Java – FRC – Limelight Vision – Basic Information Read

The code below will help you to be able read basic information from your Limelight Vision camera.

If you haven’t already read the documentation it’s a good idea to start there -> http://docs.limelightvision.io/en/latest/

Start with a new “Timed Robot” template project and add a few imports

import edu.wpi.first.networktables.NetworkTable;
import edu.wpi.first.networktables.NetworkTableEntry;
import edu.wpi.first.networktables.NetworkTableInstance;

Within the “public void teleopPeriodic() {” put the below in to start reading data from the Limelight Vision camera

    Limelight Data Start
    // get the default instance of NetworkTables
    NetworkTableInstance inst = NetworkTableInstance.getDefault();
    // get a reference to the subtable called "datatable"
    NetworkTable table = inst.getTable("limelight");

    inst.startClientTeam(3535); // Make sure you set this to your team number

    inst.startDSClient(); // recommended if running on DS computer; this gets the robot IP from the DS

    // NetworkTableEntry TeamEntry = table.getEntry("tx");
    NetworkTableEntry xEntry = table.getEntry("tx");
    NetworkTableEntry yEntry = table.getEntry("ty");
    NetworkTableEntry aEntry = table.getEntry("ta");
    NetworkTableEntry lEntry = table.getEntry("tl");
    NetworkTableEntry vEntry = table.getEntry("tv");
    NetworkTableEntry sEntry = table.getEntry("ts");

    NetworkTableEntry tshortEntry = table.getEntry("tshort");
    NetworkTableEntry tlongEntry = table.getEntry("tlong");
    NetworkTableEntry thorEntry = table.getEntry("thor");
    NetworkTableEntry tvertEntry = table.getEntry("tvert");
    NetworkTableEntry getpipeEntry = table.getEntry("getpipe");
    NetworkTableEntry camtranEntry = table.getEntry("camtran");
    NetworkTableEntry ledModeEntry = table.getEntry("ledMode");

    // double tx = xEntry.getDouble(0.0);
    double tx = xEntry.getDouble(0.0); // Horizontal Offset From Crosshair To Target (-27 degrees to 27 degrees)
    double ty = yEntry.getDouble(0.0); // Vertical Offset From Crosshair To Target (-20.5 degrees to 20.5 degrees)
    double ta = aEntry.getDouble(0.0); // Target Area (0% of image to 100% of image)
    double tl = lEntry.getDouble(0.0); // The pipeline’s latency contribution (ms) Add at least 11ms for image capture
                                       // latency.
    double tv = vEntry.getDouble(0.0); // Whether the limelight has any valid targets (0 or 1)
    double ts = sEntry.getDouble(0.0); // Skew or rotation (-90 degrees to 0 degrees)

    // double tshort = tshortEntry.getString(); // Sidelength of shortest side of
    // the fitted bounding box (pixels)
    // double tlong = tlong // Sidelength of longest side of the fitted bounding box
    // (pixels)
    // double thor = thor // Horizontal sidelength of the rough bounding box (0 -
    // 320 pixels)
    // double tvert = tvert // Vertical sidelength of the rough bounding box (0 -
    // 320 pixels)
    // double getpipe = getpipe // True active pipeline index of the camera (0 .. 9)
    // double camtran = camtran // Results of a 3D position solution, 6 numbers:
    // Translation (x,y,y) Rotation(pitch,yaw,roll)

    //ledModeEntry.setNumber(0); // use the LED Mode set in the current pipeline
    ledModeEntry.setNumber(1); // force off
    //ledModeEntry.setNumber(2); // force blink
    //ledModeEntry.setNumber(3); // force on

    //System.out.println("X: " + tx);
    //System.out.println("Y: " + ty);
    //System.out.println("A: " + ta);
    //System.out.println("L: " + tl);
    //System.out.println("V: " + tv);
    //System.out.println("S: " + tv);

    // post to smart dashboard periodically
    SmartDashboard.putNumber("Limelight X", tx);
    SmartDashboard.putNumber("Limelight Y", ty);
    SmartDashboard.putNumber("Limelight Area", ta);
    SmartDashboard.putNumber("Limelight Latency", tl);
    SmartDashboard.putNumber("Limelight Valid Target", tv);
    SmartDashboard.putNumber("Limelight Skew", ts);

    // Limelight Data End

Provided everything is running correctly you should be able to get updated numbers in a SmartDashboard