IMU Setup & Calibration

flowchart TD
    Start([New bot, IMU mounted]) --> Mount[Verify mounting:
flat surface, secured
not over a motor]
    Mount --> Init[In initialize:
chassis.drive_imu_calibrate true
blocks ~3 seconds]
    Init --> Idle[Don't move robot
during calibration
'IMU calibrating' message on LCD]
    Idle --> Test[Test: turn robot 90 degrees
read chassis.drive_imu_get]
    Test --> Q1{Reading close
to 90?}
    Q1 -->|"Yes, within ±2°"| Done([IMU good to use])
    Q1 -->|"No, way off"| Q2{Drift over time?}
    Q2 -->|"Yes, slowly drifts"| Drift[Normal — IMU drift is real
reset between auton steps
chassis.drive_imu_reset]
    Q2 -->|"No, instantly wrong"| Mount2[Mounting issue
recalibrate flat]
    Mount2 --> Init

    style Start fill:#1e293b,stroke:#22d3ee,stroke-width:2px,color:#e2e8f0
    style Done fill:#1e293b,stroke:#22c55e,stroke-width:2px,color:#e2e8f0
    style Q1 fill:#fbbf24,color:#0f172a,stroke:#fbbf24
    style Q2 fill:#fbbf24,color:#0f172a,stroke:#fbbf24

Your autonomous turns are only as accurate as your IMU. A miscalibrated or misread IMU drifts 5–10° per turn — that compounds across a 15-second auton into a robot that misses its target by a foot.

The V5 IMU (Inertial Measurement Unit) tracks the robot's heading in degrees. EZ Template uses it to execute turns like pid_turn_set(90, 90) accurately. Without it, turns rely on encoder ticks alone — which drift under any wheel slip, carpet variation, or battery difference.

• Mount flat — the IMU must be parallel to the ground. Even a 5° tilt causes constant heading error.
• Away from motors — motors generate magnetic interference. At least 3 inches of clearance from any motor.
• Away from high-current wires — power cables near the IMU corrupt readings. Route them separately.
• Rigid mounting — the IMU must not flex or vibrate relative to the robot frame. A loose IMU drifts constantly.
• Center of the robot is ideal — it minimizes rotational effects from acceleration at the edges.

// In include/globals.hpp — the 5th parameter is the IMU port
ez::Drive chassis ({-1, -2, -3},   // left motors
                   {4, 5, 6},      // right motors
                   7,              // ← IMU port number here
                   3.25, 0.75, 360);

// EZ Template handles calibration automatically in initialize():
// ez::as::initialize() triggers IMU calibration.
// Do NOT touch the robot until Brain shows "Calibrated"

// Reset heading to 0 at any point in auton (useful after wall alignment)
chassis.drive_imu_reset();

// Set heading to a specific value (e.g. after aligning to wall)
chassis.drive_imu_set(90.0);

// Read current heading (for debugging)
float heading = chassis.drive_imu_get();

• Robot is placed on the field, not moving, before you plug in the Brain cable to upload.
• After upload completes, wait for the Brain screen to show your auton selector — this means calibration finished.
• Do not move the robot during the first 3 seconds after powering on (calibration runs on startup).
• Check the Brain port screen — IMU should show a green heading value, not "?".
• Run a quick 90° turn test before queuing. If it overshoots or undershoots, your mount shifted.