IMU Setup & Calibration

Inconsistent turns are almost always an IMU problem. This guide covers mounting, PROS API, EZ Template integration, drift, and a complete troubleshooting table for the four failure modes you'll actually encounter.

The V5 Inertial Sensor (IMU) is a gyroscope + accelerometer. For drivetrains, you only care about the gyroscope — it measures rotation rate and integrates it into a heading angle (degrees). EZ Template uses this heading to:

• Hold straight lines: The heading PID constantly corrects drive direction using the IMU. Without it, your robot drifts
• Execute precise turns: pid_turn_set(90, 90) is targeting an IMU heading of 90°, not a timer
• Accumulate absolute position: Odometry tracks heading changes — IMU accuracy compounds across the whole auton

• Mount flat: The IMU reads rotation around its Z-axis. If it's tilted even 5°, every turn reading is wrong
• Mount at robot center (or close): Off-center mounting still works, but reduces accuracy on tight turns
• Away from motors: Motor vibration introduces noise. Keep at least 3 inches of physical separation
• Away from the Brain: The Brain's Bluetooth module can cause EMI interference with the IMU
• Rigid mount only: If the IMU can flex or vibrate independently, its readings will be noisy. Bolt it, don't zip-tie it

// Declare in globals.hpp
pros::Imu imu(7); // port number

// In initialize() — ALWAYS call before using
imu.reset(); // starts calibration, takes ~2 seconds
while(imu.is_calibrating()) pros::delay(10); // wait for finish

// Read heading (0–360, clockwise positive in EZ Template)
double heading = imu.get_rotation(); // accumulates past 360
double heading = imu.get_heading();  // wraps 0–360

// Reset to zero mid-auton
imu.set_rotation(0.0);

EZ Template handles the IMU automatically — you just declare it in the constructor. The 4th argument is the IMU port:

ez::Drive chassis ({-1,-2,-3}, {4,5,6}, 7, 3.25, 36.0/48.0, 360);
//                              ↑ IMU port — must match physical wiring

EZ Template's initialize() calls chassis.initialize() which resets the IMU automatically. You don't need manual imu.reset() calls in most setups.

• Place robot on competition field tile (not smooth floor — carpet surface matters)
• Do not touch robot after uploading code. Even a small bump during calibration corrupts the zero
• Wait for Brain display to confirm IMU is calibrated. EZ Template shows "Calibrating..." — do not proceed until it clears
• Run a test turn: pid_turn_set(90, 90); chassis.pid_wait(); — should stop within ±1° of 90°
• Run 5 turns in a row and check if error accumulates. Under 3° total drift across 5 turns = good calibration

All gyroscopes drift — the V5 IMU is no exception. In a 15-second auton, expect 0.5–2° of total drift if well-calibrated. This is acceptable. If drift exceeds 3° across the full auton:

• Check mounting rigidity. A flexing IMU mount is the #1 drift amplifier
• Add a mid-auton reset. After your first scoring action, call chassis.drive_imu_reset() and define subsequent turns from that new zero
• Consider odometry. If your game requires very precise multi-point routing, an odom system with tracking wheels compensates for IMU drift automatically. See the odometry guide