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ROS2 parameters

Parameters Hierarchy

  • Declare node with parameters name that using dot(.) to describe the yaml struct
  • Create struct yaml file
params.yaml
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/param_demo:
  ros__parameters:
    camera:
      resolution:
        width: 640
    use_sim_time: false
simple_node.py
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#!/usr/bin/env python3

import rclpy
from rclpy.node import Node

NAME = "param_demo"

class ParamDemo(Node):
    def __init__(self):
        super().__init__(NAME)
        self.param1 = self.declare_parameter("camera.resolution.width", 640)
        self.t = self.create_timer(1.0, self.timer_handler)

    def timer_handler(self):
        self.get_logger().info(f"{self.get_parameter('camera.resolution.width').value}")

def main(args=None):
    rclpy.init(args=args)
    node = ParamDemo()
    rclpy.spin(node)

    node.destroy_node()
    rclpy.shutdown()


if __name__ == "__main__":
    main()
run node with parameter file
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ros2 run my_package my_node --ros-args --params-file params.yaml

usage

alt text

update from cli
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ros2 param set /param_demo camera.resolution.width 1200

update string node with numeric value

The failure happens only if we set the parameter value as string numeric (number in Quotation marks)

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# parameter declaration
self.param1 = self.declare_parameter("param1", value="1")

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ros2 param set /param_demo param1 "12"
# 
Setting parameter failed: Wrong parameter type, expected 'Type.STRING' got 'Type.INTEGER'

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# use double quotation
ros2 param set /param_demo param1 '"12"'