105 lines
3.4 KiB
Markdown
105 lines
3.4 KiB
Markdown
|
# ROS 2 Parameters
|
||
|
|
## Overview of ROS 2 Parameters
|
||
|
|
In ROS 2, a **node parameter** is a configurable value used to adjust a node's behavior without modifying its code. Parameters are important because they provide flexibility, allowing dynamic tuning and reusability of nodes across different scenarios. For instance say you had a ROS node that took data from a USB camera and published it to a topic. You could use parameters to set the frame rate, USB port, and color depth.
|
||
|
|
|
||
|
|
## ROS 2 Parameters CLI
|
||
|
|
The following command are help full when you are debugging or tracking down a problem.
|
||
|
|
|
||
|
|
Command to list parameters
|
||
|
|
```bash
|
||
|
|
ros2 param list /node_name
|
||
|
|
```
|
||
|
|
|
||
|
|
Command to get parameter value
|
||
|
|
```bash
|
||
|
|
ros2 param get /node_name param_name
|
||
|
|
```
|
||
|
|
|
||
|
|
## Adding ROS 2 Parameters
|
||
|
|
Adding Parameters to a ROS 2 program is not that hard. Below you can see the steps.
|
||
|
|
|
||
|
|
=== "Python"
|
||
|
|
```python title="number_publisher.py" linenums="1" hl_lines="11 12 14 15"
|
||
|
|
#!/usr/bin/env python3
|
||
|
|
import rclpy
|
||
|
|
from rclpy.node import Node
|
||
|
|
|
||
|
|
from example_interfaces.msg import Int64
|
||
|
|
|
||
|
|
|
||
|
|
class NumberPublisherNode(Node):
|
||
|
|
def __init__(self):
|
||
|
|
super().__init__("number_publisher")
|
||
|
|
self.declare_parameter("number_to_publish", 2)
|
||
|
|
self.declare_parameter("publish_frequency", 1.0)
|
||
|
|
|
||
|
|
self.number_ = self.get_parameter("number_to_publish").value
|
||
|
|
self.publish_frequency_ = self.get_parameter("publish_frequency").value
|
||
|
|
|
||
|
|
self.number_publisher_ = self.create_publisher(Int64, "number", 10)
|
||
|
|
self.number_timer_ = self.create_timer(1.0 / self.publish_frequency_, self.publish_number)
|
||
|
|
self.get_logger().info("Number publisher has been started.")
|
||
|
|
|
||
|
|
def publish_number(self):
|
||
|
|
msg = Int64()
|
||
|
|
msg.data = self.number_
|
||
|
|
self.number_publisher_.publish(msg)
|
||
|
|
|
||
|
|
|
||
|
|
def main(args=None):
|
||
|
|
rclpy.init(args=args)
|
||
|
|
node = NumberPublisherNode()
|
||
|
|
rclpy.spin(node)
|
||
|
|
rclpy.shutdown()
|
||
|
|
|
||
|
|
|
||
|
|
if __name__ == "__main__":
|
||
|
|
main()
|
||
|
|
```
|
||
|
|
|
||
|
|
|
||
|
|
=== "C++"
|
||
|
|
|
||
|
|
```cpp title="number_publisher.cpp" linenums="1" hl_lines="9 10 12 13"
|
||
|
|
#include "rclcpp/rclcpp.hpp"
|
||
|
|
#include "example_interfaces/msg/int64.hpp"
|
||
|
|
|
||
|
|
class NumberPublisherNode : public rclcpp::Node
|
||
|
|
{
|
||
|
|
public:
|
||
|
|
NumberPublisherNode() : Node("number_publisher")
|
||
|
|
{
|
||
|
|
this->declare_parameter("number_to_publish", 2);
|
||
|
|
this->declare_parameter("publish_frequency", 1.0);
|
||
|
|
|
||
|
|
number_ = this->get_parameter("number_to_publish").as_int();
|
||
|
|
double publish_frequency = this->get_parameter("publish_frequency").as_double();
|
||
|
|
|
||
|
|
number_publisher_ = this->create_publisher<example_interfaces::msg::Int64>("number", 10);
|
||
|
|
number_timer_ = this->create_wall_timer(std::chrono::milliseconds((int)(1000.0 / publish_frequency)),
|
||
|
|
std::bind(&NumberPublisherNode::publishNumber, this));
|
||
|
|
RCLCPP_INFO(this->get_logger(), "Number publisher has been started.");
|
||
|
|
}
|
||
|
|
|
||
|
|
private:
|
||
|
|
void publishNumber()
|
||
|
|
{
|
||
|
|
auto msg = example_interfaces::msg::Int64();
|
||
|
|
msg.data = number_;
|
||
|
|
number_publisher_->publish(msg);
|
||
|
|
}
|
||
|
|
|
||
|
|
int number_;
|
||
|
|
rclcpp::Publisher<example_interfaces::msg::Int64>::SharedPtr number_publisher_;
|
||
|
|
rclcpp::TimerBase::SharedPtr number_timer_;
|
||
|
|
};
|
||
|
|
|
||
|
|
int main(int argc, char **argv)
|
||
|
|
{
|
||
|
|
rclcpp::init(argc, argv);
|
||
|
|
auto node = std::make_shared<NumberPublisherNode>();
|
||
|
|
rclcpp::spin(node);
|
||
|
|
rclcpp::shutdown();
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
```
|