[Hell] Added method to invert text color (#529)

examples/Hellschreiber/Hellschreiber_Transmit_AFSK/Hellschreiber_Transmit_AFSK.ino

@@ -90,6 +90,12 @@ void loop() {
   // string saved in flash
   hell.print(F("Flash String"));
 
+  // in AFSK mode, it is possible to invert the text colors
+  // use white text on black background
+  hell.setInversion(true);
+  hell.print("Inverted String");
+  hell.setInversion(false);
+
   // character
   hell.print('c');
 

keywords.txt

@@ -223,6 +223,7 @@ getRangingResult	KEYWORD2
 
 # Hellschreiber
 printGlyph	KEYWORD2
+setInversion	KEYWORD2
 
 # AFSK
 tone	KEYWORD2

src/protocols/Hellschreiber/Hellschreiber.cpp

@@ -49,6 +49,10 @@ size_t HellClient::printGlyph(uint8_t* buff) {
   return(1);
 }
 
+void HellClient::setInversion(bool invert) {
+  _inv = invert;
+}
+
 size_t HellClient::write(const char* str) {
   if(str == NULL) {
     return(0);
@@ -295,7 +299,7 @@ int16_t HellClient::transmitDirect(uint32_t freq, uint32_t freqHz) {
 int16_t HellClient::standby() {
   #if !defined(RADIOLIB_EXCLUDE_AFSK)
   if(_audio != nullptr) {
-    return(_audio->noTone());
+    return(_audio->noTone(_inv));
   }
   #endif
   return(_phy->standby());

src/protocols/Hellschreiber/Hellschreiber.h

@@ -119,9 +119,18 @@ class HellClient {
       \brief Method to "print" a buffer of pixels, this is exposed to allow users to send custom characters.
 
       \param buff Buffer of pixels to send, in a 7x7 pixel array.
+
+      \returns Always returns the number of printed glyphs (1).
     */
     size_t printGlyph(uint8_t* buff);
 
+    /*!
+      \brief Invert text color.
+
+      \param invert Whether to enable color inversion (white text on black background), or not (black text on white background)
+    */
+    void setInversion(bool invert);
+
     size_t write(const char* str);
     size_t write(uint8_t* buff, size_t len);
     size_t write(uint8_t b);
@@ -159,6 +168,7 @@ class HellClient {
 
     uint32_t _base = 0, _baseHz = 0;
     uint32_t _pixelDuration = 0;
+    bool _inv = false;
 
     size_t printNumber(unsigned long, uint8_t);
     size_t printFloat(double, uint8_t);