Using an Input, Configuration Parameter, and Output

Table of Contents

• Overview
• Step 1: Define the Control Class with Input, Configuration Parameter, and Output
• Step 2: JSON Configuration for the Input, Output, and Configuration Parameter
• Step 3: Implement the Xentara Data Point and Configuration Logic
• Conclusion

Overview

In this tutorial, we will update our control to use one input, one configuration parameter, and one output. The step function will read the input, multiply it by the configuration parameter, and write the result to the output. This demonstrates how to use a configuration parameter to influence control behavior dynamically.

The objectives of this tutorial are to:

• Define an input and an output as Xentara data points.
• Introduce a configuration parameter that modifies control behavior.
• Implement the logic to read the input, apply the configuration parameter, and write to the output.

Step 1: Define the Control Class with Input, Configuration Parameter, and Output

In this version of the control class, we define one xentara::Float64Input for the input, an integer configuration parameter, and one xentara::Float64Output for the output.

Here is the updated code for ConfigMultiplierControl.hpp:

#pragma once
 
#include <xentara/cpp-control.h>
 
class ConfigMultiplierControl final : public xentara::Control
{
public:
    void initialize(xentara::InitContext &context) override;
 
    void step(xentara::RunContext &context) override;
 
private:
    /// Xentara-managed input data point
    xentara::Float64Input input;
 
    /// Xentara-managed output data point
    xentara::Float64Output output;
 
    /// Configuration parameter for multiplication
    int configParameter {1};
};

Step 2: JSON Configuration for the Input, Output, and Configuration Parameter

The JSON configuration file below configures the data points and the configuration parameter for this control. The configuration parameter (multiplier) is defined in the "parameters" section, with Input and Output as Xentara data points specified by name.

{
  "children": [
    {
      "@Skill.CPP.Control": {
        "name": "Control",
        "UUID": "f6e82386-db77-48af-9e3a-14f821a07a15",
        "controlPath": "libcontrol.so",
        "parameters": {
          "multiplier": 2,
          "input": "Input",
          "output": "Output"
        }
      }
    },
    {
      "@Skill.SignalFlow.Register": {
        "name": "Input",
        "UUID": "60729f3b-e54e-4860-ad8a-12614a4b10d5",
        "defaultValue": [ "float64", 125.85 ]
      }
    },
    {
      "@Skill.SignalFlow.Register": {
        "name": "Output",
        "UUID": "a1c781ee-af86-4a40-8ea7-49ee9e3a3942",
        "defaultValue": [ "float64", 0.0 ]
      }
    },
    {
      "@Track": {
        "name": "Control Track",
        "UUID": "fb0a26f8-7d84-4af9-9345-4145263d09c7",
        "children": [
          {
            "@Timer": {
              "name": "Timer",
              "UUID": "e6580c24-dbf9-43a0-aa81-c5ed8da6f734",
              "period": "50ms"
            }
          },
          {
            "@Pipeline": {
              "name": "Pipeline",
              "UUID": "040f156e-2744-4008-8195-cd7f17078668",
              "triggers": [
                "Control Track.Timer.expired"
              ],
              "checkpoints": [
                {},
                {}
              ],
              "segments": [
                {
                  "start": 0,
                  "end": 1,
                  "tasks": [
                    {
                      "function": "Control.step"
                    }
                  ]
                }
              ]
            }
          }
        ]
      }
    }
  ]
}

In this configuration:

• Input and Output are Xentara-managed data points.
• multiplier is the configuration parameter, with a value of 2, which is used in the initialize function to modify control behavior.

Step 3: Implement the Xentara Data Point and Configuration Logic

In the implementation file, ConfigMultiplierControl.cpp, we will initialize the input and output data points and retrieve the configuration parameter in the initialize method. The step function will then read the input, multiply it by the configuration parameter, and write the result to the output.

Here is the updated code for ConfigMultiplierControl.hpp:

#include "ConfigMultiplierControl.hpp"
 
/// Registers the ConfigMultiplierControl with Xentara.
const xentara::ControlExporter<ConfigMultiplierControl> kConfigMultiplierControl;
 
void ConfigMultiplierControl::initialize(xentara::InitContext &context)
{
    // Initialize input and output data points
    input = context.config().getDataPoint("input");
    output = context.config().getDataPoint("output");
 
    // Retrieve the configuration parameter
    configParameter = context.config().getInt("multiplier");
}
 
void ConfigMultiplierControl::step(xentara::RunContext &context)
{
    // Read the input value
    auto inputValue = input.read(context);
 
    // Multiply the value
    double multipliedValue = inputValue * configParameter;
 
    // Multiply by configuration parameter and write to output
    output.write(context, multipliedValue);
}

Conclusion

In this tutorial, we introduced a configuration parameter that influences control behavior by modifying an input value before writing it to the output. This setup demonstrates how to use configuration values alongside inputs and outputs to customize control logic, creating a flexible and dynamic control component in Xentara.