Vision Subsystem

The Vision Subsystem will house the core of the code. It is always a good idea to have a Vision subsystem that will hold all the getters and setters for the vision on the robot.

VisionSubsystem.java

Imports

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package frc.robot.subsystems;

import edu.wpi.first.networktables.NetworkTable;
import edu.wpi.first.networktables.NetworkTableEntry;
import edu.wpi.first.networktables.NetworkTableInstance;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
import edu.wpi.first.wpilibj2.command.SubsystemBase;

  • Line 1 is the package setup, and will assign this class to the package.

  • Line 3 is the import for networktables; this allows us to talk with the vision Scripts.

  • Line 4 is the import for network table entries and allows us to read the data from the table.

  • Line 5 is the import for the networktables instance and is used to get the table.

  • Line 6 is the import for SmartDashboard, which will be used to put values for user display.

  • Line 7 is the import for SubsystemBase, which is required to have this class become a subsystem.

Class

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public class VisionSubsystem extends SubsystemBase

  • Line 9 creates the class VisionSubsystem and extends SubsystemBase to have this class be a subsystem.

Objects

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private NetworkTableInstance inst = NetworkTableInstance.getDefault();
private NetworkTable table = inst.getTable("Vision");
private NetworkTableEntry data;

  • Line 11 creates the NetworkTableInstance

  • Line 12 creates the table

  • Line 13 creates the table entry reference

Constructor

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public VisionSubsystem()
{
    SmartDashboard.putBoolean("Get New Barcode", false);
}

  • Line 15 is the constructor and will create the VisionSubsystem when called.

  • Line 17 Will create an entry in the smartdashboard called Get New Barcode and sets its default value to false.

Setter

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public void readBarcode()
{
    table.getEntry("readBarcode").setBoolean(true);
}

  • Line 20 is the setter that is called when a new barcode should be read.

  • Line 22 will update the readBarcode flag in networktables to true. This, in turn, will tell the vision scripts to read a new barcode and update the data keys.

Getter

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public void printBarcode()
{
    data = table.getEntry("barcodeData");
    SmartDashboard.putString("Barcode Data", data.getString("Nothing was read"));
}

  • Line 25 is the method that will be called to get the current value of the barcodeData entry.

  • Line 27 assigns the entry to the data object.

  • Line 28 places the string value of data to the dashboard.

Periodic Loop

The periodic loop is used to check the current value of the barcodeData entry for every robot loop.

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@Override
public void periodic()
{
    printBarcode();
}

  • Line 31 is the required Override to tell the compiler to use this periodic method and not the one built into SubsystemBase.

  • Line 32 is the periodic method.

  • Line 34 will call the printBarcode method every robot loop.

Full Subsystem Code

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package frc.robot.subsystems;

import edu.wpi.first.networktables.NetworkTable;
import edu.wpi.first.networktables.NetworkTableEntry;
import edu.wpi.first.networktables.NetworkTableInstance;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
import edu.wpi.first.wpilibj2.command.SubsystemBase;

public class VisionSubsystem extends SubsystemBase
{
    private NetworkTableInstance inst = NetworkTableInstance.getDefault();
    private NetworkTable table = inst.getTable("Vision");
    private NetworkTableEntry data;

    public VisionSubsystem()
    {
        SmartDashboard.putBoolean("Get New Barcode", false);
    }

    public void readBarcode()
    {
        table.getEntry("readBarcode").setBoolean(true);
    }

    public void printBarcode()
    {
        data = table.getEntry("barcodeData");
        SmartDashboard.putString("Barcode Data", data.getString("Nothing was read"));
    }

    @Override
    public void periodic()
    {
        printBarcode();
    }
}