LimelightResults

LimelightResults is the deserialized form of the Limelight’s full JSON output. It is returned by LimelightHelpers.getLatestResults(limelightName), which fetches the json NetworkTables entry and parses it with Jackson.

LimelightResults results = LimelightHelpers.getLatestResults("limelight");

For high-frequency robot loops, prefer the direct NetworkTables methods — getRawFiducials, getBotPoseEstimate_wpiBlue, getTX, etc. — over getLatestResults(). JSON parsing adds measurable latency (latency_jsonParse records the cost per call) and allocates garbage on every invocation. Reserve getLatestResults() for tasks where you need the full result set: iterating all detector outputs, reading barcode data, or logging diagnostics.

Top-level fields

error

String

Non-empty if JSON parsing failed or the NT entry was empty. Always check this field before using any other data. Example values: "lljson error: empty json", "lljson error: <Jackson message>".

pipelineID

double

Active pipeline index at the time the frame was processed. Maps to JSON key pID.

latency_pipeline

double

Pipeline processing latency in milliseconds. Maps to JSON key tl.

latency_capture

double

Image capture latency in milliseconds. Maps to JSON key cl.

latency_jsonParse

double

Time to parse the JSON string in the library, in milliseconds. Set by getLatestResults() after deserialization — not part of the Limelight JSON payload.

timestamp_LIMELIGHT_publish

double

Limelight-side publish timestamp. Maps to JSON key ts.

timestamp_RIOFPGA_capture

double

RoboRIO FPGA timestamp at the moment NetworkTables captured the entry. Maps to JSON key ts_rio.

timestamp_nt

long

NetworkTables timestamp in microseconds. Maps to JSON key ts_nt.

timestamp_sys

long

System timestamp. Maps to JSON key ts_sys.

timestamp_us

long

Microsecond timestamp. Maps to JSON key ts_us.

valid

boolean

Whether the pipeline produced valid results for this frame. Maps to JSON key v (encoded as a number: 0 or 1).

pipelineType

String

Active pipeline type string, e.g. "retro", "apriltag", "neural_detector". Maps to JSON key pTYPE.

Primary target values

double

Horizontal offset from the crosshair to the primary target in degrees.

double

Vertical offset from the crosshair to the primary target in degrees.

tx_nocrosshair

double

Horizontal offset from the camera’s principal point (no crosshair correction) in degrees. Maps to JSON key txnc.

ty_nocrosshair

double

Vertical offset from the camera’s principal point in degrees. Maps to JSON key tync.

double

Primary target area as a percentage of the image (0–100).

Robot pose arrays

Each pose array has 6 elements: [x, y, z, roll, pitch, yaw]. Translation is in meters; angles are in degrees. Use the WPILib Blue variants for new code.

botpose

double[6]

Robot pose in the field-origin coordinate system.

botpose_wpiblue

double[6]

Robot pose in the WPILib Blue alliance coordinate system (origin at the blue alliance wall). Preferred for pose estimator integration.

botpose_wpired

double[6]

Robot pose in the WPILib Red alliance coordinate system.

botpose_tagcount

double

Number of AprilTags used to compute the MegaTag1 pose.

botpose_span

double

Distance in meters between the two outermost contributing tags.

botpose_avgdist

double

Average distance in meters from the camera to contributing tags.

botpose_avgarea

double

Average tag area (% of image) across all contributing tags.

MegaTag2 pose arrays

botpose_orb

double[6]

MegaTag2 robot pose in the field-origin coordinate system.

botpose_orb_wpiblue

double[6]

MegaTag2 robot pose in the WPILib Blue alliance coordinate system.

botpose_orb_wpired

double[6]

MegaTag2 robot pose in the WPILib Red alliance coordinate system.

Pose helper methods

LimelightResults exposes convenience methods to convert the raw arrays to WPILib geometry objects:

Method	Returns	Source array
`getBotPose2d()`	`Pose2d`	`botpose`
`getBotPose2d_wpiBlue()`	`Pose2d`	`botpose_wpiblue`
`getBotPose2d_wpiRed()`	`Pose2d`	`botpose_wpired`
`getBotPose3d()`	`Pose3d`	`botpose`
`getBotPose3d_wpiBlue()`	`Pose3d`	`botpose_wpiblue`
`getBotPose3d_wpiRed()`	`Pose3d`	`botpose_wpired`

Target arrays

targets_Retro

LimelightTarget_Retro[]

Color/retroreflective pipeline targets. Each entry includes ta, tx, ty, tx_pixels, ty_pixels, tx_nocrosshair, ty_nocrosshair, and pose methods (getCameraPose_TargetSpace, getRobotPose_FieldSpace, etc.).

targets_Fiducials

LimelightTarget_Fiducial[]

AprilTag pipeline targets. See LimelightTarget_Fiducial below.

targets_Classifier

LimelightTarget_Classifier[]

Neural classifier pipeline results. Each entry includes className (String), classID (double), confidence (double), zone (double), tx, ty, tx_pixels, ty_pixels.

targets_Detector

LimelightTarget_Detector[]

Neural detector pipeline results. Each entry includes className (String), classID (double), confidence (double), ta, tx, ty, tx_pixels, ty_pixels, tx_nocrosshair, ty_nocrosshair.

targets_Barcode

LimelightTarget_Barcode[]

Barcode pipeline results. See LimelightTarget_Barcode below.

Hardware and diagnostic fields

hardware

HardwareReport

Limelight hardware statistics for the current frame.

Show HardwareReport fields

cameraId

String

Camera model identifier string. Maps to JSON key cid.

cpuUsage

double

CPU utilization percentage (0–100). Maps to JSON key cpu.

ramUsage

double

RAM utilization percentage (0–100). Maps to JSON key ram.

temperature

double

SoC temperature in degrees Celsius. Maps to JSON key temp.

diskFree

double

Free disk space in megabytes. Maps to JSON key dfree.

diskTotal

double

Total disk capacity in megabytes. Maps to JSON key dtot.

imuResults

IMUResults

IMU data from the JSON payload. After parsing, getLatestResults() calls imuResults.parseDataArray() internally, which populates robotYaw, roll, pitch, rawYaw, gyroX/Y/Z, and accelX/Y/Z from the raw data array. For direct NT access without JSON, see getIMUData.

rewindStats

RewindStats

Capture rewind buffer statistics for the current frame.

Show RewindStats fields

bufferUsage

double

Rewind buffer usage as a fraction (0–1).

enabled

int

1 if rewind recording is enabled, 0 if paused.

flushing

int

1 if the buffer is actively flushing to disk.

frameCount

int

Number of frames currently stored in the rewind buffer.

latencyPenalty

int

Latency penalty in milliseconds added by the rewind buffer. Maps to JSON key latpen.

storedSeconds

double

Total duration in seconds currently stored in the rewind buffer.

pythonOutput

double[]

Output values written by a Python snap script running on the Limelight. Maps to JSON key PythonOut.

LimelightTarget_Fiducial fields

fiducialID

double

AprilTag ID. Maps to JSON key fID.

fiducialFamily

String

Tag family string, e.g. "tag36h11". Maps to JSON key fam.

double

Tag area as a percentage of the image.

double

Horizontal offset from the crosshair to the tag center in degrees.

double

Vertical offset from the crosshair to the tag center in degrees.

tx_pixels

double

Horizontal position of the tag center in pixels. Maps to JSON key txp.

ty_pixels

double

Vertical position of the tag center in pixels. Maps to JSON key typ.

tx_nocrosshair

double

Horizontal offset from the camera’s principal point in degrees. Maps to JSON key tx_nocross.

ty_nocrosshair

double

Vertical offset from the camera’s principal point in degrees. Maps to JSON key ty_nocross.

LimelightTarget_Fiducial also exposes the same set of pose methods as LimelightTarget_Retro: getCameraPose_TargetSpace(), getRobotPose_FieldSpace(), getRobotPose_TargetSpace(), getTargetPose_CameraSpace(), getTargetPose_RobotSpace(), and their 2D counterparts. All return Pose3d / Pose2d respectively.

LimelightTarget_Barcode fields

family

String

Barcode symbology, e.g. "QR", "DataMatrix", "Code128". Maps to JSON key fam.

data

String

Decoded text content of the barcode. Maps to JSON key data.

double

Horizontal offset from the crosshair to the barcode center in degrees.

double

Vertical offset from the crosshair to the barcode center in degrees.

tx_pixels

double

Horizontal pixel position of the barcode center. Maps to JSON key txp.

ty_pixels

double

Vertical pixel position of the barcode center. Maps to JSON key typ.

double

Barcode area as a percentage of the image.

corners

double[][]

Corner point coordinates of the barcode bounding polygon. Maps to JSON key pts. Each element is a 2-element array [x, y] in pixel coordinates.

Code example

LimelightResults results = LimelightHelpers.getLatestResults("limelight");

// Guard against parse failures.
if (results.error != null && !results.error.isEmpty()) {
    DriverStation.reportWarning("Limelight JSON error: " + results.error, false);
    return;
}

if (!results.valid) {
    return;
}

// Iterate over all detected fiducial targets.
for (LimelightHelpers.LimelightTarget_Fiducial tag : results.targets_Fiducials) {
    int id = (int) tag.fiducialID;
    double dist = tag.getCameraPose_TargetSpace().getTranslation().getNorm();
    System.out.printf("Tag %d  tx=%.1f°  dist=%.2f m%n", id, tag.tx, dist);
}

// Read barcode data.
for (LimelightHelpers.LimelightTarget_Barcode barcode : results.targets_Barcode) {
    System.out.printf("Barcode [%s]: %s%n", barcode.family, barcode.data);
}

// Check hardware temperature.
if (results.hardware != null && results.hardware.temperature > 70.0) {
    DriverStation.reportWarning("Limelight temperature high: "
        + results.hardware.temperature + "°C", false);
}

// Log JSON parse cost.
SmartDashboard.putNumber("LL/jsonParseMs", results.latency_jsonParse);

Data Classes

Methods

Top-level fields

Primary target values

Robot pose arrays

MegaTag2 pose arrays

Pose helper methods

Target arrays

Hardware and diagnostic fields

LimelightTarget_Fiducial fields

LimelightTarget_Barcode fields

Code example

Build docs developers (and LLMs) love

Data Classes

Methods

​Top-level fields

​Primary target values

​Robot pose arrays

​MegaTag2 pose arrays

​Pose helper methods

​Target arrays

​Hardware and diagnostic fields

​LimelightTarget_Fiducial fields

​LimelightTarget_Barcode fields

​Code example

Build docs developers (and LLMs) love

Top-level fields

Primary target values

Robot pose arrays

MegaTag2 pose arrays

Pose helper methods

Target arrays

Hardware and diagnostic fields

LimelightTarget_Fiducial fields

LimelightTarget_Barcode fields

Code example