BHI385 Smart IMU - Game Rotation Vector

This page covers reading orientation as a normalized quaternion from the BHI385's Game Rotation Vector virtual sensor.

---

Game Rotation Vector (quaternion)

The Game Rotation Vector fuses accelerometer and gyroscope data to output a normalized quaternion representing the device's orientation. Pitch and roll are absolute (gravity-referenced); yaw drifts over time because there is no magnetometer.

void setup()
{
    // ... begin() and loadFirmware() as above ...

    imu.enableGameRotationVector(100.0f); // 100 Hz
}

void loop()
{
    if (imu.update())
    {
        if (imu.quatUpdated())
        {
            Serial.print("X: "); Serial.print(imu.getQuatX(), 4);
            Serial.print("  Y: "); Serial.print(imu.getQuatY(), 4);
            Serial.print("  Z: "); Serial.print(imu.getQuatZ(), 4);
            Serial.print("  W: "); Serial.println(imu.getQuatW(), 4);
        }
        imu.clearUpdatedFlags();
    }
    delay(20);
}

Serial monitor Game Rotation Vector output

imu.enableGameRotationVector()

Enables the Game Rotation Vector virtual sensor, which fuses accelerometer and gyroscope data to produce a normalized quaternion (x, y, z, w). Does not use a magnetometer, so yaw is relative to the device orientation at power-on.

Returns value: true if the sensor was configured successfully

Function parameters:

Type	Name	Description
float	rateHz	Output data rate in Hz. Default: 100.0f

imu.getQuatX() / getQuatY() / getQuatZ() / getQuatW()

Returns the specified component of the most recently received normalized quaternion. All four components are in the range -1.0 to +1.0. Valid after update() returns with quatUpdated() true.

Returns value: Quaternion component as a float in range [-1, +1]