Utility methods

Snapshot and capture

`triggerSnapshot`

Triggers a snapshot by incrementing the snapshot counter in NetworkTables. The Limelight rate-limits snapshot captures to once per 10 frames.

LimelightHelpers.triggerSnapshot("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

`setRewindEnabled`

Enables or pauses the rewind buffer recording. When enabled, the camera continuously records frames to a rolling buffer.

// Start recording
LimelightHelpers.setRewindEnabled("limelight", true);

// Pause recording
LimelightHelpers.setRewindEnabled("limelight", false);

limelightName

string

required

Name of the Limelight NetworkTables table.

enabled

boolean

required

true to enable rewind recording, false to pause it.

`triggerRewindCapture`

Triggers a rewind capture of the specified duration. The maximum duration is 165 seconds; values above this are clamped. The Limelight rate-limits this operation internally.

// Capture the last 10 seconds
LimelightHelpers.triggerRewindCapture("limelight", 10.0);

limelightName

string

required

Name of the Limelight NetworkTables table.

durationSeconds

double

required

Duration of the rewind capture in seconds. Clamped to a maximum of 165.0.

Pose conversion

These static utility methods convert between the 6-element double[] format used by NetworkTables and WPILib geometry types. The array format is always [x, y, z, roll, pitch, yaw] where translations are in meters and angles are in degrees.

`toPose3D`

Converts a 6-element pose array to a Pose3d object.

double[] poseArray = LimelightHelpers.getBotPose_wpiBlue("limelight");
Pose3d pose3d = LimelightHelpers.toPose3D(poseArray);

System.out.println("X: " + pose3d.getX());
System.out.println("Yaw: " + pose3d.getRotation().getZ()); // radians

inData

double[]

required

6-element array [x, y, z, roll, pitch, yaw]. Angles must be in degrees.

returns

Pose3d

A Pose3d with translation in meters and rotation in radians (converted internally). Returns an empty Pose3d if the array has fewer than 6 elements.

`toPose2D`

Converts a 6-element pose array to a Pose2d object. Only x, y, and yaw are used; z, roll, and pitch are ignored.

double[] poseArray = LimelightHelpers.getBotPose_wpiBlue("limelight");
Pose2d pose2d = LimelightHelpers.toPose2D(poseArray);

System.out.println("X: " + pose2d.getX());
System.out.println("Yaw: " + pose2d.getRotation().getDegrees() + "°");

inData

double[]

required

6-element array [x, y, z, roll, pitch, yaw]. Angles must be in degrees.

returns

Pose2d

A Pose2d using x, y, and yaw (converted to radians). Returns an empty Pose2d if the array has fewer than 6 elements.

`pose3dToArray`

Converts a Pose3d object to a 6-element array. This is the inverse of toPose3D.

Pose3d pose = new Pose3d(1.0, 2.0, 0.5, new Rotation3d(0, 0, Math.PI / 2));
double[] array = LimelightHelpers.pose3dToArray(pose);
// array = [1.0, 2.0, 0.5, 0.0, 0.0, 90.0]

pose

Pose3d

required

The Pose3d to convert.

returns

double[]

6-element array [x, y, z, roll, pitch, yaw]. Translations are in meters; rotations are in degrees.

`pose2dToArray`

Converts a Pose2d object to a 6-element array. z, roll, and pitch are always 0. This is the inverse of toPose2D.

Pose2d pose = new Pose2d(1.0, 2.0, Rotation2d.fromDegrees(45.0));
double[] array = LimelightHelpers.pose2dToArray(pose);
// array = [1.0, 2.0, 0.0, 0.0, 0.0, 45.0]

pose

Pose2d

required

The Pose2d to convert.

returns

double[]

6-element array [x, y, 0, 0, 0, yaw]. Translations are in meters; yaw is in degrees.

Round-trip pattern

Use pose3dToArray and toPose3D (or their 2D equivalents) when storing or transmitting poses through NT or logging pipelines that require the flat array format:

// Store a known camera offset as an array, then reconstruct later
Pose3d cameraOffset = new Pose3d(0.3, 0.0, 0.2,
    new Rotation3d(0, Math.toRadians(-30), 0));

double[] stored = LimelightHelpers.pose3dToArray(cameraOffset);
// Persist or log `stored` ...

// Reconstruct
Pose3d restored = LimelightHelpers.toPose3D(stored);

// 2D equivalent
Pose2d pose2d = new Pose2d(1.5, 2.0, Rotation2d.fromDegrees(90));
double[] arr2d = LimelightHelpers.pose2dToArray(pose2d);
Pose2d roundTripped = LimelightHelpers.toPose2D(arr2d);

Debugging

`printPoseEstimate`

Prints detailed information about a PoseEstimate to standard output. Useful for quick field-side debugging. Output includes: timestamp (s), latency (ms), tag count, tag span (m), average tag distance (m), average tag area (%), isMegaTag2 flag, and per-fiducial details (ID, txnc, tync, ta, distance to camera/robot, ambiguity).

LimelightHelpers.PoseEstimate estimate =
    LimelightHelpers.getBotPoseEstimate_wpiBlue("limelight");

LimelightHelpers.printPoseEstimate(estimate);
// Pose Estimate Information:
// Timestamp (Seconds): 15.234
// Latency: 12.500 ms
// Tag Count: 2
// Tag Span: 3.12 meters
// Average Tag Distance: 2.45 meters
// Average Tag Area: 4.80% of image
// Is MegaTag2: false
//
// Raw Fiducials Details:
//  Fiducial #1:
//   ID: 7
//   TXNC: -2.34
//   ...

If pose is null, prints "No PoseEstimate available." and returns immediately.

pose

PoseEstimate

required

The PoseEstimate to print. Safe to call with null.

`validPoseEstimate`

Returns true if the PoseEstimate is non-null and contains at least one fiducial result. Use this before passing an estimate to the WPILib pose estimator.

LimelightHelpers.PoseEstimate estimate =
    LimelightHelpers.getBotPoseEstimate_wpiBlue_MegaTag2("limelight");

if (LimelightHelpers.validPoseEstimate(estimate)) {
    poseEstimator.addVisionMeasurement(
        estimate.pose,
        estimate.timestampSeconds
    );
}

pose

PoseEstimate

required

The PoseEstimate to validate.

returns

Boolean

true if pose is non-null and pose.rawFiducials is non-empty. false otherwise.

Network and connection

`getHeartbeat`

Returns a counter that increments once per frame. If this value stops changing, the camera is likely disconnected or has stopped publishing.

double heartbeat = LimelightHelpers.getHeartbeat("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

returns

double

Monotonically increasing frame counter. Verify the camera is alive by checking that this value changes between periodic cycles.

`setupPortForwardingUSB`

Sets up PortForwarder entries so a USB-connected Limelight 3A or 3G is reachable from the driver station or development machine. Call this method once in robotInit(). Do not call it in a periodic loop.

USB index	Forwarded ports	Limelight IP
0	5800–5809	172.29.0.1
1	5810–5819	172.29.1.1
2	5820–5829	172.29.2.1

After calling this method, access the Limelight web interface at roboRIO-<team>-FRC.local:5801 (index 0) or roboRIO-<team>-FRC.local:5811 (index 1).

@Override
public void robotInit() {
    // Single Limelight 3G over USB
    LimelightHelpers.setupPortForwardingUSB(0);

    // Two Limelights over USB
    LimelightHelpers.setupPortForwardingUSB(0);
    LimelightHelpers.setupPortForwardingUSB(1);
}

usbIndex

int

required

Zero-based index of the USB-connected Limelight. 0 forwards ports 5800–5809 to 172.29.0.1; 1 forwards ports 5810–5819 to 172.29.1.1, and so on.

`Flush`

Calls NetworkTableInstance.getDefault().flush() to immediately push pending NT writes to the network. Used internally by SetRobotOrientation to ensure the orientation value reaches the camera before the next pose read.

LimelightHelpers.Flush();

Call this manually after SetRobotOrientation_NoFlush when you want to control flush timing yourself.

IMU

`getIMUData`

Returns the current IMU data from the Limelight as an IMUData object. Returns an all-zeros object if the data is unavailable or the raw array has fewer than 10 elements.

LimelightHelpers.IMUData imu = LimelightHelpers.getIMUData("limelight");

System.out.println("Robot Yaw: " + imu.robotYaw);
System.out.println("Pitch: "     + imu.Pitch);
System.out.println("Roll: "      + imu.Roll);
System.out.println("Gyro X: "    + imu.gyroX);
System.out.println("Accel Z: "   + imu.accelZ);

The IMUData fields map to the raw NT array as follows:

Field	Array index
`robotYaw`	0
`Roll`	1
`Pitch`	2
`Yaw`	3
`gyroX`	4
`gyroY`	5
`gyroZ`	6
`accelX`	7
`accelY`	8
`accelZ`	9

limelightName

string

required

Name of the Limelight NetworkTables table.

returns

IMUData

IMUData object populated from the imu NetworkTables array. All fields are 0.0 if data is unavailable.

Data Classes

Methods

Snapshot and capture

`triggerSnapshot`

`setRewindEnabled`

`triggerRewindCapture`

Pose conversion

`toPose3D`

`toPose2D`

`pose3dToArray`

`pose2dToArray`

Round-trip pattern

Debugging

`printPoseEstimate`

`validPoseEstimate`

Network and connection

`getHeartbeat`

`setupPortForwardingUSB`

`Flush`

IMU

`getIMUData`

Build docs developers (and LLMs) love

Data Classes

Methods

​Snapshot and capture

​triggerSnapshot

​setRewindEnabled

​triggerRewindCapture

​Pose conversion

​toPose3D

​toPose2D

​pose3dToArray

​pose2dToArray

​Round-trip pattern

​Debugging

​printPoseEstimate

​validPoseEstimate

​Network and connection

​getHeartbeat

​setupPortForwardingUSB

​Flush

​IMU

​getIMUData

Build docs developers (and LLMs) love

Snapshot and capture

`triggerSnapshot`

`setRewindEnabled`

`triggerRewindCapture`

Pose conversion

`toPose3D`

`toPose2D`

`pose3dToArray`

`pose2dToArray`

Round-trip pattern

Debugging

`printPoseEstimate`

`validPoseEstimate`

Network and connection

`getHeartbeat`

`setupPortForwardingUSB`

`Flush`

IMU

`getIMUData`