Swerve Calibration

Three operations in the swerve code all get called resetting or seeding. Mix them up and you get a robot that drives beautifully and has no idea where it is.

seedFieldCentric(), on the left bumper, changes which way the sticks call forward: whatever the robot faces now becomes forward. Every loop, applyOperatorPerspective() sets that same forward from alliance color: 0° on blue and 180° on red. Neither supplies an x or a y.

resetPose(Pose2d) moves the pose itself: x, y and heading in meters from the blue corner. It exists on the Phoenix 6 drivetrain, but DriveMechanism does not expose it and nothing calls it. Until Vision in Workshop 6, read Drivetrain/Pose as distance traveled since boot.

Each module has a CANcoder reading which way its wheel points, and an offset saying which reading counts as straight ahead. The four k*EncoderOffset constants in your file came from the wheels you held straight by eye in the generator. A straight edge does better.

1. Disable the robot. Nothing should be commanding a module while you set it.
2. Press a straight edge flat along one side so both wheels on that side sit against it, then do the other side. By eye is not close enough: half a degree of steering error walks the robot 5 cm sideways over six meters.
3. Check which way each module faces. CTRE marks this one important: every module's bevel gear has to face the vertical center of the robot. A module that is straight but flipped zeroes 180° off, and the drive verification tests fail later without saying why.
4. Holding the wheels straight, run the calibration step in the Tuner X swerve generator. It reads all four CANcoders where they sit and writes the offset constants for you.

A steering motor holds an angle. That is a position loop with no gravity to fight, so skip kG and start at kS. The generator gave you real numbers, kP 100, kD 0.5, kS 0.1 and kV 1.91, and they are often close. Adjust them rather than starting from zero.

Follow the order from the PID page. kS is the smallest output that breaks the module loose. Raise kP until it oscillates, then back off. Add kD, as much as you can get without jitter. Change one number per test.

DriveMechanism publishes Drivetrain/ModuleStates and Drivetrain/ModuleTargets. Put the angle from both on one AdvantageScope plot and flick the right stick. Tuned looks like two traces on top of each other. Untuned lags, overshoots, or buzzes.

Put the robot on the floor with a carpet seam or a taped line ahead of it, and keep a hand on disable.

1. Enable, push the left stick forward, and sight along the line for a few meters.
2. Flick the right stick back and forth while you watch the angle plot.
3. Turn 90° in place and press the left bumper. Watch Drivetrain/Pose.

A consistent curve to one side means a module is zeroed wrong, so put the straight edge back on and re-save. A wander that comes and goes is the steer gains. With both clean, go on to Swerve Drive Tuning for the measurements that need the carpet.