[AX25] Added AFSK support

examples/AX25/AX25_Frames/AX25_Frames.ino

@@ -19,6 +19,9 @@
    Frames shown in this example are not
    exhaustive; all possible AX.25 frames
    should be supported.
+
+   For full API reference, see the GitHub Pages
+   https://jgromes.github.io/RadioLib/
 */
 
 // include the library

examples/AX25/AX25_Transmit/AX25_Transmit.ino

@@ -12,6 +12,9 @@
     - SX126x
     - nRF24
     - Si443x/RFM2x
+
+   For full API reference, see the GitHub Pages
+   https://jgromes.github.io/RadioLib/
 */
 
 // include the library
@@ -37,8 +40,8 @@ void setup() {
   // initialize SX1278
   Serial.print(F("[SX1278] Initializing ... "));
   // carrier frequency:           434.0 MHz
-  // bit rate:                    1.2 kbps (1200 baud AFSK AX.25)
+  // bit rate:                    1.2 kbps (1200 baud 2-FSK AX.25)
-  // frequency deviation:         0.5 kHz  (1200 baud AFSK AX.25)
+  // frequency deviation:         0.5 kHz  (1200 baud 2-FSK AX.25)
   int state = fsk.beginFSK(434.0, 1.2, 0.5);
 
   // when using one of the non-LoRa modules for AX.25

examples/AX25/AX25_Transmit_AFSK/AX25_Transmit_AFSK.ino

@@ -0,0 +1,100 @@
+/*
+   RadioLib AX.25 Transmit AFSK Example
+
+   This example sends AX.25 messages using
+   SX1278's FSK modem. The data is modulated
+   as AFSK at 1200 baud using Bell 202 tones.
+
+   Other modules that can be used for AX.25
+   with AFSK modulation:
+    - SX127x/RFM9x
+    - RF69
+    - SX1231
+    - CC1101
+    - nRF24
+    - Si443x/RFM2x
+
+   For full API reference, see the GitHub Pages
+   https://jgromes.github.io/RadioLib/
+*/
+
+// include the library
+#include <RadioLib.h>
+
+// SX1278 has the following connections:
+// NSS pin:   10
+// DIO0 pin:  2
+// RESET pin: 9
+// DIO1 pin:  3
+SX1278 fsk = new Module(10, 2, 9, 3);
+
+// or using RadioShield
+// https://github.com/jgromes/RadioShield
+//SX1278 fsk = RadioShield.ModuleA;
+
+// create AFSK client instance using the FSK module
+// pin 5 is connected to SX1278 DIO2
+AFSKClient audio(&fsk, 5);
+
+// create AX.25 client instance using the AFSK instance
+AX25Client ax25(&audio);
+
+void setup() {
+  Serial.begin(9600);
+
+  // initialize SX1278
+  Serial.print(F("[SX1278] Initializing ... "));
+  // carrier frequency:           434.0 MHz
+  // bit rate:                    48.0 kbps
+  // frequency deviation:         50.0 kHz
+  // Rx bandwidth:                125.0 kHz
+  // output power:                13 dBm
+  // current limit:               100 mA
+  int state = fsk.beginFSK(434.0);
+
+  // when using one of the non-LoRa modules for AX.25
+  // (RF69, CC1101,, Si4432 etc.), use the basic begin() method
+  // int state = fsk.begin();
+
+  if(state == ERR_NONE) {
+    Serial.println(F("success!"));
+  } else {
+    Serial.print(F("failed, code "));
+    Serial.println(state);
+    while(true);
+  }
+
+  // initialize AX.25 client
+  Serial.print(F("[AX.25] Initializing ... "));
+  // source station callsign:     "N7LEM"
+  // source station SSID:         0
+  // preamble length:             8 bytes
+  state = ax25.begin("N7LEM");
+  if(state == ERR_NONE) {
+    Serial.println(F("success!"));
+  } else {
+    Serial.print(F("failed, code "));
+    Serial.println(state);
+    while(true);
+  }
+}
+
+void loop() {
+  // send AX.25 unnumbered information frame
+  Serial.print(F("[AX.25] Sending UI frame ... "));
+  // destination station callsign:     "NJ7P"
+  // destination station SSID:         0
+  int state = ax25.transmit("Hello World!", "NJ7P");
+  if (state == ERR_NONE) {
+    // the packet was successfully transmitted
+    Serial.println(F("success!"));
+
+  } else {
+    // some error occurred
+    Serial.print(F("failed, code "));
+    Serial.println(state);
+
+  }
+
+  delay(1000);
+}

src/protocols/AX25/AX25.cpp

@@ -112,6 +112,12 @@ void AX25Frame::setSendSequence(uint8_t seqNumber) {
 
 AX25Client::AX25Client(PhysicalLayer* phy) {
   _phy = phy;
+  _audio = nullptr;
+}
+
+AX25Client::AX25Client(AFSKClient* audio) {
+  _phy = audio->_phy;
+  _audio = audio;
 }
 
 int16_t AX25Client::begin(const char* srcCallsign, uint8_t srcSSID, uint8_t preambleLen) {
@@ -130,11 +136,14 @@ int16_t AX25Client::begin(const char* srcCallsign, uint8_t srcSSID, uint8_t prea
   // save preamble length
   _preambleLen = preambleLen;
 
-  // disable physical layer data shaping and set encoding to NRZ
+  // set module frequency deviation to 0 if using FSK
-  int16_t state = _phy->setDataShaping(0.0);
+  int16_t state = ERR_NONE;
-  RADIOLIB_ASSERT(state);
+  if(_audio == nullptr) {
+    state = _phy->setFrequencyDeviation(0);
+    RADIOLIB_ASSERT(state);
 
-  state = _phy->setEncoding(0);
+    state = _phy->setEncoding(0);
+  }
   return(state);
 }
 
@@ -154,7 +163,7 @@ int16_t AX25Client::sendFrame(AX25Frame* frame) {
   if(strlen(frame->destCallsign) > AX25_MAX_CALLSIGN_LEN) {
     return(ERR_INVALID_CALLSIGN);
   }
-  
+
   // check repeater configuration
   #ifndef RADIOLIB_STATIC_ONLY
     if(!(((frame->repeaterCallsigns == NULL) && (frame->repeaterSSIDs == NULL) && (frame->numRepeaters == 0)) ||
@@ -333,7 +342,32 @@ int16_t AX25Client::sendFrame(AX25Frame* frame) {
   }
 
   // transmit
-  int16_t state = _phy->transmit(stuffedFrameBuff, stuffedFrameBuffLen);
+  int16_t state = ERR_NONE;
+  if(_audio == nullptr) {
+    state = _phy->transmit(stuffedFrameBuff, stuffedFrameBuffLen);
+  } else {
+    _phy->transmitDirect();
+
+    // iterate over all bytes in the buffer
+    for(uint32_t i = 0; i < stuffedFrameBuffLen; i++) {
+
+      // check each bit
+      for(uint16_t mask = 0x80; mask >= 0x01; mask >>= 1) {
+        uint32_t start = micros();
+        if(stuffedFrameBuff[i] & mask) {
+          _audio->tone(AX25_AFSK_MARK, false);
+        } else {
+          _audio->tone(AX25_AFSK_SPACE, false);
+        }
+        while(micros() - start < 833) {
+          yield();
+        }
+      }
+
+    }
+
+    _audio->noTone();
+  }
 
   // deallocate memory
   #ifndef RADIOLIB_STATIC_ONLY

src/protocols/AX25/AX25.h

@@ -3,6 +3,7 @@
 
 #include "../../TypeDef.h"
 #include "../PhysicalLayer/PhysicalLayer.h"
+#include "../AFSK/AFSK.h"
 
 // macros to access bits in byte array, from http://www.mathcs.emory.edu/~cheung/Courses/255/Syllabus/1-C-intro/bit-array.html
 #define SET_BIT_IN_ARRAY(A, k)                        ( A[(k/8)] |= (1 << (k%8)) )
@@ -69,6 +70,13 @@
 #define AX25_PID_NO_LAYER_3                           0xF0
 #define AX25_PID_ESCAPE_CHARACTER                     0xFF
 
+// AFSK tones in Hz
+#define AX25_AFSK_MARK                                1200
+#define AX25_AFSK_SPACE                               2200
+
+// tone duration in us (for 1200 baud AFSK)
+#define AX25_AFSK_TONE_DURATION                       833
+
 /*!
   \class AX25Frame
 
@@ -254,12 +262,19 @@ class AX25Frame {
 class AX25Client {
   public:
     /*!
-      \brief Default constructor.
+      \brief Constructor for 2-FSK mode.
 
       \param phy Pointer to the wireless module providing PhysicalLayer communication.
     */
     AX25Client(PhysicalLayer* phy);
 
+    /*!
+      \brief Constructor for AFSK mode.
+
+      \param audio Pointer to the AFSK instance providing audio.
+    */
+    AX25Client(AFSKClient* audio);
+
     // basic methods
 
     /*!
@@ -301,6 +316,7 @@ class AX25Client {
   private:
 #endif
     PhysicalLayer* _phy;
+    AFSKClient* _audio;
 
     char _srcCallsign[AX25_MAX_CALLSIGN_LEN + 1];
     uint8_t _srcSSID;