11 week HW (2) Parameter programming

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review

https://needs-searcher.tistory.com/181

6 week HW Parameter control using turtlesim node

 

 

command list

see a list of parma

$ ros2 param list

 

get value of a param

$ ros2 param get <node_name> <parameter_name>

 

set value

$ ros2 param set <node_name> <parameter_name> <value>

 

 

1. make a package

$ ros2 pkg create python_parameters --build-type ament_python --dependencies rclpy

 

2. write code

import rclpy
from rclpy.node import Node
from rclpy.exceptions import ParameterNotDeclaredException
 
class MinimalParam(Node):
    def __init__(self):
        super().__init__('minimal_param_node')
        timer_period = 2 # every 2 sec
 
        # to call callback func at custum hertz
        self.timer = self.create_timer(timer_period, self.timer_callback)
 
        self.declare_parameter('my_parameter', 'world') # param name, param value
 
    def timer_callback(self):
        # first, get param from the node and assign value to my_param
        my_param = self.get_parameter('my_parameter').get_parameter_value().string_value
 
        self.get_logger().info('Hello %s!' % my_param)
 
def main():
    rclpy.init()
    node = MinimalParam()
 
    try:
        rclpy.spin(node)
    except KeyboardInterrupt:
        node.get_logger().info('This node is finished by keboard interrupt')
    finally:
        node.destroy_node()
        rclpy.shutdown()
 
if __name__ == '__main__':
    main()

 

 

3. revise package.xml file

4. revise the setup.py file

** entry_point**

 

note that the node's executable name is 'param_talker'

 

5. build and run

6. check the created parameter

 

see a list of parma

$ ros2 param list

get value of a param

$ ros2 param get <node_name> <parameter_name>

set value

$ ros2 param set <node_name> <parameter_name> <value>

 

7. Add a parameter

import rclpy
from rclpy.node import Node
from rclpy.exceptions import ParameterNotDeclaredException
 
class MinimalParam(Node):
    def __init__(self):
        super().__init__('minimal_param_node')
        timer_period = 2
 
        # to call callback func at custum hertz
        self.timer = self.create_timer(timer_period, self.timer_callback)
 
        self.declare_parameter('my_parameter', 'world') # param name, param value
        self.declare_parameter('num_parameter', 1) # another param
 
    def timer_callback(self):
        # first, get param from the node and assign value to my_param
        my_param = self.get_parameter('my_parameter').get_parameter_value().string_value
        num_param = self.get_parameter('num_parameter').get_parameter_value().integer_value
 
        self.get_logger().info('Hello %s!, Num: %d,' % (my_param, num_param))
 
def main():
    rclpy.init()
    node = MinimalParam()
 
    try:
        rclpy.spin(node)
    except KeyboardInterrupt:
        node.get_logger().info('This node is finished by keboard interrupt')
    finally:
        node.destroy_node()
        rclpy.shutdown()
 
if __name__ == '__main__':
    main()

 

add two lines

self.declare_parameter('num_parameter', 1) 

self.get_logger().info('Hello %s!, Num: %d,' % (my_param, num_param))

 

8. test

9. check in rqt and revise the param value

at rqt - Plugins-Configuration-Dynamic reconfigure

 

 

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