From 2de09e1b0a33f6b74b154339290511a2728feeb8 Mon Sep 17 00:00:00 2001
From: Mark Jessop <vk5qi@rfhead.net>
Date: Mon, 31 May 2021 21:16:38 +0930
Subject: [PATCH] Added FSK4 protocol, compatible with Horus Binary 4FSK
 modulation

---
 src/RadioLib.h              |   1 +
 src/protocols/FSK4/FSK4.cpp | 119 ++++++++++++++++++++++++++++++++++++
 src/protocols/FSK4/FSK4.h   |  82 +++++++++++++++++++++++++
 3 files changed, 202 insertions(+)
 create mode 100644 src/protocols/FSK4/FSK4.cpp
 create mode 100644 src/protocols/FSK4/FSK4.h

diff --git a/src/RadioLib.h b/src/RadioLib.h
index edeb8fd6..41784f5c 100644
--- a/src/RadioLib.h
+++ b/src/RadioLib.h
@@ -97,6 +97,7 @@
 #include "protocols/Morse/Morse.h"
 #include "protocols/RTTY/RTTY.h"
 #include "protocols/SSTV/SSTV.h"
+#include "protocols/FSK4/FSK4.h"
 
 // transport layer protocols
 #include "protocols/TransportLayer/TransportLayer.h"
diff --git a/src/protocols/FSK4/FSK4.cpp b/src/protocols/FSK4/FSK4.cpp
new file mode 100644
index 00000000..df331d9c
--- /dev/null
+++ b/src/protocols/FSK4/FSK4.cpp
@@ -0,0 +1,119 @@
+#include "FSK4.h"
+#if !defined(RADIOLIB_EXCLUDE_FSK4)
+
+
+
+FSK4Client::FSK4Client(PhysicalLayer* phy) {
+  _phy = phy;
+  #if !defined(RADIOLIB_EXCLUDE_AFSK)
+  _audio = nullptr;
+  #endif
+}
+
+//#if !defined(RADIOLIB_EXCLUDE_AFSK)
+// FSK4Client::FSK4Client(AFSKClient* audio) {
+//   _phy = audio->_phy;
+//   _audio = audio;
+// }
+//#endif
+
+int16_t FSK4Client::begin(float base, uint32_t shift, uint16_t rate) {
+  // save configuration
+  _baseHz = base;
+  _shiftHz = shift;
+
+
+  // calculate duration of 1 bit
+  _bitDuration = (uint32_t)1000000/rate;
+
+  // calculate module carrier frequency resolution
+  uint32_t step = round(_phy->getFreqStep());
+
+  // check minimum shift value
+  if(shift < step / 2) {
+    return(ERR_INVALID_RTTY_SHIFT);
+  }
+
+  // round shift to multiples of frequency step size
+  if(shift % step < (step / 2)) {
+    _shift = shift / step;
+  } else {
+    _shift = (shift / step) + 1;
+  }
+
+  // Write resultant tones into arrays for quick lookup when modulating.
+  _tones[0] = 0;
+  _tones[1] = _shift;
+  _tones[2] = _shift*2;
+  _tones[3] = _shift*3;
+
+  _tonesHz[0] = 0;
+  _tonesHz[1] = _shiftHz;
+  _tonesHz[2] = _shiftHz*2;
+  _tonesHz[3] = _shiftHz*3;
+
+  // calculate 24-bit frequency
+  _base = (base * 1000000.0) / _phy->getFreqStep();
+
+  // configure for direct mode
+  return(_phy->startDirect());
+}
+
+void FSK4Client::idle() {
+  // Idle at Tone 0.
+  tone(0);
+}
+
+size_t FSK4Client::write(uint8_t* buff, size_t len) {
+  size_t n = 0;
+  for(size_t i = 0; i < len; i++) {
+    n += FSK4Client::write(buff[i]);
+  }
+  FSK4Client::standby();
+  return(n);
+}
+
+size_t FSK4Client::write(uint8_t b) {
+
+    int k;
+    // Send symbols MSB first.
+    for (k=0;k<4;k++)
+    {
+        // Extract 4FSK symbol (2 bits)
+        uint8_t symbol = (b & 0xC0) >> 6;
+        // Modulate
+        FSK4Client::tone(symbol);
+        // Shift to next symbol.
+        b = b << 2;
+    }
+
+  return(1);
+}
+
+void FSK4Client::tone(uint8_t i) {
+  uint32_t start = Module::micros();
+  transmitDirect(_base + _tones[i], _baseHz + _tonesHz[i]);
+  while(Module::micros() - start < _bitDuration) {
+    Module::yield();
+  }
+}
+
+int16_t FSK4Client::transmitDirect(uint32_t freq, uint32_t freqHz) {
+  #if !defined(RADIOLIB_EXCLUDE_AFSK)
+  if(_audio != nullptr) {
+    return(_audio->tone(freqHz));
+  }
+  #endif
+  return(_phy->transmitDirect(freq));
+}
+
+int16_t FSK4Client::standby() {
+  #if !defined(RADIOLIB_EXCLUDE_AFSK)
+  if(_audio != nullptr) {
+    return(_audio->noTone());
+  }
+  #endif
+  return(_phy->standby());
+}
+
+#endif
diff --git a/src/protocols/FSK4/FSK4.h b/src/protocols/FSK4/FSK4.h
new file mode 100644
index 00000000..eb83c66e
--- /dev/null
+++ b/src/protocols/FSK4/FSK4.h
@@ -0,0 +1,82 @@
+#if !defined(_RADIOLIB_FSK4_H)
+#define _RADIOLIB_FSK4_H
+
+#include "../../TypeDef.h"
+
+#if !defined(RADIOLIB_EXCLUDE_FSK4)
+
+#include "../PhysicalLayer/PhysicalLayer.h"
+#include "../AFSK/AFSK.h"
+
+
+/*!
+  \class FSK4Client
+
+  \brief Client for FSK-4 communication. The public interface is the same as Arduino Serial.
+*/
+class FSK4Client {
+  public:
+    /*!
+      \brief Constructor for FSK-4 mode.
+
+      \param phy Pointer to the wireless module providing PhysicalLayer communication.
+    */
+    explicit FSK4Client(PhysicalLayer* phy);
+
+    #if !defined(RADIOLIB_EXCLUDE_AFSK)
+    /*!
+      \brief Constructor for AFSK mode.
+
+      \param audio Pointer to the AFSK instance providing audio.
+    */
+    //explicit FSK4Client(AFSKClient* audio);
+    #endif
+
+    // basic methods
+
+    /*!
+      \brief Initialization method.
+
+      \param base Base (space) frequency to be used in MHz (in FSK-4 mode), or the space tone frequency in Hz (in AFSK mode)
+
+      \param shift Frequency shift between each tone in Hz.
+
+      \param rate Baud rate to be used during transmission.
+
+
+      \returns \ref status_codes
+    */
+    int16_t begin(float base, uint32_t shift, uint16_t rate);
+
+    /*!
+      \brief Send out idle condition (RF tone at mark frequency).
+    */
+    void idle();
+
+    size_t write(uint8_t* buff, size_t len);
+    size_t write(uint8_t b);
+
+
+#ifndef RADIOLIB_GODMODE
+  private:
+#endif
+    PhysicalLayer* _phy;
+    #if !defined(RADIOLIB_EXCLUDE_AFSK)
+    AFSKClient* _audio;
+    #endif
+
+    uint32_t _base = 0, _baseHz = 0;
+    uint32_t _shift = 0, _shiftHz = 0;
+    uint32_t _bitDuration = 0;
+    uint32_t _tones[4];
+    uint32_t _tonesHz[4];
+
+    void tone(uint8_t i);
+
+    int16_t transmitDirect(uint32_t freq = 0, uint32_t freqHz = 0);
+    int16_t standby();
+};
+
+#endif
+
+#endif