nn::hid::CTR::GyroscopeReader Class

class GyroscopeReader : private ADLFireWall::NonCopyable

Class for loading sampling data from the gyro sensor.

Sampling Rate

Samples the angular velocity of the gyro sensor an average of every 10 milliseconds. Use the nn::hid::CTR::Gyroscope class to know when sampling occurs, allowing you to accurately monitor sampling timing.

Output Value Details

This class stores sampling results as a nn::hid::CTR::GyroscopeStatus structure. This structure contains not just the angular velocity, but also information about the attitude calculated from the angular velocity. Attitude is calculated when the nn::hid::CTR::GyroscopeReader::Read or nn::hid::CTR::GyroscopeReader::ReadLatest functions are called, and either one must be called regularly (ideally every frame). Data stored in the internal buffer can become discontinuous, resulting in less accurate attitude information, if too much time elapses between calls to either of these functions.

Conditions to Start Sampling

Gyro sensor sampling halts in two cases: when the system is in Sleep Mode, and when there are no instances of the GyroscopeReader class. You must destroy all instances to explicitly stop sampling.
It takes up to approximately 160 milliseconds for the system to transition to a state where sampling is possible. No sampling is done during this transition time, and calls to the nn::hid::CTR::GyroscopeReader::Read or nn::hid::CTR::GyroscopeReader::ReadLatest functions have no effect. To be sure to obtain sampling results, Nintendo recommends calling the nn::hid::CTR::HidBase::WaitSampling function in the nn::hid::CTR::Gyroscope class, which waits until results have been sampled at least once. Starting from the second instance, this sampling wait time is the same as the wait until the next sample, which is a maximum of approximately 10 milliseconds.

Correction Processing

This class includes the following correction processing for getting information more accurately.

Acceleration Correction	Uses the accelerometer to improve the accuracy of CTR attitude calculations.
Zero-Point Drift Correction	The gyro sensor's zero point can drift due to environmental factors. This correction automatically detects zero-point drift and adjusts angular velocity values accordingly.

All correction processes are enabled by default, but can be configured or disabled as necessary. For details, see the various function references.

Output Value Processing Features

This class includes the following features to process output values.

Zero-Point Play Tolerance	When the sampling results are within any radius centered on the zero-point, that is output as the zero-point. This is used when, for example, you don't want to reflect small movements in the output.
Axial Rotation	The sampling results are multiplied by any rotational matrix and then output. You can get output that reflects placement of the gyro sensor at an angle.

All processing features are disabled by default. Configure and enable them as needed. For details, see the various function references.

Axis Orientation

The default gyro sensor axes are as follows.

X+	A clockwise rotation about the direction indicated by the Left Button on the +Control Pad.
Y+	A clockwise rotation about the direction normal to and outward from the Touch Screen.
Z+	A clockwise rotation about the direction indicated by the Up Button on the +Control Pad.

Recalibration of Accelerometer from HOME Menu

A future update to the HOME menu will add a feature enabling users to recalibrate the accelerometer whenever they like.

As a result, correction in accordance with the user's environment may start while the user is transitioned from the application to the HOME Menu using the HOME Button.
After this operation, the values retrieved from the nn::hid::CTR::GyroscopeReader::Read and nn::hid::CTR::GyroscopeReader::ReadLatest functions will be the corrected values. In most cases, the corrected values will accurately reflect the user's environment.

The applications, however, need not take any special measures to deal with this.

Miscellaneous Notes

This class maintains an internal instance of the nn::hid::CTR::AccelerometerReader class for acceleration correction. The accelerometer is started when an instance is generated.

ADLFireWall::NonCopyable
  nn::hid::CTR::GyroscopeReader

2011/03/15

Explained the possibility of accelerometer recalibration from the HOME Menu.

2010/12/06

Added explanation of conditions under which sampling stops.

2010/10/20

Initial version.