[Drivers] Add sensor framework

components/drivers/sensors/SConscript

+# SConscript for sensor framework 
+
+from building import *
+
+cwd = GetCurrentDir()
+src = Glob('*.c') + Glob('*.cpp') 
+CPPPATH = [cwd, cwd + '/../include']
+
+group = DefineGroup('Sensors', src, depend = ['RT_USING_SENSOR', 'RT_USING_DEVICE'], CPPPATH = CPPPATH)
+
+Return('group')
+

components/drivers/sensors/sensor.cpp

+#include <stddef.h>
+#include "sensor.h"
+
+/** 
+ * Sensor
+ */
+Sensor::Sensor()
+{
+	this->next = this->prev = NULL;
+	Subscribe(NULL, NULL);
+}
+
+Sensor::~Sensor()
+{
+}
+
+int Sensor::GetType(void)
+{
+    return this->type;
+}
+
+int Sensor::Subscribe(SensorEventHandler_t *handler, void* user_data)
+{
+    this->evtHandler = handler;
+    this->userData = user_data;
+
+    return 0;
+}
+
+int Sensor::Publish(sensors_event_t* event)
+{
+	if (this->evtHandler != NULL)
+	{
+		/* invoke subscribed handler */
+		(*evtHandler)(this, event, this->userData);
+	}
+
+    return 0;
+}
+
+/**
+ * Sensor Manager
+ */
+/* sensor manager instance */
+static SensorManager _sensor_manager;
+
+SensorManager::SensorManager()
+{
+	sensorList = NULL;
+}
+
+SensorManager::~SensorManager()
+{
+}
+
+int SensorManager::RegisterSensor(Sensor* sensor)
+{
+    SensorManager* self = &_sensor_manager;
+    
+    RT_ASSERT(sensor != RT_NULL);
+
+	/* add sensor into the list */
+	if (self->sensorList = NULL)
+	{
+		sensor->prev = sensor->next = sensor;
+	}
+	else
+	{
+		sensor->prev = self->sensorList;
+		sensor->next = self->sensorList->next;
+
+		self->sensorList->next->prev = sensor;
+		self->sensorList->next = sensor;
+	}
+
+	/* point the sensorList to this sensor */
+	self->sensorList = sensor;
+
+	return 0;
+}
+
+int SensorManager::DeregisterSensor(Sensor* sensor)
+{
+    SensorManager* self = &_sensor_manager;
+
+	/* disconnect sensor list */
+	sensor->next->prev = sensor->prev;
+	sensor->prev->next = sensor->next;
+
+	/* check the sensorList */
+	if (sensor == self->sensorList)
+	{
+		if (sensor->next == sensor) self->sensorList = NULL; /* empty list */
+		else self->sensorList = sensor->next;
+	}
+
+	/* re-initialize sensor node */
+	sensor->next = sensor->prev = sensor;
+
+    return 0;
+}
+
+Sensor *SensorManager::GetDefaultSensor(int type)
+{
+    SensorManager* self = &_sensor_manager;
+	Sensor *sensor = self->sensorList;
+
+	if (sensor == NULL) return NULL;
+
+	do
+	{
+		/* find the same type */
+		if (sensor->GetType() == type) return sensor;
+
+		sensor = sensor->next;
+	}
+	while (sensor != self->sensorList);
+
+    return NULL;
+}
+
+int SensorManager::Subscribe(int type, SensorEventHandler_t *handler, void* user_data)
+{
+	Sensor *sensor;
+
+	sensor = SensorManager::GetDefaultSensor(type);
+	if (sensor != NULL)
+	{
+		sensor->Subscribe(handler, user_data);
+		return 0;
+	}
+
+    return -1;
+}
+

components/drivers/sensors/sensor.h

+/*
+ * File      : sensors.h
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2014, RT-Thread Development Team
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rt-thread.org/license/LICENSE
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2014-08-03     Bernard      the first version
+ */
+
+/* Modified from: https://github.com/android/platform_hardware_libhardware/blob/master/include/hardware/sensors.h */
+
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#ifndef SENSORS_H__
+#define SENSORS_H__
+
+#include <rtdevice.h>
+
+#include <stdint.h>
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
+/**
+ * Handles must be higher than SENSORS_HANDLE_BASE and must be unique.
+ * A Handle identifies a given sensors. The handle is used to activate
+ * and/or deactivate sensors.
+ * In this version of the API there can only be 256 handles.
+ */
+#define SENSORS_HANDLE_BASE             0
+#define SENSORS_HANDLE_BITS             8
+#define SENSORS_HANDLE_COUNT            (1<<SENSORS_HANDLE_BITS)
+
+
+/*
+ * flags for (*batch)()
+ * Availability: SENSORS_DEVICE_API_VERSION_1_0
+ * see (*batch)() documentation for details
+ */
+enum {
+    SENSORS_BATCH_DRY_RUN               = 0x00000001,
+    SENSORS_BATCH_WAKE_UPON_FIFO_FULL   = 0x00000002
+};
+
+/*
+ * what field for meta_data_event_t
+ */
+enum {
+    /* a previous flush operation has completed */
+    META_DATA_FLUSH_COMPLETE = 1,
+    META_DATA_VERSION   /* always last, leave auto-assigned */
+};
+
+/**
+ * Definition of the axis used by the sensor HAL API
+ *
+ * This API is relative to the screen of the device in its default orientation,
+ * that is, if the device can be used in portrait or landscape, this API
+ * is only relative to the NATURAL orientation of the screen. In other words,
+ * the axis are not swapped when the device's screen orientation changes.
+ * Higher level services /may/ perform this transformation.
+ *
+ *   x<0         x>0
+ *                ^
+ *                |
+ *    +-----------+-->  y>0
+ *    |           |
+ *    |           |
+ *    |           |
+ *    |           |   / z<0
+ *    |           |  /
+ *    |           | /
+ *    O-----------+/
+ *    |[]  [ ]  []/
+ *    +----------/+     y<0
+ *              /
+ *             /
+ *           |/ z>0 (toward the sky)
+ *
+ *    O: Origin (x=0,y=0,z=0)
+ *
+ */
+
+/*
+ * Interaction with suspend mode
+ *
+ * Unless otherwise noted, an enabled sensor shall not prevent the
+ * SoC to go into suspend mode. It is the responsibility of applications
+ * to keep a partial wake-lock should they wish to receive sensor
+ * events while the screen is off. While in suspend mode, and unless
+ * otherwise noted (batch mode, sensor particularities, ...), enabled sensors'
+ * events are lost.
+ *
+ * Note that conceptually, the sensor itself is not de-activated while in
+ * suspend mode -- it's just that the data it returns are lost. As soon as
+ * the SoC gets out of suspend mode, operations resume as usual. Of course,
+ * in practice sensors shall be disabled while in suspend mode to
+ * save power, unless batch mode is active, in which case they must
+ * continue fill their internal FIFO (see the documentation of batch() to
+ * learn how suspend interacts with batch mode).
+ *
+ * In batch mode, and only when the flag SENSORS_BATCH_WAKE_UPON_FIFO_FULL is
+ * set and supported, the specified sensor must be able to wake-up the SoC and
+ * be able to buffer at least 10 seconds worth of the requested sensor events.
+ *
+ * There are notable exceptions to this behavior, which are sensor-dependent
+ * (see sensor types definitions below)
+ *
+ *
+ * The sensor type documentation below specifies the wake-up behavior of
+ * each sensor:
+ *   wake-up: yes     this sensor must wake-up the SoC to deliver events
+ *   wake-up: no      this sensor shall not wake-up the SoC, events are dropped
+ *
+ */
+
+/*
+ * Sensor type
+ *
+ * Each sensor has a type which defines what this sensor measures and how
+ * measures are reported. All types are defined below.
+ *
+ * Device manufacturers (OEMs) can define their own sensor types, for
+ * their private use by applications or services provided by them. Such
+ * sensor types are specific to an OEM and can't be exposed in the SDK.
+ * These types must start at SENSOR_TYPE_DEVICE_PRIVATE_BASE.
+ */
+
+/*
+ * Base for device manufacturers private sensor types.
+ * These sensor types can't be exposed in the SDK.
+ */
+#define SENSOR_TYPE_DEVICE_PRIVATE_BASE     0x10000
+
+/*
+ * Sensor fusion and virtual sensors
+ *
+ * Many sensor types are or can be implemented as virtual sensors from
+ * physical sensors on the device. For instance the rotation vector sensor,
+ * orientation sensor, step-detector, step-counter, etc...
+ *
+ * From the point of view of this API these virtual sensors MUST appear as
+ * real, individual sensors. It is the responsibility of the driver and HAL
+ * to make sure this is the case.
+ *
+ * In particular, all sensors must be able to function concurrently.
+ * For example, if defining both an accelerometer and a step counter,
+ * then both must be able to work concurrently.
+ */
+
+/*
+ * Trigger modes
+ *
+ * Sensors can report events in different ways called trigger modes,
+ * each sensor type has one and only one trigger mode associated to it.
+ * Currently there are four trigger modes defined:
+ *
+ * continuous: events are reported at a constant rate defined by setDelay().
+ *             eg: accelerometers, gyroscopes.
+ * on-change:  events are reported only if the sensor's value has changed.
+ *             setDelay() is used to set a lower limit to the reporting
+ *             period (minimum time between two events).
+ *             The HAL must return an event immediately when an on-change
+ *             sensor is activated.
+ *             eg: proximity, light sensors
+ * one-shot:   upon detection of an event, the sensor deactivates itself and
+ *             then sends a single event. Order matters to avoid race
+ *             conditions. No other event is sent until the sensor get
+ *             reactivated. setDelay() is ignored.
+ *             eg: significant motion sensor
+ * special:    see details in the sensor type specification below
+ *
+ */
+
+/*
+ * SENSOR_TYPE_META_DATA
+ * trigger-mode: n/a
+ * wake-up sensor: n/a
+ *
+ * NO SENSOR OF THAT TYPE MUST BE RETURNED (*get_sensors_list)()
+ *
+ * SENSOR_TYPE_META_DATA is a special token used to populate the
+ * sensors_meta_data_event structure. It doesn't correspond to a physical
+ * sensor. sensors_meta_data_event are special, they exist only inside
+ * the HAL and are generated spontaneously, as opposed to be related to
+ * a physical sensor.
+ *
+ *   sensors_meta_data_event_t.version must be META_DATA_VERSION
+ *   sensors_meta_data_event_t.sensor must be 0
+ *   sensors_meta_data_event_t.type must be SENSOR_TYPE_META_DATA
+ *   sensors_meta_data_event_t.reserved must be 0
+ *   sensors_meta_data_event_t.timestamp must be 0
+ *
+ * The payload is a meta_data_event_t, where:
+ * meta_data_event_t.what can take the following values:
+ *
+ * META_DATA_FLUSH_COMPLETE
+ *   This event indicates that a previous (*flush)() call has completed for the sensor
+ *   handle specified in meta_data_event_t.sensor.
+ *   see (*flush)() for more details
+ *
+ * All other values for meta_data_event_t.what are reserved and
+ * must not be used.
+ *
+ */
+#define SENSOR_TYPE_META_DATA                           (0)
+
+/*
+ * SENSOR_TYPE_ACCELEROMETER
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ *  All values are in SI units (m/s^2) and measure the acceleration of the
+ *  device minus the force of gravity.
+ *
+ *  Acceleration sensors return sensor events for all 3 axes at a constant
+ *  rate defined by setDelay().
+ *
+ *  x: Acceleration on the x-axis
+ *  y: Acceleration on the y-axis
+ *  z: Acceleration on the z-axis
+ *
+ * Note that the readings from the accelerometer include the acceleration
+ * due to gravity (which is opposite to the direction of the gravity vector).
+ *
+ *  Examples:
+ *    The norm of <x, y, z>  should be close to 0 when in free fall.
+ *
+ *    When the device lies flat on a table and is pushed on its left side
+ *    toward the right, the x acceleration value is positive.
+ *
+ *    When the device lies flat on a table, the acceleration value is +9.81,
+ *    which correspond to the acceleration of the device (0 m/s^2) minus the
+ *    force of gravity (-9.81 m/s^2).
+ *
+ *    When the device lies flat on a table and is pushed toward the sky, the
+ *    acceleration value is greater than +9.81, which correspond to the
+ *    acceleration of the device (+A m/s^2) minus the force of
+ *    gravity (-9.81 m/s^2).
+ */
+#define SENSOR_TYPE_ACCELEROMETER                    (1)
+
+/*
+ * SENSOR_TYPE_GEOMAGNETIC_FIELD
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ *  All values are in micro-Tesla (uT) and measure the geomagnetic
+ *  field in the X, Y and Z axis.
+ *
+ *  Returned values include calibration mechanisms such that the vector is
+ *  aligned with the magnetic declination and heading of the earth's
+ *  geomagnetic field.
+ *
+ *  Magnetic Field sensors return sensor events for all 3 axes at a constant
+ *  rate defined by setDelay().
+ */
+#define SENSOR_TYPE_GEOMAGNETIC_FIELD                (2)
+#define SENSOR_TYPE_MAGNETIC_FIELD  SENSOR_TYPE_GEOMAGNETIC_FIELD
+
+/*
+ * SENSOR_TYPE_ORIENTATION
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ * All values are angles in degrees.
+ *
+ * Orientation sensors return sensor events for all 3 axes at a constant
+ * rate defined by setDelay().
+ *
+ * azimuth: angle between the magnetic north direction and the Y axis, around
+ *  the Z axis (0<=azimuth<360).
+ *      0=North, 90=East, 180=South, 270=West
+ *
+ * pitch: Rotation around X axis (-180<=pitch<=180), with positive values when
+ *  the z-axis moves toward the y-axis.
+ *
+ * roll: Rotation around Y axis (-90<=roll<=90), with positive values when
+ *  the x-axis moves towards the z-axis.
+ *
+ * Note: For historical reasons the roll angle is positive in the clockwise
+ *  direction (mathematically speaking, it should be positive in the
+ *  counter-clockwise direction):
+ *
+ *                Z
+ *                ^
+ *  (+roll)  .--> |
+ *          /     |
+ *         |      |  roll: rotation around Y axis
+ *     X <-------(.)
+ *                 Y
+ *       note that +Y == -roll
+ *
+ *
+ *
+ * Note: This definition is different from yaw, pitch and roll used in aviation
+ *  where the X axis is along the long side of the plane (tail to nose).
+ */
+#define SENSOR_TYPE_ORIENTATION                      (3)
+
+/*
+ * SENSOR_TYPE_GYROSCOPE
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ *  All values are in radians/second and measure the rate of rotation
+ *  around the X, Y and Z axis.  The coordinate system is the same as is
+ *  used for the acceleration sensor. Rotation is positive in the
+ *  counter-clockwise direction (right-hand rule). That is, an observer
+ *  looking from some positive location on the x, y or z axis at a device
+ *  positioned on the origin would report positive rotation if the device
+ *  appeared to be rotating counter clockwise. Note that this is the
+ *  standard mathematical definition of positive rotation and does not agree
+ *  with the definition of roll given earlier.
+ *  The range should at least be 17.45 rad/s (ie: ~1000 deg/s).
+ *
+ *  automatic gyro-drift compensation is allowed but not required.
+ */
+#define SENSOR_TYPE_GYROSCOPE                        (4)
+
+/*
+ * SENSOR_TYPE_LIGHT
+ * trigger-mode: on-change
+ * wake-up sensor: no
+ *
+ * The light sensor value is returned in SI lux units.
+ */
+#define SENSOR_TYPE_LIGHT                            (5)
+
+/*
+ * SENSOR_TYPE_PRESSURE
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ * The pressure sensor return the athmospheric pressure in hectopascal (hPa)
+ */
+#define SENSOR_TYPE_PRESSURE                         (6)
+
+/* SENSOR_TYPE_TEMPERATURE is deprecated in the HAL */
+#define SENSOR_TYPE_TEMPERATURE                      (7)
+
+/*
+ * SENSOR_TYPE_PROXIMITY
+ * trigger-mode: on-change
+ * wake-up sensor: yes
+ *
+ * The distance value is measured in centimeters.  Note that some proximity
+ * sensors only support a binary "close" or "far" measurement.  In this case,
+ * the sensor should report its maxRange value in the "far" state and a value
+ * less than maxRange in the "near" state.
+ */
+#define SENSOR_TYPE_PROXIMITY                        (8)
+
+/*
+ * SENSOR_TYPE_GRAVITY
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ * A gravity output indicates the direction of and magnitude of gravity in
+ * the devices's coordinates.  On Earth, the magnitude is 9.8 m/s^2.
+ * Units are m/s^2.  The coordinate system is the same as is used for the
+ * acceleration sensor. When the device is at rest, the output of the
+ * gravity sensor should be identical to that of the accelerometer.
+ */
+#define SENSOR_TYPE_GRAVITY                          (9)
+
+/*
+ * SENSOR_TYPE_LINEAR_ACCELERATION
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ * Indicates the linear acceleration of the device in device coordinates,
+ * not including gravity.
+ *
+ * The output is conceptually:
+ *    output of TYPE_ACCELERATION - output of TYPE_GRAVITY
+ *
+ * Readings on all axes should be close to 0 when device lies on a table.
+ * Units are m/s^2.
+ * The coordinate system is the same as is used for the acceleration sensor.
+ */
+#define SENSOR_TYPE_LINEAR_ACCELERATION             (10)
+
+/*
+ * SENSOR_TYPE_ROTATION_VECTOR
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ * The rotation vector symbolizes the orientation of the device relative to the
+ * East-North-Up coordinates frame. It is usually obtained by integration of
+ * accelerometer, gyroscope and magnetometer readings.
+ *
+ * The East-North-Up coordinate system is defined as a direct orthonormal basis
+ * where:
+ * - X points east and is tangential to the ground.
+ * - Y points north and is tangential to the ground.
+ * - Z points towards the sky and is perpendicular to the ground.
+ *
+ * The orientation of the phone is represented by the rotation necessary to
+ * align the East-North-Up coordinates with the phone's coordinates. That is,
+ * applying the rotation to the world frame (X,Y,Z) would align them with the
+ * phone coordinates (x,y,z).
+ *
+ * The rotation can be seen as rotating the phone by an angle theta around
+ * an axis rot_axis to go from the reference (East-North-Up aligned) device
+ * orientation to the current device orientation.
+ *
+ * The rotation is encoded as the 4 (reordered) components of a unit quaternion:
+ *   sensors_event_t.data[0] = rot_axis.x*sin(theta/2)
+ *   sensors_event_t.data[1] = rot_axis.y*sin(theta/2)
+ *   sensors_event_t.data[2] = rot_axis.z*sin(theta/2)
+ *   sensors_event_t.data[3] = cos(theta/2)
+ * where
+ *   - rot_axis.x,y,z are the North-East-Up coordinates of a unit length vector
+ *     representing the rotation axis
+ *   - theta is the rotation angle
+ *
+ * The quaternion must be of norm 1 (it is a unit quaternion). Failure to ensure
+ * this will cause erratic client behaviour.
+ *
+ * In addition, this sensor reports an estimated heading accuracy.
+ *   sensors_event_t.data[4] = estimated_accuracy (in radians)
+ * The heading error must be less than estimated_accuracy 95% of the time
+ *
+ * This sensor must use a gyroscope and an accelerometer as main orientation
+ * change input.
+ *
+ * This sensor can also include magnetometer input to make up for gyro drift,
+ * but it cannot be implemented using only a magnetometer.
+ */
+#define SENSOR_TYPE_ROTATION_VECTOR                 (11)
+
+/*
+ * SENSOR_TYPE_RELATIVE_HUMIDITY
+ * trigger-mode: on-change
+ * wake-up sensor: no
+ *
+ * A relative humidity sensor measures relative ambient air humidity and
+ * returns a value in percent.
+ */
+#define SENSOR_TYPE_RELATIVE_HUMIDITY               (12)
+
+/*
+ * SENSOR_TYPE_AMBIENT_TEMPERATURE
+ * trigger-mode: on-change
+ * wake-up sensor: no
+ *
+ * The ambient (room) temperature in degree Celsius.
+ */
+#define SENSOR_TYPE_AMBIENT_TEMPERATURE             (13)
+
+/*
+ * SENSOR_TYPE_MAGNETIC_FIELD_UNCALIBRATED
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ *  Similar to SENSOR_TYPE_MAGNETIC_FIELD, but the hard iron calibration is
+ *  reported separately instead of being included in the measurement.
+ *  Factory calibration and temperature compensation should still be applied to
+ *  the "uncalibrated" measurement.
+ *  Separating away the hard iron calibration estimation allows the system to
+ *  better recover from bad hard iron estimation.
+ *
+ *  All values are in micro-Tesla (uT) and measure the ambient magnetic
+ *  field in the X, Y and Z axis. Assumptions that the the magnetic field
+ *  is due to the Earth's poles should be avoided.
+ *
+ *  The uncalibrated_magnetic event contains
+ *  - 3 fields for uncalibrated measurement: x_uncalib, y_uncalib, z_uncalib.
+ *    Each is a component of the measured magnetic field, with soft iron
+ *    and temperature compensation applied, but not hard iron calibration.
+ *    These values should be continuous (no re-calibration should cause a jump).
+ *  - 3 fields for hard iron bias estimates: x_bias, y_bias, z_bias.
+ *    Each field is a component of the estimated hard iron calibration.
+ *    They represent the offsets to apply to the calibrated readings to obtain
+ *    uncalibrated readings (x_uncalib ~= x_calibrated + x_bias)
+ *    These values are expected to jump as soon as the estimate of the hard iron
+ *    changes, and they should be stable the rest of the time.
+ *
+ *  If this sensor is present, then the corresponding
+ *  SENSOR_TYPE_MAGNETIC_FIELD must be present and both must return the
+ *  same sensor_t::name and sensor_t::vendor.
+ *
+ *  Minimum filtering should be applied to this sensor. In particular, low pass
+ *  filters should be avoided.
+ *
+ * See SENSOR_TYPE_MAGNETIC_FIELD for more information
+ */
+#define SENSOR_TYPE_MAGNETIC_FIELD_UNCALIBRATED     (14)
+
+/*
+ * SENSOR_TYPE_GAME_ROTATION_VECTOR
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ *  Similar to SENSOR_TYPE_ROTATION_VECTOR, but not using the geomagnetic
+ *  field. Therefore the Y axis doesn't point north, but instead to some other
+ *  reference. That reference is allowed to drift by the same order of
+ *  magnitude than the gyroscope drift around the Z axis.
+ *
+ *  This sensor does not report an estimated heading accuracy:
+ *    sensors_event_t.data[4] is reserved and should be set to 0
+ *
+ *  In the ideal case, a phone rotated and returning to the same real-world
+ *  orientation should report the same game rotation vector
+ *  (without using the earth's geomagnetic field).
+ *
+ *  This sensor must be based on a gyroscope. It cannot be implemented using
+ *  a magnetometer.
+ *
+ * see SENSOR_TYPE_ROTATION_VECTOR for more details
+ */
+#define SENSOR_TYPE_GAME_ROTATION_VECTOR            (15)
+
+/*
+ * SENSOR_TYPE_GYROSCOPE_UNCALIBRATED
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ *  All values are in radians/second and measure the rate of rotation
+ *  around the X, Y and Z axis. An estimation of the drift on each axis is
+ *  reported as well.
+ *
+ *  No gyro-drift compensation shall be performed.
+ *  Factory calibration and temperature compensation should still be applied
+ *  to the rate of rotation (angular speeds).
+ *
+ *  The coordinate system is the same as is
+ *  used for the acceleration sensor. Rotation is positive in the
+ *  counter-clockwise direction (right-hand rule). That is, an observer
+ *  looking from some positive location on the x, y or z axis at a device
+ *  positioned on the origin would report positive rotation if the device
+ *  appeared to be rotating counter clockwise. Note that this is the
+ *  standard mathematical definition of positive rotation and does not agree
+ *  with the definition of roll given earlier.
+ *  The range should at least be 17.45 rad/s (ie: ~1000 deg/s).
+ *
+ *  Content of an uncalibrated_gyro event: (units are rad/sec)
+ *   x_uncalib : angular speed (w/o drift compensation) around the X axis
+ *   y_uncalib : angular speed (w/o drift compensation) around the Y axis
+ *   z_uncalib : angular speed (w/o drift compensation) around the Z axis
+ *   x_bias : estimated drift around X axis in rad/s
+ *   y_bias : estimated drift around Y axis in rad/s
+ *   z_bias : estimated drift around Z axis in rad/s
+ *
+ *  IMPLEMENTATION NOTES:
+ *
+ *  If the implementation is not able to estimate the drift, then this
+ *  sensor MUST NOT be reported by this HAL. Instead, the regular
+ *  SENSOR_TYPE_GYROSCOPE is used without drift compensation.
+ *
+ *  If this sensor is present, then the corresponding
+ *  SENSOR_TYPE_GYROSCOPE must be present and both must return the
+ *  same sensor_t::name and sensor_t::vendor.
+ */
+#define SENSOR_TYPE_GYROSCOPE_UNCALIBRATED          (16)
+
+/*
+ * SENSOR_TYPE_SIGNIFICANT_MOTION
+ * trigger-mode: one-shot
+ * wake-up sensor: yes
+ *
+ * A sensor of this type triggers an event each time significant motion
+ * is detected and automatically disables itself.
+ * The only allowed value to return is 1.0.
+ *
+ * A significant motion is a motion that might lead to a change in the user
+ * location.
+ * Examples of such motions are:
+ *   walking, biking, sitting in a moving car, coach or train.
+ * Examples of situations that should not trigger significant motion:
+ * - phone in pocket and person is not moving
+ * - phone is on a table, even if the table shakes a bit due to nearby traffic
+ *   or washing machine
+ *
+ * A note on false positive / false negative / power consumption tradeoff
+ *  - The goal of this sensor is to save power.
+ *  - Triggering an event when the user is not moving (false positive) is costly
+ *    in terms of power, so it should be avoided.
+ *  - Not triggering an event when the user is moving (false negative) is
+ *    acceptable as long as it is not done repeatedly. If the user has been
+ *    walking for 10 seconds, not triggering an event within those 10 seconds
+ *    is not acceptable.
+ *
+ *  IMPORTANT NOTE: this sensor type is very different from other types
+ *  in that it must work when the screen is off without the need of
+ *  holding a partial wake-lock and MUST allow the SoC to go into suspend.
+ *  When significant motion is detected, the sensor must awaken the SoC and
+ *  the event be reported.
+ *
+ *  If a particular hardware cannot support this mode of operation then this
+ *  sensor type MUST NOT be reported by the HAL. ie: it is not acceptable
+ *  to "emulate" this sensor in the HAL.
+ *
+ *  The whole point of this sensor type is to save power by keeping the
+ *  SoC in suspend mode when the device is at rest.
+ *
+ *  When the sensor is not activated, it must also be deactivated in the
+ *  hardware: it must not wake up the SoC anymore, even in case of
+ *  significant motion.
+ *
+ *  setDelay() has no effect and is ignored.
+ *  Once a "significant motion" event is returned, a sensor of this type
+ *  must disables itself automatically, as if activate(..., 0) had been called.
+ */
+
+#define SENSOR_TYPE_SIGNIFICANT_MOTION              (17)
+
+/*
+ * SENSOR_TYPE_STEP_DETECTOR
+ * trigger-mode: special
+ * wake-up sensor: no
+ *
+ * A sensor of this type triggers an event each time a step is taken
+ * by the user. The only allowed value to return is 1.0 and an event is
+ * generated for each step. Like with any other event, the timestamp
+ * indicates when the event (here the step) occurred, this corresponds to when
+ * the foot hit the ground, generating a high variation in acceleration.
+ *
+ * While this sensor operates, it shall not disrupt any other sensors, in
+ * particular, but not limited to, the accelerometer; which might very well
+ * be in use as well.
+ *
+ * This sensor must be low power. That is, if the step detection cannot be
+ * done in hardware, this sensor should not be defined. Also, when the
+ * step detector is activated and the accelerometer is not, only steps should
+ * trigger interrupts (not accelerometer data).
+ *
+ * setDelay() has no impact on this sensor type
+ */
+
+#define SENSOR_TYPE_STEP_DETECTOR                   (18)
+
+/*
+ * SENSOR_TYPE_STEP_COUNTER
+ * trigger-mode: on-change
+ * wake-up sensor: no
+ *
+ * A sensor of this type returns the number of steps taken by the user since
+ * the last reboot while activated. The value is returned as a uint64_t and is
+ * reset to zero only on a system / android reboot.
+ *
+ * The timestamp of the event is set to the time when the first step
+ * for that event was taken.
+ * See SENSOR_TYPE_STEP_DETECTOR for the signification of the time of a step.
+ *
+ *  The minimum size of the hardware's internal counter shall be 16 bits
+ *  (this restriction is here to avoid too frequent wake-ups when the
+ *  delay is very large).
+ *
+ *  IMPORTANT NOTE: this sensor type is different from other types
+ *  in that it must work when the screen is off without the need of
+ *  holding a partial wake-lock and MUST allow the SoC to go into suspend.
+ *  Unlike other sensors, while in suspend mode this sensor must stay active,
+ *  no events are reported during that time but, steps continue to be
+ *  accounted for; an event will be reported as soon as the SoC resumes if
+ *  the timeout has expired.
+ *
+ *    In other words, when the screen is off and the device allowed to
+ *    go into suspend mode, we don't want to be woken up, regardless of the
+ *    setDelay() value, but the steps shall continue to be counted.
+ *
+ *    The driver must however ensure that the internal step count never
+ *    overflows. It is allowed in this situation to wake the SoC up so the
+ *    driver can do the counter maintenance.
+ *
+ *  While this sensor operates, it shall not disrupt any other sensors, in
+ *  particular, but not limited to, the accelerometer; which might very well
+ *  be in use as well.
+ *
+ *  If a particular hardware cannot support these modes of operation then this
+ *  sensor type MUST NOT be reported by the HAL. ie: it is not acceptable
+ *  to "emulate" this sensor in the HAL.
+ *
+ * This sensor must be low power. That is, if the step detection cannot be
+ * done in hardware, this sensor should not be defined. Also, when the
+ * step counter is activated and the accelerometer is not, only steps should
+ * trigger interrupts (not accelerometer data).
+ *
+ *  The whole point of this sensor type is to save power by keeping the
+ *  SoC in suspend mode when the device is at rest.
+ */
+
+#define SENSOR_TYPE_STEP_COUNTER                    (19)
+
+/*
+ * SENSOR_TYPE_GEOMAGNETIC_ROTATION_VECTOR
+ * trigger-mode: continuous
+ * wake-up sensor: no
+ *
+ *  Similar to SENSOR_TYPE_ROTATION_VECTOR, but using a magnetometer instead
+ *  of using a gyroscope.
+ *
+ *  This sensor must be based on a magnetometer. It cannot be implemented using
+ *  a gyroscope, and gyroscope input cannot be used by this sensor, as the
+ *  goal of this sensor is to be low power.
+ *  The accelerometer can be (and usually is) used.
+ *
+ *  Just like SENSOR_TYPE_ROTATION_VECTOR, this sensor reports an estimated
+ *  heading accuracy:
+ *    sensors_event_t.data[4] = estimated_accuracy (in radians)
+ *  The heading error must be less than estimated_accuracy 95% of the time
+ *
+ * see SENSOR_TYPE_ROTATION_VECTOR for more details
+ */
+#define SENSOR_TYPE_GEOMAGNETIC_ROTATION_VECTOR            (20)
+
+/**
+ * Values returned by the accelerometer in various locations in the universe.
+ * all values are in SI units (m/s^2)
+ */
+#define GRAVITY_SUN                 (275.0f)
+#define GRAVITY_EARTH               (9.80665f)
+
+/** Maximum magnetic field on Earth's surface */
+#define MAGNETIC_FIELD_EARTH_MAX    (60.0f)
+
+/** Minimum magnetic field on Earth's surface */
+#define MAGNETIC_FIELD_EARTH_MIN    (30.0f)
+
+/**
+ * status of orientation sensor
+ */
+#define SENSOR_STATUS_UNRELIABLE        0
+#define SENSOR_STATUS_ACCURACY_LOW      1
+#define SENSOR_STATUS_ACCURACY_MEDIUM   2
+#define SENSOR_STATUS_ACCURACY_HIGH     3
+
+/**
+ * sensor event data
+ */
+typedef struct
+{
+    union {
+        float v[3];
+        struct {
+            float x;
+            float y;
+            float z;
+        };
+        struct {
+            float azimuth;
+            float pitch;
+            float roll;
+        };
+    };
+    int8_t status;
+    uint8_t reserved[3];
+} sensors_vec_t;
+
+/**
+ * uncalibrated gyroscope and magnetometer event data
+ */
+typedef struct
+{
+  union {
+    float uncalib[3];
+    struct {
+      float x_uncalib;
+      float y_uncalib;
+      float z_uncalib;
+    };
+  };
+  union {
+    float bias[3];
+    struct {
+      float x_bias;
+      float y_bias;
+      float z_bias;
+    };
+  };
+} uncalibrated_event_t;
+
+typedef struct meta_data_event
+{
+    int32_t what;
+    int32_t sensor;
+} meta_data_event_t;
+
+/**
+ * Union of the various types of sensor data
+ * that can be returned.
+ */
+typedef struct sensors_event_t {
+    /* must be sizeof(struct sensors_event_t) */
+    int32_t version;
+
+    /* sensor identifier */
+    int32_t sensor;
+
+    /* sensor type */
+    int32_t type;
+
+    /* reserved */
+    int32_t reserved0;
+
+    /* time is in nanosecond */
+    int64_t timestamp;
+
+    union {
+        union {
+            float           data[16];
+
+            /* acceleration values are in meter per second per second (m/s^2) */
+            sensors_vec_t   acceleration;
+
+            /* magnetic vector values are in micro-Tesla (uT) */
+            sensors_vec_t   magnetic;
+
+            /* orientation values are in degrees */
+            sensors_vec_t   orientation;
+
+            /* gyroscope values are in rad/s */
+            sensors_vec_t   gyro;
+
+            /* temperature is in degrees centigrade (Celsius) */
+            float           temperature;
+
+            /* distance in centimeters */
+            float           distance;
+
+            /* light in SI lux units */
+            float           light;
+
+            /* pressure in hectopascal (hPa) */
+            float           pressure;
+
+            /* relative humidity in percent */
+            float           relative_humidity;
+
+            /* uncalibrated gyroscope values are in rad/s */
+            uncalibrated_event_t uncalibrated_gyro;
+
+            /* uncalibrated magnetometer values are in micro-Teslas */
+            uncalibrated_event_t uncalibrated_magnetic;
+
+            /* this is a special event. see SENSOR_TYPE_META_DATA above.
+             * sensors_meta_data_event_t events are all reported with a type of
+             * SENSOR_TYPE_META_DATA. The handle is ignored and must be zero.
+             */
+            meta_data_event_t meta_data;
+        };
+
+        union {
+            uint64_t        data[8];
+
+            /* step-counter */
+            uint64_t        step_counter;
+        } u64;
+    };
+    uint32_t reserved1[4];
+} sensors_event_t;
+
+/* see SENSOR_TYPE_META_DATA */
+typedef sensors_event_t sensors_meta_data_event_t;
+
+typedef struct sensor_t {
+
+    /* Name of this sensor.
+     * All sensors of the same "type" must have a different "name".
+     */
+    const char*     name;
+
+    /* vendor of the hardware part */
+    const char*     vendor;
+
+    /* version of the hardware part + driver. The value of this field
+     * must increase when the driver is updated in a way that changes the
+     * output of this sensor. This is important for fused sensors when the
+     * fusion algorithm is updated.
+     */
+    int             version;
+
+    /* handle that identifies this sensors. This handle is used to reference
+     * this sensor throughout the HAL API.
+     */
+    int             handle;
+
+    /* this sensor's type. */
+    int             type;
+
+    /* maximum range of this sensor's value in SI units */
+    float           maxRange;
+
+    /* smallest difference between two values reported by this sensor */
+    float           resolution;
+
+    /* rough estimate of this sensor's power consumption in mA */
+    float           power;
+
+    /* this value depends on the trigger mode:
+     *
+     *   continuous: minimum sample period allowed in microseconds
+     *   on-change : 0
+     *   one-shot  :-1
+     *   special   : 0, unless otherwise noted
+     */
+    int32_t         minDelay;
+
+    /* number of events reserved for this sensor in the batch mode FIFO.
+     * If there is a dedicated FIFO for this sensor, then this is the
+     * size of this FIFO. If the FIFO is shared with other sensors,
+     * this is the size reserved for that sensor and it can be zero.
+     */
+    uint32_t        fifoReservedEventCount;
+
+    /* maximum number of events of this sensor that could be batched.
+     * This is especially relevant when the FIFO is shared between
+     * several sensors; this value is then set to the size of that FIFO.
+     */
+    uint32_t        fifoMaxEventCount;
+
+    /* reserved fields, must be zero */
+    void*           reserved[6];
+} sensor_t;
+
+class SensorConfigure
+{
+    int32_t delay;
+};
+
+class Sensor;
+class SensorManager;
+typedef void (*SensorEventHandler_t)(Sensor* sensor, sensors_event_t* event, void* user_data);
+
+/**
+ * Sensor Base Class
+ */
+class Sensor
+{
+private:
+    int type;
+
+public:
+    Sensor();
+    ~Sensor();
+
+    virtual int Configure(SensorConfigure *config) = 0;
+    virtual int Activate(int enable) = 0;
+
+    virtual int Poll(sensors_event_t *events, int number, int duration) = 0;
+    virtual void GetSensor(struct sensor_t *sensor) = 0;
+
+    int GetType(void);
+
+    int Subscribe(SensorEventHandler_t *handler, void* user_data);
+    int Publish(sensors_event_t* event);
+
+protected: 
+    Sensor *next;
+	Sensor *prev;
+
+    SensorEventHandler_t *evtHandler;
+    void *userData;
+
+	friend class SensorManager;
+};
+
+/**
+ * Sensor Manager
+ */
+class SensorManager
+{
+public:
+    SensorManager();
+    ~SensorManager();
+    
+    static int RegisterSensor(Sensor* sensor);
+    static int DeregisterSensor(Sensor* sensor);
+
+    static Sensor *GetDefaultSensor(int type);
+    static int Subscribe(int type, SensorEventHandler_t *handler, void* user_data);
+
+private:
+	Sensor* sensorList;
+};
+
+#endif
+