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LibrePilot/flight/libraries/math/butterworth.h

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/**
******************************************************************************
* @addtogroup OpenPilot Math Utilities
* @{
* @addtogroup Butterworth low pass filter
* @{
*
* @file butterworth.h
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2014.
* @brief Direct form two of a second order Butterworth low pass filter
*
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef BUTTERWORTH_H
#define BUTTERWORTH_H
// Coefficients of second order Butterworth biquadratic filter in direct from 2
struct ButterWorthDF2Filter {
float b0;
float a1;
float a2;
};
// Function declarations
void InitButterWorthDF2Filter(const float ff, struct ButterWorthDF2Filter *filterPtr);
void InitButterWorthDF2Values(const float x0, const struct ButterWorthDF2Filter *filterPtr, float *wn1Ptr, float *wn2Ptr);
float FilterButterWorthDF2(const float xn, const struct ButterWorthDF2Filter *filterPtr, float *wn1Ptr, float *wn2Ptr);
#endif