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annotate Source/Utility/IIRFilter.cpp @ 16:61e3c9df4674

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Fix bug where TouchKeys standalone mode turns off when mode is changed.
author Andrew McPherson <andrewm@eecs.qmul.ac.uk>
date Mon, 25 Nov 2013 21:36:02 +0000
parents 3580ffe87dc8
children dfff66c07936
rev   line source
andrewm@0 1 /*
andrewm@0 2 TouchKeys: multi-touch musical keyboard control software
andrewm@0 3 Copyright (c) 2013 Andrew McPherson
andrewm@0 4
andrewm@0 5 This program is free software: you can redistribute it and/or modify
andrewm@0 6 it under the terms of the GNU General Public License as published by
andrewm@0 7 the Free Software Foundation, either version 3 of the License, or
andrewm@0 8 (at your option) any later version.
andrewm@0 9
andrewm@0 10 This program is distributed in the hope that it will be useful,
andrewm@0 11 but WITHOUT ANY WARRANTY; without even the implied warranty of
andrewm@0 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
andrewm@0 13 GNU General Public License for more details.
andrewm@0 14
andrewm@0 15 You should have received a copy of the GNU General Public License
andrewm@0 16 along with this program. If not, see <http://www.gnu.org/licenses/>.
andrewm@0 17
andrewm@0 18 =====================================================================
andrewm@0 19
andrewm@0 20 IIRFilter.cpp: template class handling an Nth-order IIR filter on data
andrewm@0 21 in a given Node.
andrewm@0 22 */
andrewm@0 23
andrewm@0 24 #include "IIRFilter.h"
andrewm@0 25 #include <cmath>
andrewm@0 26
andrewm@0 27 // These are static functions to design IIR filters specifically for floating-point datatypes.
andrewm@0 28 // vector<double> and be converted to another type at the end if needed.
andrewm@0 29
andrewm@0 30 void designFirstOrderLowpass(std::vector<double>& bCoeffs, std::vector<double>& aCoeffs,
andrewm@0 31 double cutoffFrequency, double sampleFrequency) {
andrewm@0 32 bCoeffs.clear();
andrewm@0 33 aCoeffs.clear();
andrewm@0 34
andrewm@0 35 double omega = tan(M_PI * cutoffFrequency / sampleFrequency);
andrewm@0 36 double n = 1.0 / (1.0 + omega);
andrewm@0 37
andrewm@0 38 bCoeffs.push_back(omega * n); // B0
andrewm@0 39 bCoeffs.push_back(omega * n); // B1
andrewm@0 40 aCoeffs.push_back((omega - 1) * n); // A1
andrewm@0 41 }
andrewm@0 42
andrewm@0 43 void designFirstOrderHighpass(std::vector<double>& bCoeffs, std::vector<double>& aCoeffs,
andrewm@0 44 double cutoffFrequency, double sampleFrequency) {
andrewm@0 45 bCoeffs.clear();
andrewm@0 46 aCoeffs.clear();
andrewm@0 47
andrewm@0 48 double omega = tan(M_PI * cutoffFrequency / sampleFrequency);
andrewm@0 49 double n = 1.0 / (1.0 + omega);
andrewm@0 50
andrewm@0 51 bCoeffs.push_back(n); // B0
andrewm@0 52 bCoeffs.push_back(-n); // B1
andrewm@0 53 aCoeffs.push_back((omega - 1) * n); // A1
andrewm@0 54 }
andrewm@0 55
andrewm@0 56 void designSecondOrderLowpass(std::vector<double>& bCoeffs, std::vector<double>& aCoeffs,
andrewm@0 57 double cutoffFrequency, double q, double sampleFrequency) {
andrewm@0 58 bCoeffs.clear();
andrewm@0 59 aCoeffs.clear();
andrewm@0 60
andrewm@0 61 double omega = tan(M_PI * cutoffFrequency / sampleFrequency);
andrewm@0 62 double n = 1.0 / (omega*omega + omega/q + 1.0);
andrewm@0 63 double b0 = n * omega * omega;
andrewm@0 64
andrewm@0 65 bCoeffs.push_back(b0); // B0
andrewm@0 66 bCoeffs.push_back(2.0 * b0); // B1
andrewm@0 67 bCoeffs.push_back(b0); // B2
andrewm@0 68 aCoeffs.push_back(2.0 * n * (omega * omega - 1.0)); // A1
andrewm@0 69 aCoeffs.push_back(n * (omega * omega - omega / q + 1.0));
andrewm@0 70 }
andrewm@0 71
andrewm@0 72 void designSecondOrderHighpass(std::vector<double>& bCoeffs, std::vector<double>& aCoeffs,
andrewm@0 73 double cutoffFrequency, double q, double sampleFrequency) {
andrewm@0 74 bCoeffs.clear();
andrewm@0 75 aCoeffs.clear();
andrewm@0 76
andrewm@0 77 double omega = tan(M_PI * cutoffFrequency / sampleFrequency);
andrewm@0 78 double n = 1.0 / (omega*omega + omega/q + 1.0);
andrewm@0 79
andrewm@0 80 bCoeffs.push_back(n); // B0
andrewm@0 81 bCoeffs.push_back(-2.0 * n); // B1
andrewm@0 82 bCoeffs.push_back(n); // B2
andrewm@0 83 aCoeffs.push_back(2.0 * n * (omega * omega - 1.0)); // A1
andrewm@0 84 aCoeffs.push_back(n * (omega * omega - omega / q + 1.0));
andrewm@0 85 }
andrewm@0 86
andrewm@0 87 void designSecondOrderBandpass(std::vector<double>& bCoeffs, std::vector<double>& aCoeffs,
andrewm@0 88 double cutoffFrequency, double q, double sampleFrequency) {
andrewm@0 89 bCoeffs.clear();
andrewm@0 90 aCoeffs.clear();
andrewm@0 91
andrewm@0 92 double omega = tan(M_PI * cutoffFrequency / sampleFrequency);
andrewm@0 93 double n = 1.0 / (omega*omega + omega/q + 1.0);
andrewm@0 94 double b0 = n * omega / q;
andrewm@0 95 bCoeffs.push_back(b0); // B0
andrewm@0 96 bCoeffs.push_back(0.0); // B1
andrewm@0 97 bCoeffs.push_back(-b0); // B2
andrewm@0 98 aCoeffs.push_back(2.0 * n * (omega * omega - 1.0)); // A1
andrewm@0 99 aCoeffs.push_back(n * (omega * omega - omega / q + 1.0));
andrewm@0 100 }