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159 lines
4.9 KiB
C++
159 lines
4.9 KiB
C++
//////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2015-2020 Edouard Griffiths, F4EXB //
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// //
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// See: http://www.embedded.com/design/connectivity/4025660/Detecting-CTCSS-tones-with-Goertzel-s-algorithm //
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// //
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// This program is free software; you can redistribute it and/or modify //
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// it under the terms of the GNU General Public License as published by //
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// the Free Software Foundation as version 3 of the License, or //
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// (at your option) any later version. //
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// //
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// This program is distributed in the hope that it will be useful, //
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// but WITHOUT ANY WARRANTY; without even the implied warranty of //
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
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// GNU General Public License V3 for more details. //
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// //
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// You should have received a copy of the GNU General Public License //
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// along with this program. If not, see <http://www.gnu.org/licenses/>. //
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//////////////////////////////////////////////////////////////////////////////////////////////////////////////
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#include <cmath>
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#include "dsp/ctcssdetector.h"
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CTCSSDetector::CTCSSDetector() :
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m_N(0),
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m_sampleRate(0),
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m_samplesProcessed(0),
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m_maxPowerIndex(0),
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m_toneDetected(false),
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m_maxPower(0.0)
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{
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m_k = new Real[CTCSSFrequencies::m_nbFreqs];
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m_coef = new Real[CTCSSFrequencies::m_nbFreqs];
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m_u0 = new Real[CTCSSFrequencies::m_nbFreqs];
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m_u1 = new Real[CTCSSFrequencies::m_nbFreqs];
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m_power = new Real[CTCSSFrequencies::m_nbFreqs];
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}
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CTCSSDetector::~CTCSSDetector()
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{
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delete[] m_k;
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delete[] m_coef;
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delete[] m_u0;
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delete[] m_u1;
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delete[] m_power;
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}
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void CTCSSDetector::setCoefficients(int N, int sampleRate)
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{
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m_N = N; // save the basic parameters for use during analysis
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m_sampleRate = sampleRate;
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// for each of the frequencies (tones) of interest calculate
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// k and the associated filter coefficient as per the Goertzel
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// algorithm. Note: we are using a real value (as apposed to
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// an integer as described in some references. k is retained
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// for later display. The tone set is specified in the
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// constructor. Notice that the resulting coefficients are
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// independent of N.
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for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
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{
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m_k[j] = ((double) m_N * CTCSSFrequencies::m_Freqs[j]) / (double)m_sampleRate;
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m_coef[j] = 2.0 * cos((2.0 * M_PI * CTCSSFrequencies::m_Freqs[j])/(double)m_sampleRate);
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}
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}
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// Analyze an input signal for the presence of CTCSS tones.
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bool CTCSSDetector::analyze(Real *sample)
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{
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feedback(*sample); // Goertzel feedback
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m_samplesProcessed += 1;
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if (m_samplesProcessed == m_N) // completed a block of N
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{
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feedForward(); // calculate the m_power at each tone
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m_samplesProcessed = 0;
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return true; // have a result
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}
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else
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{
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return false;
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}
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}
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void CTCSSDetector::feedback(Real in)
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{
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Real t;
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// feedback for each tone
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for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
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{
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t = m_u0[j];
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m_u0[j] = in + (m_coef[j] * m_u0[j]) - m_u1[j];
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m_u1[j] = t;
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}
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}
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void CTCSSDetector::feedForward()
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{
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initializePower();
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for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
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{
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m_power[j] = (m_u0[j] * m_u0[j]) + (m_u1[j] * m_u1[j]) - (m_coef[j] * m_u0[j] * m_u1[j]);
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m_u0[j] = m_u1[j] = 0.0; // reset for next block.
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}
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evaluatePower();
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}
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void CTCSSDetector::reset()
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{
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for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
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{
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m_power[j] = m_u0[j] = m_u1[j] = 0.0; // reset
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}
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m_samplesProcessed = 0;
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m_maxPower = 0.0;
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m_maxPowerIndex = 0;
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m_toneDetected = false;
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}
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void CTCSSDetector::initializePower()
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{
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for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
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{
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m_power[j] = 0.0; // reset
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}
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}
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void CTCSSDetector::evaluatePower()
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{
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Real sumPower = 0.0;
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Real aboveAvg = 2.0; // Arbitrary max m_power above average threshold
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m_maxPower = 0.0;
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for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
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{
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sumPower += m_power[j];
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if (m_power[j] > m_maxPower)
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{
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m_maxPower = m_power[j];
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m_maxPowerIndex = j;
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}
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}
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m_toneDetected = (m_maxPower > (sumPower/CTCSSFrequencies::m_nbFreqs) + aboveAvg);
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}
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