#include <ctcssdetector.h>

Public Member Functions
	CTCSSDetector ()

	CTCSSDetector (int _nTones, Real *tones)

virtual	~CTCSSDetector ()

void	setCoefficients (int zN, int SampleRate)

void	setThreshold (double thold)

bool	analyze (Real *sample)

int	getNTones () const

const Real *	getToneSet () const

bool	getDetectedTone (int &maxTone) const

Real	getMaxPower () const

void	reset ()

Protected Member Functions
virtual void	initializePower ()

virtual void	evaluatePower ()

void	feedback (Real sample)

void	feedForward ()

Private Attributes
int	N

int	sampleRate

int	nTones

int	samplesProcessed

int	maxPowerIndex

bool	toneDetected

Real	maxPower

Real *	k

Real *	coef

Real *	toneSet

Real *	u0

Real *	u1

Real *	power

Detailed Description

CTCSSDetector: Continuous Tone Coded Squelch System tone detector class based on the Modified Goertzel algorithm.

Definition at line 19 of file ctcssdetector.h.

Constructor & Destructor Documentation

◆ CTCSSDetector() [1/2]

CTCSSDetector::CTCSSDetector ( )

Definition at line 13 of file ctcssdetector.cpp.

References coef, k, nTones, power, toneSet, u0, and u1.

                              :
             N(0),
             sampleRate(0),
             samplesProcessed(0),
             maxPowerIndex(0),
             toneDetected(false),
             maxPower(0.0)
 {
     nTones = 32;
     k = new Real[nTones];
     coef = new Real[nTones];
     toneSet = new Real[nTones];
     u0 = new Real[nTones];
     u1 = new Real[nTones];
     power = new Real[nTones];
 
     // The 32 EIA standard tones
     toneSet[0]  = 67.0;
     toneSet[1]  = 71.9;
     toneSet[2]  = 74.4;
     toneSet[3]  = 77.0;
     toneSet[4]  = 79.7;
     toneSet[5]  = 82.5;
     toneSet[6]  = 85.4;
     toneSet[7]  = 88.5;
     toneSet[8]  = 91.5;
     toneSet[9]  = 94.8;
     toneSet[10]  = 97.4;
     toneSet[11] = 100.0;
     toneSet[12] = 103.5;
     toneSet[13] = 107.2;
     toneSet[14] = 110.9;
     toneSet[15] = 114.8;
     toneSet[16] = 118.8;
     toneSet[17] = 123.0;
     toneSet[18] = 127.3;
     toneSet[19] = 131.8;
     toneSet[20] = 136.5;
     toneSet[21] = 141.3;
     toneSet[22] = 146.2;
     toneSet[23] = 151.4;
     toneSet[24] = 156.7;
     toneSet[25] = 162.2;
     toneSet[26] = 167.9;
     toneSet[27] = 173.8;
     toneSet[28] = 179.9;
     toneSet[29] = 186.2;
     toneSet[30] = 192.8;
     toneSet[31] = 203.5;
 }

◆ CTCSSDetector() [2/2]

CTCSSDetector::CTCSSDetector	(	int	_nTones,
		Real *	tones
	)

Definition at line 64 of file ctcssdetector.cpp.

References coef, k, nTones, power, toneSet, u0, and u1.

                                                      :
             N(0),
             sampleRate(0),
             samplesProcessed(0),
             maxPowerIndex(0),
             toneDetected(false),
             maxPower(0.0)
 {
     nTones = _nTones;
     k = new Real[nTones];
     coef = new Real[nTones];
     toneSet = new Real[nTones];
     u0 = new Real[nTones];
     u1 = new Real[nTones];
     power = new Real[nTones];
 
     for (int j = 0; j < nTones; ++j)
     {
         toneSet[j] = tones[j];
     }
 }

◆ ~CTCSSDetector()

CTCSSDetector::~CTCSSDetector ( )

virtual

Definition at line 87 of file ctcssdetector.cpp.

References coef, k, power, toneSet, u0, and u1.

 {
     delete[] k;
     delete[] coef;
     delete[] toneSet;
     delete[] u0;
     delete[] u1;
     delete[] power;
 }

Member Function Documentation

◆ analyze()

bool CTCSSDetector::analyze ( Real * sample )

Definition at line 119 of file ctcssdetector.cpp.

References feedback(), feedForward(), N, and samplesProcessed.

Referenced by NFMDemod::processOneSample().

 {
 
     feedback(*sample); // Goertzel feedback
     samplesProcessed += 1;
 
     if (samplesProcessed == N) // completed a block of N
     {
         feedForward(); // calculate the power at each tone
         samplesProcessed = 0;
         return true; // have a result
     }
     else
     {
         return false;
     }
 }

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◆ evaluatePower()

void CTCSSDetector::evaluatePower ( )

protectedvirtual

Definition at line 189 of file ctcssdetector.cpp.

References maxPower, maxPowerIndex, nTones, power, and toneDetected.

Referenced by feedForward().

 {
     Real sumPower = 0.0;
     Real aboveAvg = 2.0; // Arbitrary max power above average threshold
     maxPower = 0.0;
 
     for (int j = 0; j < nTones; ++j)
     {
         sumPower += power[j];
 
         if (power[j] > maxPower)
         {
             maxPower = power[j];
             maxPowerIndex = j;
         }
     }
 
     toneDetected = (maxPower > (sumPower/nTones) + aboveAvg);
 }

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◆ feedback()

void CTCSSDetector::feedback ( Real sample )

protected

Definition at line 138 of file ctcssdetector.cpp.

References coef, nTones, u0, and u1.

Referenced by analyze().

 {
     Real t;
 
     // feedback for each tone
     for (int j = 0; j < nTones; ++j)
     {
         t = u0[j];
         u0[j] = in + (coef[j] * u0[j]) - u1[j];
         u1[j] = t;
     }
 }

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◆ feedForward()

void CTCSSDetector::feedForward ( )

protected

Definition at line 152 of file ctcssdetector.cpp.

References coef, evaluatePower(), initializePower(), nTones, power, u0, and u1.

Referenced by analyze().

 {
     initializePower();
 
     for (int j = 0; j < nTones; ++j)
     {
         power[j] = (u0[j] * u0[j]) + (u1[j] * u1[j]) - (coef[j] * u0[j] * u1[j]);
         u0[j] = u1[j] = 0.0; // reset for next block.
     }
 
     evaluatePower();
 }

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◆ getDetectedTone()

bool CTCSSDetector::getDetectedTone ( int & maxTone ) const

inline

Definition at line 51 of file ctcssdetector.h.

Referenced by NFMDemod::processOneSample().

     {
         maxTone = maxPowerIndex;
         return toneDetected;
     }

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◆ getMaxPower()

Real CTCSSDetector::getMaxPower ( ) const

inline

Definition at line 58 of file ctcssdetector.h.

     {
         return maxPower;
     }

◆ getNTones()

int CTCSSDetector::getNTones ( ) const

inline

Definition at line 40 of file ctcssdetector.h.

Referenced by NFMDemod::getCtcssToneSet().

                           {
         return nTones;
     }

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◆ getToneSet()

const Real* CTCSSDetector::getToneSet ( ) const

inline

Definition at line 45 of file ctcssdetector.h.

Referenced by NFMDemod::getCtcssToneSet(), NFMDemod::processOneSample(), and NFMDemod::webapiFormatChannelReport().

     {
         return toneSet;
     }

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◆ initializePower()

void CTCSSDetector::initializePower ( )

protectedvirtual

Definition at line 180 of file ctcssdetector.cpp.

References nTones, and power.

Referenced by feedForward().

 {
     for (int j = 0; j < nTones; ++j)
     {
         power[j] = 0.0; // reset
     }
 }

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◆ reset()

void CTCSSDetector::reset ( )

Definition at line 166 of file ctcssdetector.cpp.

References maxPower, maxPowerIndex, nTones, power, samplesProcessed, toneDetected, u0, and u1.

 {
     for (int j = 0; j < nTones; ++j)
     {
         power[j] = u0[j] = u1[j] = 0.0; // reset
     }
 
     samplesProcessed = 0;
     maxPower = 0.0;
     maxPowerIndex = 0;
     toneDetected = false;
 }

◆ setCoefficients()

void CTCSSDetector::setCoefficients	(	int	zN,
		int	SampleRate
	)

Definition at line 98 of file ctcssdetector.cpp.

References coef, cos(), k, M_PI, N, nTones, sampleRate, and toneSet.

Referenced by NFMDemod::applyAudioSampleRate(), and NFMDemod::NFMDemod().

 {
     N = zN;                   // save the basic parameters for use during analysis
     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 < nTones; ++j)
     {
         k[j] = ((double)N * toneSet[j]) / (double)sampleRate;
         coef[j] = 2.0 * cos((2.0 * M_PI * toneSet[j])/(double)sampleRate);
     }
 }