Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 87c9dbb7 authored by Mathias Agopian's avatar Mathias Agopian
Browse files

Uses 4-th order low-pass for extracting gravity. 

Most accelerometers have 8-bits accuracy so we beed to
reject 48dB in thestop-band, which requires a 4-th order
filter at the cut-off frequency we're using.

Change-Id: Ic00421d38d751641f86b1f3ad7663e6b44a91198
parent ddf1ceb6

services/sensorservice/GravitySensor.cpp

+1 −1
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ namespace android { 
GravitySensor::GravitySensor(sensor_t const* list, size_t count)

    : mSensorDevice(SensorDevice::getInstance()),

      mEnabled(false), mAccTime(0),

      mLowPass(M_SQRT1_2, 1),

      mLowPass(M_SQRT1_2, 1.5f),

      mX(mLowPass), mY(mLowPass), mZ(mLowPass)



{

services/sensorservice/GravitySensor.h

+1 −1
Original line number Diff line number Diff line
@@ -37,7 +37,7 @@ class GravitySensor : public SensorInterface { 
    double mAccTime;



    SecondOrderLowPassFilter mLowPass;

    BiquadFilter mX, mY, mZ;

    CascadedBiquadFilter mX, mY, mZ;



public:

    GravitySensor(sensor_t const* list, size_t count);

services/sensorservice/SecondOrderLowPassFilter.cpp

+19 −0
Original line number Diff line number Diff line
@@ -66,5 +66,24 @@ float BiquadFilter::operator()(float x) 
    return y;

}



// ---------------------------------------------------------------------------



CascadedBiquadFilter::CascadedBiquadFilter(const SecondOrderLowPassFilter& s)

    : mA(s), mB(s)

{

}



float CascadedBiquadFilter::init(float x)

{

    mA.init(x);

    mB.init(x);

    return x;

}



float CascadedBiquadFilter::operator()(float x)

{

    return mB(mA(x));

}



// ---------------------------------------------------------------------------

}; // namespace android

services/sensorservice/SecondOrderLowPassFilter.h

+12 −0
Original line number Diff line number Diff line
@@ -54,6 +54,18 @@ public: 
    float operator()(float in);

};



/*

 * Two cascaded biquad IIR filters

 * (4-poles IIR)

 */

class CascadedBiquadFilter {

    BiquadFilter mA;

    BiquadFilter mB;

public:

    CascadedBiquadFilter(const SecondOrderLowPassFilter& s);

    float init(float in);

    float operator()(float in);

};



// ---------------------------------------------------------------------------

}; // namespace android