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/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdint.h>
#include <math.h>
#include <sys/types.h>
#include <utils/Errors.h>
#include <hardware/sensors.h>
#include "LegacyRotationVectorSensor.h"
namespace android {
// ---------------------------------------------------------------------------
template <typename T>
static inline T clamp(T v) {
return v < 0 ? 0 : v;
}
LegacyRotationVectorSensor::LegacyRotationVectorSensor()
: mSensorDevice(SensorDevice::getInstance()),
mSensorFusion(SensorFusion::getInstance()),
mALowPass(M_SQRT1_2, 1.5f),
mAX(mALowPass), mAY(mALowPass), mAZ(mALowPass),
mMLowPass(M_SQRT1_2, 1.5f),
mMX(mMLowPass), mMY(mMLowPass), mMZ(mMLowPass)
{
}
bool LegacyRotationVectorSensor::process(sensors_event_t* outEvent,
const sensors_event_t& event)
{
const static double NS2S = 1.0 / 1000000000.0;
if (event.type == SENSOR_TYPE_MAGNETIC_FIELD) {
const double now = event.timestamp * NS2S;
if (mMagTime == 0) {
mMagData[0] = mMX.init(event.magnetic.x);
mMagData[1] = mMY.init(event.magnetic.y);
mMagData[2] = mMZ.init(event.magnetic.z);
} else {
double dT = now - mMagTime;
mMLowPass.setSamplingPeriod(dT);
mMagData[0] = mMX(event.magnetic.x);
mMagData[1] = mMY(event.magnetic.y);
mMagData[2] = mMZ(event.magnetic.z);
}
mMagTime = now;
}
if (event.type == SENSOR_TYPE_ACCELEROMETER) {
const double now = event.timestamp * NS2S;
float Ax, Ay, Az;
if (mAccTime == 0) {
Ax = mAX.init(event.acceleration.x);
Ay = mAY.init(event.acceleration.y);
Az = mAZ.init(event.acceleration.z);
} else {
double dT = now - mAccTime;
mALowPass.setSamplingPeriod(dT);
Ax = mAX(event.acceleration.x);
Ay = mAY(event.acceleration.y);
Az = mAZ(event.acceleration.z);
}
mAccTime = now;
const float Ex = mMagData[0];
const float Ey = mMagData[1];
const float Ez = mMagData[2];
float Hx = Ey*Az - Ez*Ay;
float Hy = Ez*Ax - Ex*Az;
float Hz = Ex*Ay - Ey*Ax;
const float normH = sqrtf(Hx*Hx + Hy*Hy + Hz*Hz);
if (normH < 0.1f) {
// device is close to free fall (or in space?), or close to
// magnetic north pole. Typical values are > 100.
return false;
}
const float invH = 1.0f / normH;
const float invA = 1.0f / sqrtf(Ax*Ax + Ay*Ay + Az*Az);
Hx *= invH;
Hy *= invH;
Hz *= invH;
Ax *= invA;
Ay *= invA;
Az *= invA;
const float Mx = Ay*Hz - Az*Hy;
const float My = Az*Hx - Ax*Hz;
const float Mz = Ax*Hy - Ay*Hx;
// matrix to rotation vector (normalized quaternion)
float qw = sqrtf( clamp( Hx + My + Az + 1) * 0.25f );
float qx = sqrtf( clamp( Hx - My - Az + 1) * 0.25f );
float qy = sqrtf( clamp(-Hx + My - Az + 1) * 0.25f );
float qz = sqrtf( clamp(-Hx - My + Az + 1) * 0.25f );
qx = copysignf(qx, Ay - Mz);
qy = copysignf(qy, Hz - Ax);
qz = copysignf(qz, Mx - Hy);
// this quaternion is guaranteed to be normalized, by construction
// of the rotation matrix.
*outEvent = event;
outEvent->data[0] = qx;
outEvent->data[1] = qy;
outEvent->data[2] = qz;
outEvent->data[3] = qw;
outEvent->sensor = '_rov';
outEvent->type = SENSOR_TYPE_ROTATION_VECTOR;
return true;
}
return false;
}
status_t LegacyRotationVectorSensor::activate(void* ident, bool enabled) {
if (enabled) {
mMagTime = 0;
mAccTime = 0;
}
return mSensorFusion.activate(this, enabled);
}
status_t LegacyRotationVectorSensor::setDelay(void* ident, int handle, int64_t ns) {
return mSensorFusion.setDelay(this, ns);
}
Sensor LegacyRotationVectorSensor::getSensor() const {
sensor_t hwSensor;
hwSensor.name = "Rotation Vector Sensor";
hwSensor.vendor = "Google Inc.";
hwSensor.version = 3;
hwSensor.handle = '_rov';
hwSensor.type = SENSOR_TYPE_ROTATION_VECTOR;
hwSensor.maxRange = 1;
hwSensor.resolution = 1.0f / (1<<24);
hwSensor.power = mSensorFusion.getPowerUsage();
hwSensor.minDelay = mSensorFusion.getMinDelay();
Sensor sensor(&hwSensor);
return sensor;
}
// ---------------------------------------------------------------------------
}; // namespace android
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