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sdrangel/sdrbase/dsp/ctcssdetector.cpp
2020-11-14 11:13:32 +01:00

159 lines
4.9 KiB
C++

//////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2015-2020 Edouard Griffiths, F4EXB //
// //
// See: http://www.embedded.com/design/connectivity/4025660/Detecting-CTCSS-tones-with-Goertzel-s-algorithm //
// //
// 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 as 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 V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
//////////////////////////////////////////////////////////////////////////////////////////////////////////////
#include <cmath>
#include "dsp/ctcssdetector.h"
CTCSSDetector::CTCSSDetector() :
m_N(0),
m_sampleRate(0),
m_samplesProcessed(0),
m_maxPowerIndex(0),
m_toneDetected(false),
m_maxPower(0.0)
{
m_k = new Real[CTCSSFrequencies::m_nbFreqs];
m_coef = new Real[CTCSSFrequencies::m_nbFreqs];
m_u0 = new Real[CTCSSFrequencies::m_nbFreqs];
m_u1 = new Real[CTCSSFrequencies::m_nbFreqs];
m_power = new Real[CTCSSFrequencies::m_nbFreqs];
}
CTCSSDetector::~CTCSSDetector()
{
delete[] m_k;
delete[] m_coef;
delete[] m_u0;
delete[] m_u1;
delete[] m_power;
}
void CTCSSDetector::setCoefficients(int N, int sampleRate)
{
m_N = N; // save the basic parameters for use during analysis
m_sampleRate = sampleRate;
// for each of the frequencies (tones) of interest calculate
// k and the associated filter coefficient as per the Goertzel
// algorithm. Note: we are using a real value (as apposed to
// an integer as described in some references. k is retained
// for later display. The tone set is specified in the
// constructor. Notice that the resulting coefficients are
// independent of N.
for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
{
m_k[j] = ((double) m_N * CTCSSFrequencies::m_Freqs[j]) / (double)m_sampleRate;
m_coef[j] = 2.0 * cos((2.0 * M_PI * CTCSSFrequencies::m_Freqs[j])/(double)m_sampleRate);
}
}
// Analyze an input signal for the presence of CTCSS tones.
bool CTCSSDetector::analyze(Real *sample)
{
feedback(*sample); // Goertzel feedback
m_samplesProcessed += 1;
if (m_samplesProcessed == m_N) // completed a block of N
{
feedForward(); // calculate the m_power at each tone
m_samplesProcessed = 0;
return true; // have a result
}
else
{
return false;
}
}
void CTCSSDetector::feedback(Real in)
{
Real t;
// feedback for each tone
for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
{
t = m_u0[j];
m_u0[j] = in + (m_coef[j] * m_u0[j]) - m_u1[j];
m_u1[j] = t;
}
}
void CTCSSDetector::feedForward()
{
initializePower();
for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
{
m_power[j] = (m_u0[j] * m_u0[j]) + (m_u1[j] * m_u1[j]) - (m_coef[j] * m_u0[j] * m_u1[j]);
m_u0[j] = m_u1[j] = 0.0; // reset for next block.
}
evaluatePower();
}
void CTCSSDetector::reset()
{
for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
{
m_power[j] = m_u0[j] = m_u1[j] = 0.0; // reset
}
m_samplesProcessed = 0;
m_maxPower = 0.0;
m_maxPowerIndex = 0;
m_toneDetected = false;
}
void CTCSSDetector::initializePower()
{
for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
{
m_power[j] = 0.0; // reset
}
}
void CTCSSDetector::evaluatePower()
{
Real sumPower = 0.0;
Real aboveAvg = 2.0; // Arbitrary max m_power above average threshold
m_maxPower = 0.0;
for (int j = 0; j < CTCSSFrequencies::m_nbFreqs; ++j)
{
sumPower += m_power[j];
if (m_power[j] > m_maxPower)
{
m_maxPower = m_power[j];
m_maxPowerIndex = j;
}
}
m_toneDetected = (m_maxPower > (sumPower/CTCSSFrequencies::m_nbFreqs) + aboveAvg);
}