Allow modems to limit/control input rate

- Modems can now over-ride user rate input and lock/step as needed
- Separate digital code defs a bit more so it’s not required when
disabled
- Testing FSK based on @andresv ’s example at
https://github.com/jgaeddert/liquid-dsp/issues/9

src/modules/modem/Modem.h

@@ -44,6 +44,7 @@ public:
     Modem();
     virtual ~Modem();
     
+    virtual int checkSampleRate(long long sampleRate, int audioSampleRate) = 0;
     virtual ModemKit *buildKit(long long sampleRate, int audioSampleRate) = 0;
     virtual void disposeKit(ModemKit *kit) = 0;
     virtual void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) = 0;

src/modules/modem/ModemAnalog.cpp

@@ -8,6 +8,10 @@ std::string ModemAnalog::getType() {
     return "analog";
 }
 
+int ModemAnalog::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    return sampleRate;
+}
+
 ModemKit *ModemAnalog::buildKit(long long sampleRate, int audioSampleRate) {
     ModemKitAnalog *akit = new ModemKitAnalog;
     

src/modules/modem/ModemAnalog.h

@@ -16,12 +16,13 @@ class ModemAnalog : public Modem {
 public:
     ModemAnalog();
     std::string getType();
-    ModemKit *buildKit(long long sampleRate, int audioSampleRate);
-    void disposeKit(ModemKit *kit);
-    void initOutputBuffers(ModemKitAnalog *akit, ModemIQData *input);
-    void buildAudioOutput(ModemKitAnalog *akit, AudioThreadInput *audioOut, bool autoGain);
-    std::vector<float> *getDemodOutputData();
-    std::vector<float> *getResampledOutputData();
+    virtual int checkSampleRate(long long sampleRate, int audioSampleRate);
+    virtual ModemKit *buildKit(long long sampleRate, int audioSampleRate);
+    virtual void disposeKit(ModemKit *kit);
+    virtual void initOutputBuffers(ModemKitAnalog *akit, ModemIQData *input);
+    virtual void buildAudioOutput(ModemKitAnalog *akit, AudioThreadInput *audioOut, bool autoGain);
+    virtual std::vector<float> *getDemodOutputData();
+    virtual std::vector<float> *getResampledOutputData();
 protected:
     int bufSize;
     std::vector<float> demodOutputData;

src/modules/modem/ModemDigital.cpp

@@ -8,6 +8,10 @@ std::string ModemDigital::getType() {
     return "digital";
 }
 
+int ModemDigital::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    return sampleRate;
+}
+
 ModemKit *ModemDigital::buildKit(long long sampleRate, int audioSampleRate) {
     ModemKitDigital *dkit = new ModemKitDigital;
     

src/modules/modem/ModemDigital.h

@@ -13,10 +13,11 @@ class ModemDigital : public Modem {
 public:
     ModemDigital();
     std::string getType();
-    ModemKit *buildKit(long long sampleRate, int audioSampleRate);
-    void disposeKit(ModemKit *kit);
-    void digitalStart(ModemKitDigital *kit, modem mod, ModemIQData *input);
-    void digitalFinish(ModemKitDigital *kit, modem mod);
+    virtual int checkSampleRate(long long sampleRate, int audioSampleRate);
+    virtual ModemKit *buildKit(long long sampleRate, int audioSampleRate);
+    virtual void disposeKit(ModemKit *kit);
+    virtual void digitalStart(ModemKitDigital *kit, modem mod, ModemIQData *input);
+    virtual void digitalFinish(ModemKitDigital *kit, modem mod);
 
     virtual void setDemodulatorLock(bool demod_lock_in);
     virtual int getDemodulatorLock();

src/modules/modem/analog/ModemFMStereo.cpp

@@ -30,6 +30,14 @@ Modem *ModemFMStereo::factory() {
     return new ModemFMStereo;
 }
 
+int ModemFMStereo::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    if (sampleRate < 100000) {
+        return 100000;
+    } else {
+        return sampleRate;
+    }
+}
+
 ModemKit *ModemFMStereo::buildKit(long long sampleRate, int audioSampleRate) {
     ModemKitFMStereo *kit = new ModemKitFMStereo;
     

src/modules/modem/analog/ModemFMStereo.h

@@ -23,6 +23,7 @@ public:
     std::string getType();
     std::string getName();
     Modem *factory();
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     ModemKit *buildKit(long long sampleRate, int audioSampleRate);
     void disposeKit(ModemKit *kit);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);

src/modules/modem/analog/ModemIQ.cpp

@@ -10,6 +10,8 @@ Modem *ModemIQ::factory() {
 
 ModemKit *ModemIQ::buildKit(long long sampleRate, int audioSampleRate) {
     ModemKit *kit = new ModemKit;
+    kit->sampleRate = sampleRate;
+    kit->audioSampleRate = audioSampleRate;
     return kit;
 }
 
@@ -25,6 +27,10 @@ void ModemIQ::disposeKit(ModemKit *kit) {
     delete kit;
 }
 
+int ModemIQ::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    return audioSampleRate;
+}
+
 void ModemIQ::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
     int bufSize = input->data.size();
     

src/modules/modem/analog/ModemIQ.h

@@ -8,6 +8,7 @@ public:
     std::string getName();
     Modem *factory();
     ModemKit *buildKit(long long sampleRate, int audioSampleRate);
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     void disposeKit(ModemKit *kit);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);
     

src/modules/modem/analog/ModemLSB.cpp

@@ -19,6 +19,13 @@ ModemLSB::~ModemLSB() {
     ampmodem_destroy(demodAM_LSB);
 }
 
+int ModemLSB::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    if (sampleRate % 2 == 0) {
+        return sampleRate;
+    }
+    return sampleRate+1;
+}
+
 void ModemLSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
     ModemKitAnalog *akit = (ModemKitAnalog *)kit;
     

src/modules/modem/analog/ModemLSB.h

@@ -8,6 +8,7 @@ public:
     ~ModemLSB();
     std::string getName();
     Modem *factory();
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);
     
 private:

src/modules/modem/analog/ModemUSB.cpp

@@ -19,6 +19,13 @@ ModemUSB::~ModemUSB() {
     ampmodem_destroy(demodAM_USB);
 }
 
+int ModemUSB::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    if (sampleRate % 2 == 0) {
+        return sampleRate;
+    }
+    return sampleRate+1;
+}
+
 void ModemUSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
     ModemKitAnalog *akit = (ModemKitAnalog *)kit;
     

src/modules/modem/analog/ModemUSB.h

@@ -7,6 +7,7 @@ public:
     ~ModemUSB();
     std::string getName();
     Modem *factory();
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);
     
 private:

src/modules/modem/digital/ModemFSK.cpp

@@ -0,0 +1,62 @@
+#include "ModemFSK.h"
+
+ModemFSK::ModemFSK() {
+    demodulatorCons.store(2);
+    currentDemodCons.store(0);
+    updateDemodulatorCons(2);
+}
+
+Modem *ModemFSK::factory() {
+    return new ModemFSK;
+}
+
+ModemKit *ModemFSK::buildKit(long long sampleRate, int audioSampleRate) {
+    ModemKitFSK *dkit = new ModemKitFSK;
+    dkit->m           = 1;
+    dkit->k           = sampleRate / 9600;
+    dkit->bandwidth   = 7000.0 / sampleRate;
+
+    dkit->demodFSK = fskdem_create(dkit->m, dkit->k, dkit->bandwidth);
+
+    dkit->sampleRate = sampleRate;
+    dkit->audioSampleRate = audioSampleRate;
+ 
+    return dkit;
+}
+
+void ModemFSK::disposeKit(ModemKit *kit) {
+    ModemKitFSK *dkit = (ModemKitFSK *)kit;
+    
+    delete dkit;
+}
+
+std::string ModemFSK::getName() {
+    return "FSK";
+}
+
+ModemFSK::~ModemFSK() {
+
+}
+
+void ModemFSK::updateDemodulatorCons(int cons) {
+   
+}
+
+void ModemFSK::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
+    ModemKitFSK *dkit = (ModemKitFSK *)kit;
+    
+    digitalStart(dkit, nullptr, input);
+
+    dkit->inputBuffer.insert(dkit->inputBuffer.end(),input->data.begin(),input->data.end());
+
+    while (dkit->inputBuffer.size() >= dkit->k) {
+        unsigned int sym_out;
+
+        sym_out = fskdem_demodulate(dkit->demodFSK, &dkit->inputBuffer[0]);
+//        std::cout << "ferror: " << fskdem_get_frequency_error(dkit->demodFSK) << std::endl;
+        printf("%01X", sym_out);
+        dkit->inputBuffer.erase(dkit->inputBuffer.begin(),dkit->inputBuffer.begin()+dkit->k);
+    }
+    
+    digitalFinish(dkit, nullptr);
+}

src/modules/modem/digital/ModemFSK.h

@@ -0,0 +1,29 @@
+#pragma once
+#include "ModemDigital.h"
+
+class ModemKitFSK : public ModemKitDigital {
+public:
+    float sps, spacing, bandwidth;
+    unsigned int m, k;
+    
+    fskdem demodFSK;
+    std::vector<liquid_float_complex> inputBuffer;
+};
+
+
+class ModemFSK : public ModemDigital {
+public:
+    ModemFSK();
+    ~ModemFSK();
+    std::string getName();
+    Modem *factory();
+    ModemKit *buildKit(long long sampleRate, int audioSampleRate);
+    void disposeKit(ModemKit *kit);
+    void updateDemodulatorCons(int cons);
+    void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);
+
+
+private:
+    fskdem dem;
+};
+