Data Sheet

October 2017 BNO080 Datasheet 1000-3927

yaw due to the characteristics of gyroscopes, but this is seen as preferable for this output versus a corrected

output.

2.2.3 AR/VR Stabilized Game Rotation vector

While the magnetometer is removed from the calculation of the game rotation vector, the accelerometer itself can

create a potential correction in the rotation vector produced (i.e. the estimate of gravity changes). For applications

(typically augmented or virtual reality applications) where a sudden jump can be disturbing, the output is adjusted

to prevent these jumps in a manner that takes account of the velocity of the sensor system. This process is called

AR/VR stabilization. An FRS (Flash Record System – see Figure 1-31) record is provided to allow configuration of

this feature.

2.2.4 Rotation Vector

The rotation vector provides an orientation output that is expressed as a quaternion referenced to magnetic north

and gravity. It is produced by fusing the outputs of the accelerometer, gyroscope and magnetometer. The rotation

vector is the most accurate orientation estimate available. The magnetometer provides correction in yaw to

reduce drift and the gyroscope enables the most responsive performance.

2.2.5 AR/VR Stabilized Rotation Vector

Estimates of the magnetic field and the roll/pitch of the device can create a potential correction in the rotation

vector produced. For applications (typically augmented or virtual reality applications) where a sudden jump can be

disturbing, the output is adjusted to prevent these jumps in a manner that takes account of the velocity of the

sensor system. This process is called AR/VR stabilization. An FRS (Flash Record System – see Figure 1-31)

record is provided to allow configuration of this feature.

2.2.6 Gyro rotation Vector

Head tracking systems within a virtual reality headset require low latency processing of motion. To facilitate this,

the BNO080 can provide a rotation vector at rates up to 1kHz. The gyro rotation Vector provides an alternate

orientation to the standard rotation vector. Compared to the standard rotation vector the gyro rotation vector has

an optimized processing path and correction style (correction is the adjustments made to the output based on

more accurate estimates of gravity, mag field, angular velocity) that is suitable for head tracking applications.

By default the Gyro rotation vector provides an orientation output that is expressed as a quaternion. It can be

configured via FRS record to be based on either the rotation vector (using the magnetometer) or the game

rotation vector (ignoring the magnetometer).

2.2.7 Gyro rotation Vector Prediction

In virtual reality systems reducing latency is a vital requirement to proving an immersive experience. The gyro

rotation vector provides a low latency output. However in a system there are many factors that can add to the

latency budget:

• IMU processing

• Data path between IMU and video rendering

• Video rendering

• Video buffer/display write

To aid in the reduction of the overall system latency the BNO080 can derive an expected orientation for some

time in the future. Predicting 20-30 ms into the future can significantly improve the perception of reality within the

virtual reality world. The predictor accepts the gyro rotation vector as input and produces a second rotation vector

for some time in the future. An FRS record is used to tune the predictor for the type of motion. The predictor

accepts three constants (alpha, beta, gamma) for the tuning.

The default prediction time is 28ms and is determined for motion typical of a head tracker. Some typical

parameters that can be used are captured in Figure 2-2. These values are all for motion typical of a head tracker.