GravitySensor.cpp revision 984826cc158193e61e3a00359ef4f6699c7d748a 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <stdint.h>
18#include <math.h>
19#include <sys/types.h>
20
21#include <utils/Errors.h>
22
23#include <hardware/sensors.h>
24
25#include "GravitySensor.h"
26#include "SensorDevice.h"
27#include "SensorFusion.h"
28
29namespace android {
30// ---------------------------------------------------------------------------
31
32GravitySensor::GravitySensor(sensor_t const* list, size_t count)
33    : mSensorDevice(SensorDevice::getInstance()),
34      mSensorFusion(SensorFusion::getInstance()),
35      mAccTime(0),
36      mLowPass(M_SQRT1_2, 1.5f),
37      mX(mLowPass), mY(mLowPass), mZ(mLowPass)
38{
39    for (size_t i=0 ; i<count ; i++) {
40        if (list[i].type == SENSOR_TYPE_ACCELEROMETER) {
41            mAccelerometer = Sensor(list + i);
42            break;
43        }
44    }
45}
46
47bool GravitySensor::process(sensors_event_t* outEvent,
48        const sensors_event_t& event)
49{
50    const static double NS2S = 1.0 / 1000000000.0;
51    if (event.type == SENSOR_TYPE_ACCELEROMETER) {
52        vec3_t g;
53        if (mSensorFusion.hasGyro()) {
54            if (!mSensorFusion.hasEstimate())
55                return false;
56            const mat33_t R(mSensorFusion.getRotationMatrix());
57            // FIXME: we need to estimate the length of gravity because
58            // the accelerometer may have a small scaling error. This
59            // translates to an offset in the linear-acceleration sensor.
60            g = R[2] * GRAVITY_EARTH;
61        } else {
62            const double now = event.timestamp * NS2S;
63            if (mAccTime == 0) {
64                g.x = mX.init(event.acceleration.x);
65                g.y = mY.init(event.acceleration.y);
66                g.z = mZ.init(event.acceleration.z);
67            } else {
68                double dT = now - mAccTime;
69                mLowPass.setSamplingPeriod(dT);
70                g.x = mX(event.acceleration.x);
71                g.y = mY(event.acceleration.y);
72                g.z = mZ(event.acceleration.z);
73            }
74            g *= (GRAVITY_EARTH / length(g));
75            mAccTime = now;
76        }
77        *outEvent = event;
78        outEvent->data[0] = g.x;
79        outEvent->data[1] = g.y;
80        outEvent->data[2] = g.z;
81        outEvent->sensor = '_grv';
82        outEvent->type = SENSOR_TYPE_GRAVITY;
83        return true;
84    }
85    return false;
86}
87
88status_t GravitySensor::activate(void* ident, bool enabled) {
89    status_t err;
90    if (mSensorFusion.hasGyro()) {
91        err = mSensorFusion.activate(this, enabled);
92    } else {
93        err = mSensorDevice.activate(this, mAccelerometer.getHandle(), enabled);
94        if (err == NO_ERROR) {
95            if (enabled) {
96                mAccTime = 0;
97            }
98        }
99    }
100    return err;
101}
102
103status_t GravitySensor::setDelay(void* ident, int handle, int64_t ns)
104{
105    if (mSensorFusion.hasGyro()) {
106        return mSensorFusion.setDelay(this, ns);
107    } else {
108        return mSensorDevice.setDelay(this, mAccelerometer.getHandle(), ns);
109    }
110}
111
112Sensor GravitySensor::getSensor() const {
113    sensor_t hwSensor;
114    hwSensor.name       = "Gravity Sensor";
115    hwSensor.vendor     = "Google Inc.";
116    hwSensor.version    = mSensorFusion.hasGyro() ? 3 : 2;
117    hwSensor.handle     = '_grv';
118    hwSensor.type       = SENSOR_TYPE_GRAVITY;
119    hwSensor.maxRange   = GRAVITY_EARTH * 2;
120    hwSensor.resolution = mAccelerometer.getResolution();
121    hwSensor.power      = mSensorFusion.hasGyro() ?
122            mSensorFusion.getPowerUsage() : mAccelerometer.getPowerUsage();
123    hwSensor.minDelay   = mSensorFusion.hasGyro() ?
124            mSensorFusion.getMinDelay() : mAccelerometer.getMinDelay();
125    Sensor sensor(&hwSensor);
126    return sensor;
127}
128
129// ---------------------------------------------------------------------------
130}; // namespace android
131
132