QoSProfile, ReliabilityPolicy, HistoryPolicy, DurabilityPolicy
from px4_msgs.msg import OffboardControlMode, TrajectorySetpoint, VehicleCommand, VehicleLocalPosition, VehicleStatus


class OffboardControl(Node):
    """Node for controlling a vehicle in offboard mode."""

    def __init__(self) -> None:
        super().__init__('offboard_control_takeoff_and_land')

        # Configure QoS profile for publishing and subscribing
        qos_profile = QoSProfile(
            reliability=ReliabilityPolicy.BEST_EFFORT,
            durability=DurabilityPolicy.TRANSIENT_LOCAL,
            history=HistoryPolicy.KEEP_LAST,
            depth=1
        )

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R_mcc · July 5, 2023, 4:27pm

Hello,

I didn’t realize that package had been updated with newer examples! This works perfectly for me, thank you so much!