[RTTY] Added support for ITA2 encoding

examples/SX127x_RTTY_Transmit/SX127x_RTTY_Transmit.ino

@@ -92,6 +92,20 @@ void loop() {
   float f = -3.1415;
   rtty.println(f, 3);
 
+  /*
+    // KiteLib also provides ITA2 ("Baudot") code support
+    // RTTY client must be configured to 5 bits
+    rtty.begin(434, 183, 45, 5);
+
+    // create ITA2-encoded string
+    // NOTE: ASCII characters that do not have ITA2
+    //       equivalent will be replaced with NUL
+    ITA2 itaStr = "HELLO WORLD\n";
+
+    // send the ITA2 string
+    rtty.write(itaStr.byteArr(), itaStr.length());  
+  */
+  
   // turn transmitter off
   fsk.standby();
 

keywords.txt

@@ -27,6 +27,7 @@ XBeeSerial	KEYWORD1
 MQTTClient	KEYWORD1
 HTTPClient	KEYWORD1
 RTTYClient	KEYWORD1
+ITA2	KEYWORD1
 
 #######################################
 # Methods and Functions (KEYWORD2)
@@ -96,6 +97,7 @@ check	KEYWORD2
 
 # RTTY
 idle	KEYWORD2
+byteArr	KEYWORD2
 
 # TransportLayer
 openTransportConnection	KEYWORD2

src/protocols/RTTY.cpp

@@ -1,5 +1,62 @@
 #include "RTTY.h"
 
+ITA2::ITA2(const char* str) {
+  _len = strlen(str);
+  _str = new char[_len];
+  strcpy(_str, str);
+}
+
+ITA2::~ITA2() {
+  delete[] _str;
+}
+
+size_t ITA2::length() {
+  return(_len);
+}
+
+uint8_t* ITA2::byteArr() {
+  // create temporary array 3x the string length (figures may be 3 bytes)
+  uint8_t* temp = new uint8_t[_len*3];
+  
+  size_t arrayLen = 0;
+  for(size_t i = 0; i < _len; i++) {
+    uint16_t code = getBits(_str[i]);
+    // check if the code is letter or figure
+    if(code & (ITA2_FIGS << 10)) {
+      temp[arrayLen] = ITA2_FIGS;
+      temp[arrayLen + 1] = (code >> 5) & ITA2_LTRS;
+      temp[arrayLen + 2] = ITA2_LTRS;
+      arrayLen += 3;
+    } else {
+      temp[arrayLen] = code;
+      arrayLen += 1;
+    }
+  }
+  
+  uint8_t* arr = new uint8_t[arrayLen];
+  memcpy(arr, temp, arrayLen);
+  delete[] temp;
+  return(arr);
+}
+
+uint16_t ITA2::getBits(char c) {
+  // search ITA2 table
+  uint16_t code = 0x0000;
+  for(uint8_t i = 0; i < ITA2_LENGTH; i++) {
+    if(ITA2Table[i][0] == c) {
+      // character is in letter shift
+      code = i;
+      break;
+    } else if(ITA2Table[i][1] == c) {
+      // character is in figures shift
+      code = (ITA2_FIGS << 10) | (i << 5) | ITA2_LTRS;
+      break;
+    }
+  }
+  
+  return(code);
+}
+
 RTTYClient::RTTYClient(PhysicalLayer* phy) {
   _phy = phy;
 }
@@ -68,11 +125,11 @@ size_t RTTYClient::write(uint8_t b) {
 }
 
 size_t RTTYClient::print(const String& str) {
-  return(RTTYClient::write(str.c_str(), str.length()));
+  return(RTTYClient::write((uint8_t*)str.c_str(), str.length()));
 }
 
 size_t RTTYClient::print(const char str[]) {
-  return(RTTYClient::write(str, strlen(str)));
+  return(RTTYClient::write((uint8_t*)str, strlen(str)));
 }
 
 size_t RTTYClient::print(char c) {

src/protocols/RTTY.h

@@ -4,6 +4,33 @@
 #include "TypeDef.h"
 #include "PhysicalLayer.h"
 
+#define ITA2_FIGS                                     0x1B
+#define ITA2_LTRS                                     0x1F
+#define ITA2_LENGTH                                   32
+
+// ITA2 character table: - position in array corresponds to 5-bit ITA2 code
+//                       - characters to the left are in letters shift, characters to the right in figures shift
+//                       - characters marked 0x7F do not have ASCII equivalent
+const char ITA2Table[ITA2_LENGTH][2] = {{'\0', '\0'}, {'E', '3'}, {'\n', '\n'}, {'A', '-'}, {' ', ' '}, {'S', '\''}, {'I', '8'}, {'U', '7'}, 
+                                        {'\r', '\r'}, {'D', 0x05}, {'R', '4'}, {'J', '\a'}, {'N', ','}, {'F', '!'}, {'C', ':'}, {'K', '('}, 
+                                        {'T', '5'}, {'Z', '+'}, {'L', ')'}, {'W', '2'}, {'H', 0x7F}, {'Y', '6'}, {'P', '0'}, {'Q', '1'}, 
+                                        {'O', '9'}, {'B', '?'}, {'G', '&'}, {0x7F, 0x7F}, {'M', '.'}, {'X', '/'}, {'V', ';'}, {0x7F, 0x7F}};
+
+class ITA2 {
+  public:
+    ITA2(const char* str);
+    ~ITA2();
+    
+    size_t length();
+    uint8_t* byteArr();
+  
+  private:
+    char* _str;
+    size_t _len;
+    
+    uint16_t getBits(char c);
+};
+
 class RTTYClient {
   public:
     RTTYClient(PhysicalLayer* phy);