Configuration methods

Pipeline control

`setPipelineIndex`

Switches the active pipeline to the specified index (0–9).

LimelightHelpers.setPipelineIndex("limelight", 2);

limelightName

string

required

Name of the Limelight NetworkTables table.

pipelineIndex

int

required

Pipeline index to activate. Valid range: 0–9.

`setPriorityTagID`

Sets the priority AprilTag ID. When a priority ID is set, the Limelight will prefer that tag when multiple are visible.

LimelightHelpers.setPriorityTagID("limelight", 7);

limelightName

string

required

Name of the Limelight NetworkTables table.

int

required

The AprilTag ID to prioritize.

`SetFiducialIDFiltersOverride`

Overrides the set of AprilTag IDs used for robot localization. Tags whose IDs are not in this list will be ignored for pose estimation.

// Only use tags 1, 2, and 7 for localization
LimelightHelpers.SetFiducialIDFiltersOverride("limelight", new int[]{1, 2, 7});

limelightName

string

required

Name of the Limelight NetworkTables table.

validIDs

int[]

required

Array of AprilTag IDs to permit for localization.

`SetFiducialDownscalingOverride`

Overrides the downscaling factor applied to the image before AprilTag detection. Higher downscale improves detection speed but may reduce maximum detection range.

LimelightHelpers.SetFiducialDownscalingOverride("limelight", 2.0f);

limelightName

string

required

Name of the Limelight NetworkTables table.

downscale

float

required

Downscale factor. Valid values: 0 (use pipeline setting), 1.0, 1.5, 2.0, 3.0, 4.0.

`SetThrottle`

Sets the frame-processing throttle. The camera processes one frame after skipping the specified number. Set to a value between 100–200 while the robot is disabled to reduce thermal output.

// Process every frame (default)
LimelightHelpers.SetThrottle("limelight", 0);

// Reduce heat when disabled
LimelightHelpers.SetThrottle("limelight", 150);

limelightName

string

required

Name of the Limelight NetworkTables table.

throttle

int

required

Number of frames to skip between processed frames. 0 = no throttle (process every frame).

LED control

`setLEDMode_PipelineControl`

Sets LED behavior to be controlled by the active pipeline configuration (ledMode = 0).

LimelightHelpers.setLEDMode_PipelineControl("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

`setLEDMode_ForceOff`

Forces the LEDs off regardless of the pipeline setting (ledMode = 1).

LimelightHelpers.setLEDMode_ForceOff("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

`setLEDMode_ForceBlink`

Forces the LEDs to blink continuously (ledMode = 2).

LimelightHelpers.setLEDMode_ForceBlink("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

`setLEDMode_ForceOn`

Forces the LEDs fully on regardless of the pipeline setting (ledMode = 3).

LimelightHelpers.setLEDMode_ForceOn("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

Stream mode

`setStreamMode_Standard`

Enables the standard side-by-side stream (stream = 0). The primary and secondary camera views appear side by side.

LimelightHelpers.setStreamMode_Standard("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

`setStreamMode_PiPMain`

Enables Picture-in-Picture mode with the secondary stream displayed in the corner of the primary stream (stream = 1).

LimelightHelpers.setStreamMode_PiPMain("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

`setStreamMode_PiPSecondary`

Enables Picture-in-Picture mode with the primary stream displayed in the corner of the secondary stream (stream = 2).

LimelightHelpers.setStreamMode_PiPSecondary("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

Camera geometry

`setCameraPose_RobotSpace`

Sets the camera’s mount position and orientation relative to the robot’s center. All translations are in meters; all angles are in degrees.

// Camera mounted 0.3 m forward, centered, 0.2 m up, tilted 30° down
LimelightHelpers.setCameraPose_RobotSpace("limelight",
    0.3,   // forward (m)
    0.0,   // side (m)
    0.2,   // up (m)
    0.0,   // roll (deg)
    -30.0, // pitch (deg)
    0.0    // yaw (deg)
);

limelightName

string

required

Name of the Limelight NetworkTables table.

forward

double

required

Forward offset from the robot center in meters.

side

double

required

Side (lateral) offset from the robot center in meters. Positive is to the left.

double

required

Vertical offset from the robot center in meters.

roll

double

required

Camera roll in degrees.

pitch

double

required

Camera pitch in degrees. Negative values tilt the camera downward.

yaw

double

required

Camera yaw in degrees relative to the robot’s forward direction.

`setCropWindow`

Sets the active crop window for the camera image. The crop window in the Limelight UI must be fully open (no UI crop applied) for this to take effect. Values are normalized: −1.0 is the left/bottom edge, 1.0 is the right/top edge.

// Crop to the center-left quarter of the image
LimelightHelpers.setCropWindow("limelight", -1.0, 0.0, -1.0, 1.0);

limelightName

string

required

Name of the Limelight NetworkTables table.

cropXMin

double

required

Left edge of the crop window. Range: −1.0 to 1.0.

cropXMax

double

required

Right edge of the crop window. Range: −1.0 to 1.0.

cropYMin

double

required

Bottom edge of the crop window. Range: −1.0 to 1.0.

cropYMax

double

required

Top edge of the crop window. Range: −1.0 to 1.0.

`setKeystone`

Applies horizontal and vertical keystone correction to the camera image.

LimelightHelpers.setKeystone("limelight", 0.1, -0.05);

limelightName

string

required

Name of the Limelight NetworkTables table.

horizontal

double

required

Horizontal keystone correction value. Range: −0.95 to 0.95.

vertical

double

required

Vertical keystone correction value. Range: −0.95 to 0.95.

`setFiducial3DOffset`

Sets a 3D offset point applied to the fiducial targeting solution, enabling easy targeting of a specific point relative to an AprilTag.

// Target a point 0.5 m above the AprilTag
LimelightHelpers.setFiducial3DOffset("limelight", 0.0, 0.0, 0.5);

limelightName

string

required

Name of the Limelight NetworkTables table.

offsetX

double

required

X offset in meters relative to the fiducial.

offsetY

double

required

Y offset in meters relative to the fiducial.

offsetZ

double

required

Z offset in meters relative to the fiducial.

MegaTag2 orientation

`SetRobotOrientation`

Sends the robot’s current orientation to the Limelight for use by the MegaTag2 localization algorithm. Only yaw is used by MegaTag2; set all rate and attitude parameters to 0. Internally calls Flush() to ensure the value reaches the camera before the next pose read.

// Called each loop iteration before getBotPoseEstimate_wpiBlue_MegaTag2
LimelightHelpers.SetRobotOrientation("limelight",
    gyro.getYaw(), // yaw (deg) — required
    0,             // yawRate — set 0
    0,             // pitch — set 0
    0,             // pitchRate — set 0
    0,             // roll — set 0
    0              // rollRate — set 0
);

limelightName

string

required

Name of the Limelight NetworkTables table.

yaw

double

required

Robot yaw in degrees. 0° = robot facing the Red Alliance wall in the standard FRC field orientation.

yawRate

double

required

Angular velocity of yaw in degrees per second. Set to 0 — not currently used by MegaTag2.

pitch

double

required

Robot pitch in degrees. Set to 0 — not currently used by MegaTag2.

pitchRate

double

required

Angular velocity of pitch in degrees per second. Set to 0.

roll

double

required

Robot roll in degrees. Set to 0 — not currently used by MegaTag2.

rollRate

double

required

Angular velocity of roll in degrees per second. Set to 0.

`SetRobotOrientation_NoFlush`

Identical to SetRobotOrientation but skips the internal Flush() call. Use this when you are batching multiple NT writes and want to flush manually, or when calling from a high-frequency loop where the extra flush overhead is undesirable.

LimelightHelpers.SetRobotOrientation_NoFlush("limelight",
    gyro.getYaw(), 0, 0, 0, 0, 0);
// ... other NT writes ...
LimelightHelpers.Flush();

limelightName

string

required

Name of the Limelight NetworkTables table.

yaw

double

required

Robot yaw in degrees.

yawRate

double

required

Angular velocity of yaw. Set to 0.

pitch

double

required

Robot pitch. Set to 0.

pitchRate

double

required

Angular velocity of pitch. Set to 0.

roll

double

required

Robot roll. Set to 0.

rollRate

double

required

Angular velocity of roll. Set to 0.

`SetIMUMode`

Configures the IMU mode used by the MegaTag2 localization algorithm.

LimelightHelpers.SetIMUMode("limelight", 1);

limelightName

string

required

Name of the Limelight NetworkTables table.

mode

int

required

IMU mode integer. Mode 0 = external IMU only (use SetRobotOrientation to provide heading). Higher modes enable Limelight’s internal IMU. See the MegaTag2 guide for usage guidance.

`SetIMUAssistAlpha`

Sets the complementary filter alpha for IMU Assist Modes 3 and 4. A higher alpha causes the internal IMU to converge onto the assist source more rapidly.

// Use default value
LimelightHelpers.SetIMUAssistAlpha("limelight", 0.001);

limelightName

string

required

Name of the Limelight NetworkTables table.

alpha

double

required

Complementary filter alpha. Default is 0.001. Higher values increase convergence speed.

Python scripting

`setPythonScriptData`

Sends an array of doubles to the currently running Python script on the Limelight.

double[] outData = {1.0, 2.5, 0.0};
LimelightHelpers.setPythonScriptData("limelight", outData);

limelightName

string

required

Name of the Limelight NetworkTables table.

outgoingPythonData

double[]

required

Array of doubles to pass to the Python script via the llrobot NetworkTables key.

`getPythonScriptData`

Returns the output array published by the currently running Python script on the Limelight.

double[] pythonOut = LimelightHelpers.getPythonScriptData("limelight");

limelightName

string

required

Name of the Limelight NetworkTables table.

returns

double[]

Array of doubles published by the Python script via the llpython NetworkTables key.

Data Classes

Methods

Pipeline control

`setPipelineIndex`

`setPriorityTagID`

`SetFiducialIDFiltersOverride`

`SetFiducialDownscalingOverride`

`SetThrottle`

LED control

`setLEDMode_PipelineControl`

`setLEDMode_ForceOff`

`setLEDMode_ForceBlink`

`setLEDMode_ForceOn`

Stream mode

`setStreamMode_Standard`

`setStreamMode_PiPMain`

`setStreamMode_PiPSecondary`

Camera geometry

`setCameraPose_RobotSpace`

`setCropWindow`

`setKeystone`

`setFiducial3DOffset`

MegaTag2 orientation

`SetRobotOrientation`

`SetRobotOrientation_NoFlush`

`SetIMUMode`

`SetIMUAssistAlpha`

Python scripting

`setPythonScriptData`

`getPythonScriptData`

Build docs developers (and LLMs) love

Data Classes

Methods

​Pipeline control

​setPipelineIndex

​setPriorityTagID

​SetFiducialIDFiltersOverride

​SetFiducialDownscalingOverride

​SetThrottle

​LED control

​setLEDMode_PipelineControl

​setLEDMode_ForceOff

​setLEDMode_ForceBlink

​setLEDMode_ForceOn

​Stream mode

​setStreamMode_Standard

​setStreamMode_PiPMain

​setStreamMode_PiPSecondary

​Camera geometry

​setCameraPose_RobotSpace

​setCropWindow

​setKeystone

​setFiducial3DOffset

​MegaTag2 orientation

​SetRobotOrientation

​SetRobotOrientation_NoFlush

​SetIMUMode

​SetIMUAssistAlpha

​Python scripting

​setPythonScriptData

​getPythonScriptData

Build docs developers (and LLMs) love

Pipeline control

`setPipelineIndex`

`setPriorityTagID`

`SetFiducialIDFiltersOverride`

`SetFiducialDownscalingOverride`

`SetThrottle`

LED control

`setLEDMode_PipelineControl`

`setLEDMode_ForceOff`

`setLEDMode_ForceBlink`

`setLEDMode_ForceOn`

Stream mode

`setStreamMode_Standard`

`setStreamMode_PiPMain`

`setStreamMode_PiPSecondary`

Camera geometry

`setCameraPose_RobotSpace`

`setCropWindow`

`setKeystone`

`setFiducial3DOffset`

MegaTag2 orientation

`SetRobotOrientation`

`SetRobotOrientation_NoFlush`

`SetIMUMode`

`SetIMUAssistAlpha`

Python scripting

`setPythonScriptData`

`getPythonScriptData`