AprilTagAuto

01ROBOT SETUP: Configure directions, BRAKE behavior, encoder mode, and zero motor power before anything can move.

02START THE LIMELIGHT: Pipeline 0 detects AprilTags. A fast poll rate gives the control loops frequent steering updates.

03INIT DISPLAY: Scan continuously before START. Show R1-R8 and the triangulated red-center distance while all motor powers remain zero.

04WAIT FOR START: Autonomous movement is blocked until the Driver Station START button is pressed.

05ACQUIRE MEANS FIND AND CHOOSE

For up to 3 seconds, scan for enough information to build a center: at least one visible tag from each half of an alliance. The program may see many tags, but it chooses the nearer complete red or blue center. The timeout prevents an endless loop when no usable target exists.

06CENTER USING A HORIZONTAL ANGLE

currentTx means the target’s horizontal X angle in degrees; Tx here does not mean transmit. Positive and negative tell which way to turn. Within 2 degrees counts as centered. Requiring 5 centered camera frames filters flicker: one lucky noisy reading cannot end the turn early.

07DRIVE TO A 24-INCH RANGE

Range means straight-line distance from camera to calculated center. The robot drives while currentRange is greater than 24 inches and stops at 24 or less. Small unequal left/right powers correct the horizontal angle while moving. The 8-second timeout and found flag stop the robot if vision fails.

08FINAL SAFETY STOP: Set every motor to zero and stop the Limelight when autonomous finishes.

09FRESH FRAME, FRESH FLAGS

Every camera frame is a new measurement. Reset found and visible flags before reading it. Otherwise a tag that disappeared could leave an old true value behind, making the robot steer using stale information.

10WHAT THE LIMELIGHT RETURNS

getLatestResult retrieves the newest processed image result. Fiducial means a known visual marker. FiducialResults is a list of all recognized AprilTags, and the for-each loop performs the same geometry on each list item.

11CAMERA COORDINATES AND POSE

Pose means position plus rotation. X is left/right, Y is up/down, and Z is forward from the camera. Yaw is left/right rotation; pitch is up/down tilt. All are needed because the tag strip may be viewed from an angle.

12SIGNED X, Y, Z VALUES

A signed number contains direction and size. For example, negative X may mean left and positive X right. Squaring removes the signs for distance, but keeping signs before that is essential for steering and projecting hidden points.

13DEGREES AND ROTATION

Yaw is like turning your head left/right; pitch is like nodding up/down. The Limelight gives degrees. The Blocks sine and cosine operations convert these degree angles internally, so students do not need to calculate radians.

14WHY SQUARE, ADD, THEN SQUARE ROOT?

Each axis is one side of a 3D right-angle path. Squaring makes every contribution positive. Adding X²+Y²+Z² combines all three dimensions. The square root returns the direct camera-to-tag distance. Multiply meters by 39.3701 for inches.

15WHY FOUR GROUP NUMBERS?

0 means red first half R1–R4; 1 means red second half R5–R8; 2 and 3 are the matching blue halves. One visible tag in group 0 plus one in group 1 can build the red center. Groups 2 and 3 build blue.

16BIOBUZZ TAG MAP AND OFFSETS

IDs 30–37 are red R1–R8; IDs 38–45 are blue B1–B8. Tag centers within each four-tag strip sit at -6.5, -2.75, +2.75, and +6.5 inches. Those known measurements let one visible tag estimate a hidden endpoint.

17ROTATE A KNOWN OFFSET WITH TRIGONOMETRY

An offset measured along the tag strip is not automatically camera-left/right when the strip is angled. Cosine gives the component along an axis; sine gives the perpendicular component. Using yaw and pitch rotates the offset into camera X, Y, and Z. Divide inches by 39.3701 first because pose coordinates are meters.

18MIDPOINT, DISTANCE, AND DIRECTION

Average endpoint coordinates to find the center: (A+B)/2 on each axis. Then distance=square root of X²+Y²+Z², the 3D Pythagorean theorem. atan2(X,Z) gives the signed left/right angle even when X or Z is zero; ordinary tangent division could fail or lose the correct quadrant.

19TARGET STATE VARIABLES

selectedId uses 0 for red center and 1 for blue center; it is not a physical tag ID. currentRange is center distance in inches. currentTx is center horizontal angle in degrees. found must be true before any vision-guided motor command is allowed.