Vision Command

The Vision Command is used to tell the VisionSubsystem code what to do and when to do it.

VisionCommand.java

Imports

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package frc.robot.commands;

import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
import edu.wpi.first.wpilibj2.command.CommandBase;
import frc.robot.RobotContainer;
import frc.robot.subsystems.VisionSubsystem;

  • Line 1 adds VisionCommand to the correct package.

  • Line 3 imports the SmartDashboard, used to display data and get a button input.

  • Line 4 imports the CommandBase, used to make this class part of the command framework.

  • Line 5 imports the RobotContainer so that instances of subsystems can be shared.

  • Line 6 imports the VisionSubsystem which is needed so the command can operate.

Class

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public class VisionCommand extends CommandBase

  • Line 8 creates the class for VisionCommand and extends the CommandBase framework with it.

Objects, Instances, and Variables

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    private static final VisionSubsystem vision = RobotContainer.vision;

    boolean getNewBarcode;

  • Line 10 creates the VisionSubsystem object and assigns the instance of VisionSubsystem from the one created in RobotContainer.

  • Line 12 is a simple boolean flag used to see if the user wants to get a new barcode reading.

Constructor

Note

After adding this step, there will be an error shown. Ignore this error as it will be fixed in RobotContainer part 2.

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public VisionCommand ()
{
    addRequirements(vision);
}

  • Line 14 is the constructor for the VisionCommand class.

  • Line 16 tells the CommandBase that VisionCommand requires a VisionSubsystem instance to run.

Initialize

If there is any code that needs to be initialized, it will go in here. But as that is not required, this is an empty method.

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@Override
public void initialize(){}

Execute

The execute method is what is called every time the command is called. Meaning that the code to be run continuously should be in here.

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@Override
public void execute()
{
    getNewBarcode = SmartDashboard.getBoolean("Get New Barcode", false);

    if (getNewBarcode)
    {
        vision.readBarcode();
        SmartDashboard.putBoolean("Get New Barcode", false);
    }
}

  • Line 23 is the execute method.

  • Line 25 assigns the boolean value taken from Get New Barcode on the dashboard to getNewBarcode. The second parameter in the getBoolean call is the default value if nothing can be found.

  • Line 27 is a conditional statement that checks if getNewBarcode is true. (Button was pushed)

  • Line 29 will call the readBarcode method from VisionSubsystem, which in turn will call the scripts on the VMX.

  • Line 30 sets the getNewBarcode button on the dashboard to false to prevent a continuous call to the scripts when only one call is required.

End

The end method is called when the command is interrupted or is finished as there are no motors or anything safety-related called by this command. The end method can remain blank.

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@Override
public void end(boolean interrupted){}

isFinished

Is finished is a method that is used to create an end condition for the command. As this command should run all the time and never end, a false statement will be returned.

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@Override
public boolean isFinished()
{
    return false;
}

Full VisionCommand Code

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package frc.robot.commands;

import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
import edu.wpi.first.wpilibj2.command.CommandBase;
import frc.robot.RobotContainer;
import frc.robot.subsystems.VisionSubsystem;

public class VisionCommand extends CommandBase
{
    private static final VisionSubsystem vision = RobotContainer.vision;

    boolean getNewBarcode;

    public VisionCommand ()
    {
        addRequirements(vision);
    }

    @Override
    public void initialize(){}

    @Override
    public void execute()
    {
        getNewBarcode = SmartDashboard.getBoolean("Get New Barcode", false);

        if (getNewBarcode)
        {
            vision.readBarcode();
            SmartDashboard.putBoolean("Get New Barcode", false);
        }
    }

    @Override
    public void end(boolean interrupted){}

    @Override
    public boolean isFinished()
    {
        return false;
    }
}