NFM mod: implemented Digital Code Squelch (DCS)

plugins/channeltx/modnfm/CMakeLists.txt

@@ -3,6 +3,7 @@ project(modnfm)
 set(modnfm_SOURCES
     nfmmod.cpp
     nfmmodbaseband.cpp
+    nfmmoddcs.cpp
     nfmmodsource.cpp
 	nfmmodplugin.cpp
     nfmmodsettings.cpp
@@ -12,6 +13,7 @@ set(modnfm_SOURCES
 set(modnfm_HEADERS
 	nfmmod.h
     nfmmodbaseband.h
+    nfmmoddcs.h
     nfmmodsource.h
 	nfmmodplugin.h
     nfmmodsettings.h

plugins/channeltx/modnfm/nfmmod.cpp

@@ -260,6 +260,9 @@ void NFMMod::applySettings(const NFMModSettings& settings, bool force)
             << " m_toneFrequency: " << settings.m_toneFrequency
             << " m_ctcssIndex: " << settings.m_ctcssIndex
             << " m_ctcssOn: " << settings.m_ctcssOn
+            << " m_dcsOn: " << settings.m_dcsOn
+            << " m_dcsCode: " << settings.m_dcsCode
+            << " m_dcsPositive: " << settings.m_dcsPositive
             << " m_channelMute: " << settings.m_channelMute
             << " m_playLoop: " << settings.m_playLoop
             << " m_modAFInput " << settings.m_modAFInput

plugins/channeltx/modnfm/nfmmoddcs.cpp

@@ -0,0 +1,97 @@
+///////////////////////////////////////////////////////////////////////////////////
+// Copyright (C) 2021 Edouard Griffiths, F4EXB                                   //
+//                                                                               //
+// 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/>.          //
+//                                                                               //
+// Source: https://mmi-comm.tripod.com/dcs.html                                  //
+///////////////////////////////////////////////////////////////////////////////////
+
+#include <bitset>
+
+#include "nfmmoddcs.h"
+
+const float NFMModDCS::m_codeRate = 134.3; //!< bits per second
+
+NFMModDCS::NFMModDCS()
+{
+    reset();
+}
+
+NFMModDCS::~NFMModDCS()
+{
+}
+
+void NFMModDCS::reset()
+{
+    m_step = 0;
+}
+
+void NFMModDCS::setDCS(int code)
+{
+    unsigned int dcsCode = code < 0 ? 0 : code > 511 ? 511 : code; // trim invalid values
+    // Parity bits calculation:
+    unsigned int p[11];
+    p[0]  = std::bitset<32>(dcsCode & 0b10011111).count() % 2;      // P0  = C0 + C1 + C2 + C3 + C4 + C7 (modulo two addition)
+    p[1]  = (std::bitset<32>(dcsCode & 0b100111110).count()+1) % 2; // P1  = NOT ( C1 + C2 + C3 + C4 + C5 + C8 )
+    p[2]  = std::bitset<32>(dcsCode & 0b11100011).count() % 2;      // P2  = C0 + C1 + C5 + C6 + C7
+    p[3]  = (std::bitset<32>(dcsCode & 0b111000110).count()+1) % 2; // P3  = NOT ( C1 + C2 + C6 + C7 + C8 )
+    p[4]  = (std::bitset<32>(dcsCode & 0b100010011).count()+1) % 2; // P4  = NOT ( C0 + C1 + C4 + C8 )
+    p[5]  = (std::bitset<32>(dcsCode & 0b10111001).count()+1) % 2;  // P5  = NOT ( C0 + C3 + C4 + C5 + C7 )
+    p[6]  = std::bitset<32>(dcsCode & 0b111101101).count() % 2;     // P6  = C0 + C2 + C3 + C5 + C6 + C7 + C8
+    p[7]  = std::bitset<32>(dcsCode & 0b111011010).count() % 2;     // P7  = C1 + C3 + C4 + C6 + C7 + C8
+    p[8]  = std::bitset<32>(dcsCode & 0b110110100).count() % 2;     // P8  = C2 + C4 + C5 + C7 + C8
+    p[9]  = (std::bitset<32>(dcsCode & 0b101101000).count()+1) % 2; // P9  = NOT ( C3 + C5 + C6 + C8 )
+    p[10] = (std::bitset<32>(dcsCode & 0b1001111).count()+1) % 2;   // P10 = NOT ( C0 + C1 + C2 + C3 + C6 )
+    int dcsIndex = 0;
+    // code:
+    for (int i = 0; i < 9; i++, dcsIndex++) {
+        m_dcsWord[dcsIndex] = (dcsCode >> i) & 1;
+    }
+    // filler (0x04)
+    m_dcsWord[dcsIndex++] = 0;
+    m_dcsWord[dcsIndex++] = 0;
+    m_dcsWord[dcsIndex++] = 1;
+    // parity
+    for (int i = 0; i < 11; i++, dcsIndex++) {
+        m_dcsWord[dcsIndex] = p[i];
+    }
+
+    m_step = 0;
+}
+
+void NFMModDCS::setPositive(bool positive)
+{
+    m_positive = positive;
+    m_step = 0;
+}
+
+void NFMModDCS::setSampleRate(int sampleRate)
+{
+    m_bitPerStep = m_codeRate / sampleRate;
+    m_step = 0;
+}
+
+int NFMModDCS::next()
+{
+    int dcsIndex = (int) m_step;
+    int carrier = (m_dcsWord[dcsIndex] == 1) ? (m_positive ? 1 : -1) : (m_positive ? -1 : 1);
+
+    if (m_step + m_bitPerStep < 23) {
+        m_step += m_bitPerStep;
+    } else {
+        m_step = m_step + m_bitPerStep - 23;
+    }
+
+    return carrier;
+}

plugins/channeltx/modnfm/nfmmoddcs.h

@@ -0,0 +1,43 @@
+///////////////////////////////////////////////////////////////////////////////////
+// Copyright (C) 2021 Edouard Griffiths, F4EXB                                   //
+//                                                                               //
+// 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/>.          //
+///////////////////////////////////////////////////////////////////////////////////
+
+#ifndef PLUGINS_CHANNELTX_MODNFM_NFMMODDCS_H_
+#define PLUGINS_CHANNELTX_MODNFM_NFMMODDCS_H_
+
+class NFMModDCS
+{
+public:
+    NFMModDCS();
+    ~NFMModDCS();
+
+    void reset();
+    void setDCS(int code);
+    void setPositive(bool positive);
+    void setSampleRate(int sampleRate);
+    int next(); //!< +1/-1 sample
+
+private:
+    int m_shift; //!< current frequency shift: -1 or 1
+    int m_dcsWord[23]; //!< current DCS word in transmit order including parity and filler 11 + 3 + 9
+    float m_step;
+    bool m_positive;
+    float m_bitPerStep;
+    static const float m_codeRate;
+};
+
+
+#endif // PLUGINS_CHANNELTX_MODNFM_NFMMODDCS_H_

plugins/channeltx/modnfm/nfmmodgui.cpp

@@ -20,6 +20,7 @@
 #include <QFileDialog>
 #include <QTime>
 #include <QDebug>
+#include <QRegExp>
 
 #include "device/deviceuiset.h"
 #include "plugin/pluginapi.h"
@@ -299,10 +300,35 @@ void NFMModGUI::on_ctcss_currentIndexChanged(int index)
 
 void NFMModGUI::on_ctcssOn_toggled(bool checked)
 {
+    ui->dcsOn->setEnabled(!checked);
     m_settings.m_ctcssOn = checked;
     applySettings();
 }
 
+void NFMModGUI::on_dcsOn_toggled(bool checked)
+{
+    ui->ctcssOn->setEnabled(!checked);
+    m_settings.m_dcsOn = checked;
+    applySettings();
+}
+
+void NFMModGUI::on_dcsCode_editingFinished()
+{
+    bool ok;
+    int dcsCode = ui->dcsCode->text().toInt(&ok, 8);
+
+    if (ok)
+    {
+        m_settings.m_dcsCode = dcsCode;
+        applySettings();
+    }
+}
+
+void NFMModGUI::on_dcsPositive_toggled(bool checked)
+{
+    m_settings.m_dcsPositive = checked;
+    applySettings();
+}
 
 void NFMModGUI::configureFileName()
 {
@@ -375,7 +401,8 @@ NFMModGUI::NFMModGUI(PluginAPI* pluginAPI, DeviceUISet *deviceUISet, BasebandSam
     m_audioSampleRate(-1),
     m_feedbackAudioSampleRate(-1),
     m_tickCount(0),
-    m_enableNavTime(false)
+    m_enableNavTime(false),
+    m_dcsCodeValidator(QRegExp("[0-7]{1,3}"))
 {
 	ui->setupUi(this);
 	setAttribute(Qt::WA_DeleteOnClose, true);
@@ -431,6 +458,7 @@ NFMModGUI::NFMModGUI(PluginAPI* pluginAPI, DeviceUISet *deviceUISet, BasebandSam
         ui->ctcss->addItem(QString("%1").arg((double) NFMModSettings::getCTCSSFreq(i), 0, 'f', 1));
     }
 
+    ui->dcsCode->setValidator(&m_dcsCodeValidator);
     ui->cwKeyerGUI->setCWKeyer(m_nfmMod->getCWKeyer());
 
 	connect(getInputMessageQueue(), SIGNAL(messageEnqueued()), this, SLOT(handleSourceMessages()));
@@ -500,6 +528,11 @@ void NFMModGUI::displaySettings()
     ui->ctcssOn->setChecked(m_settings.m_ctcssOn);
     ui->ctcss->setCurrentIndex(m_settings.m_ctcssIndex);
 
+    ui->dcsOn->setChecked(m_settings.m_dcsOn);
+    ui->dcsOn->setEnabled(!m_settings.m_ctcssOn);
+    ui->dcsCode->setText(tr("%1").arg(m_settings.m_dcsCode, 3, 8, QLatin1Char('0')));
+    ui->dcsPositive->setChecked(m_settings.m_dcsPositive);
+
     ui->channelMute->setChecked(m_settings.m_channelMute);
     ui->playLoop->setChecked(m_settings.m_playLoop);
 

plugins/channeltx/modnfm/nfmmodgui.h

@@ -18,6 +18,8 @@
 #ifndef PLUGINS_CHANNELTX_MODNFM_NFMMODGUI_H_
 #define PLUGINS_CHANNELTX_MODNFM_NFMMODGUI_H_
 
+#include <QRegExpValidator>
+
 #include "channel/channelgui.h"
 #include "dsp/channelmarker.h"
 #include "util/movingaverage.h"
@@ -70,6 +72,7 @@ private:
     bool m_enableNavTime;
     NFMModSettings::NFMModInputAF m_modAFInput;
     MessageQueue m_inputMessageQueue;
+    QRegExpValidator m_dcsCodeValidator;
 
     explicit NFMModGUI(PluginAPI* pluginAPI, DeviceUISet *deviceUISet, BasebandSampleSource *channelTx, QWidget* parent = 0);
     virtual ~NFMModGUI();
@@ -107,6 +110,9 @@ private slots:
 
     void on_ctcss_currentIndexChanged(int index);
     void on_ctcssOn_toggled(bool checked);
+    void on_dcsOn_toggled(bool checked);
+    void on_dcsCode_editingFinished();
+    void on_dcsPositive_toggled(bool checked);
 
     void on_feedbackEnable_toggled(bool checked);
     void on_feedbackVolume_valueChanged(int value);

plugins/channeltx/modnfm/nfmmodgui.ui

@@ -673,6 +673,67 @@
         </property>
        </widget>
       </item>
+      <item>
+       <widget class="QLabel" name="dcsLabel">
+        <property name="text">
+         <string>DCS</string>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QCheckBox" name="dcsOn">
+        <property name="toolTip">
+         <string>Activate DCS</string>
+        </property>
+        <property name="text">
+         <string/>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QLineEdit" name="dcsCode">
+        <property name="minimumSize">
+         <size>
+          <width>40</width>
+          <height>0</height>
+         </size>
+        </property>
+        <property name="maximumSize">
+         <size>
+          <width>40</width>
+          <height>16777215</height>
+         </size>
+        </property>
+        <property name="focusPolicy">
+         <enum>Qt::ClickFocus</enum>
+        </property>
+        <property name="acceptDrops">
+         <bool>false</bool>
+        </property>
+        <property name="toolTip">
+         <string>DCS code (octal)</string>
+        </property>
+        <property name="text">
+         <string>023</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QCheckBox" name="dcsPositive">
+        <property name="toolTip">
+         <string>DCS code is positive (1 corresponds to positive frequency shift)</string>
+        </property>
+        <property name="layoutDirection">
+         <enum>Qt::RightToLeft</enum>
+        </property>
+        <property name="text">
+         <string>+</string>
+        </property>
+       </widget>
+      </item>
       <item>
        <spacer name="horizontalSpacer_4">
         <property name="orientation">

plugins/channeltx/modnfm/nfmmodsettings.cpp

@@ -62,6 +62,9 @@ void NFMModSettings::resetToDefaults()
     m_playLoop = false;
     m_ctcssOn = false;
     m_ctcssIndex = 0;
+    m_dcsOn = false;
+    m_dcsCode = 0023;
+    m_dcsPositive = false;
     m_rgbColor = QColor(255, 0, 0).rgb();
     m_title = "NFM Modulator";
     m_modAFInput = NFMModInputAF::NFMModInputNone;
@@ -113,6 +116,9 @@ QByteArray NFMModSettings::serialize() const
     s.writeReal(21, m_feedbackVolumeFactor);
     s.writeBool(22, m_feedbackAudioEnable);
     s.writeS32(23, m_streamIndex);
+    s.writeBool(24, m_dcsOn);
+    s.writeS32(25, m_dcsCode);
+    s.writeBool(26, m_dcsPositive);
 
     return s.final();
 }
@@ -186,6 +192,10 @@ bool NFMModSettings::deserialize(const QByteArray& data)
         d.readReal(21, &m_feedbackVolumeFactor, 1.0);
         d.readBool(22, &m_feedbackAudioEnable, false);
         d.readS32(23, &m_streamIndex, 0);
+        d.readBool(24, &m_dcsOn, false);
+        d.readS32(25, &tmp, 0023);
+        m_dcsCode = tmp < 0 ? 0 : tmp > 511 ? 511 : tmp;
+        d.readBool(26, &m_dcsPositive, false);
 
         return true;
     }

plugins/channeltx/modnfm/nfmmodsettings.h

@@ -51,6 +51,9 @@ struct NFMModSettings
     bool m_playLoop;
     bool m_ctcssOn;
     int  m_ctcssIndex;
+    bool m_dcsOn;
+    int m_dcsCode;
+    bool m_dcsPositive;
     quint32 m_rgbColor;
     QString m_title;
     NFMModInputAF m_modAFInput;

plugins/channeltx/modnfm/nfmmodsource.cpp

@@ -152,6 +152,8 @@ void NFMModSource::modulateSample()
 
     if (m_settings.m_ctcssOn) {
         t1 = (0.85f * m_bandpass.filter(t) + 0.15f * 0.625f * m_ctcssNco.next()) * 1.2f;
+    } else if (m_settings.m_dcsOn) {
+        t1 = (0.9f * m_bandpass.filter(t) + 0.1f * 0.625f * m_dcsMod.next()) * 1.2f;
     } else {
         t1 = m_bandpass.filter(t) * 1.2f;
     }
@@ -344,6 +346,7 @@ void NFMModSource::applyAudioSampleRate(int sampleRate)
     m_bandpass.create(301, sampleRate, 300.0, m_settings.m_afBandwidth);
     m_toneNco.setFreq(m_settings.m_toneFrequency, sampleRate);
     m_ctcssNco.setFreq(NFMModSettings::getCTCSSFreq(m_settings.m_ctcssIndex), sampleRate);
+    m_dcsMod.setSampleRate(sampleRate);
     m_cwKeyer.setSampleRate(sampleRate);
     m_cwKeyer.reset();
     m_preemphasisFilter.configure(m_preemphasis*sampleRate);
@@ -400,6 +403,14 @@ void NFMModSource::applySettings(const NFMModSettings& settings, bool force)
         m_ctcssNco.setFreq(NFMModSettings::getCTCSSFreq(settings.m_ctcssIndex), m_audioSampleRate);
     }
 
+    if ((settings.m_dcsCode != m_settings.m_dcsCode) || force) {
+        m_dcsMod.setDCS(settings.m_dcsCode);
+    }
+
+    if ((settings.m_dcsPositive != m_settings.m_dcsPositive) || force) {
+        m_dcsMod.setPositive(settings.m_dcsPositive);
+    }
+
     if ((settings.m_modAFInput != m_settings.m_modAFInput) || force)
     {
         if (settings.m_modAFInput == NFMModSettings::NFMModInputAudio) {

plugins/channeltx/modnfm/nfmmodsource.h

@@ -36,6 +36,7 @@
 #include "audio/audiofifo.h"
 
 #include "nfmmodsettings.h"
+#include "nfmmoddcs.h"
 
 class ChannelAPI;
 
@@ -78,6 +79,7 @@ private:
     NCO m_carrierNco;
     NCOF m_toneNco;
     NCOF m_ctcssNco;
+    NFMModDCS m_dcsMod;
     float m_modPhasor; //!< baseband modulator phasor
     Complex m_modSample;
 

plugins/channeltx/modnfm/readme.md

@@ -248,3 +248,15 @@ This is the audio file play length in time units
 <h3>23: Play file position slider</h3>
 
 This slider can be used to randomly set the current position in the file when file play is in pause state (button 18.3)
+
+<h3>24: DCS switch</h3>
+
+Checkbox to switch on the DCS (Digital Code Squelch) sub-audio modulation.
+
+<h3>25: DCS code</h3>
+
+This is the DCS octal code (0..511 in decimal 0..777 in octal)
+
+<h3>26: DCS positive modulation</h3>
+
+When checked the "1" bits are represented with positive shift frequency and "0" with negative shift. When unchecked (negative modulation) this is the opposite.