Implement display character.

README.md

@@ -78,6 +78,28 @@ ___
   void displayText(String text, unsigned long scrollingSpeed);
 ```
 
+___
+
+### Display a character on a 8x8 LED display.
+* @param `index` - The index of the character to be displayed. The value is between 0 (0x00) and 255 (0xFF). You can find the characters corresponding to each index in the section below:
+* @param `scrollingSpeed` - optional - The scrolling speed is between 1.0 (lowest speed) and 100.0 (highest speed). 90.0 is the default value.
+```c++
+  void displayCharacter(int index, unsigned long scrollingSpeed);
+```
+
+#### 8x8 Characters Overview
+![](docs/images/font-8x8-overview.png)
+
+[image source][5]
+
+To know the index of a character we combine the column index with the row index. Both column and row index are hexadecimal values.
+
+For example the heart ❤ (column index: **0x** and row index: **x3**) is at index **0x03**.
+```c++
+  int heartIndex = 0x03;
+  render.displayCharacter(heartIndex); // display a scrolling heart ❤.
+```
+
 ---
 
 ### ScrollingDirection enumeration
@@ -110,3 +132,4 @@ enum CharacterOrientation
 [2]: https://osoyoo.com/2017/07/15/arduino-lesson-8x8-led-matrix
 [3]: https://mega.nz/folder/TI1QgAKQ#DpCOElh-b6mnEuqUMAVcqQ/folder/aAlUDCwZ
 [4]: http://arduino.cc/en/Guide/Libraries
+[5]: http://www.gammon.com.au/forum/?id=11516

ScrollingText8x8Display.cpp

@@ -62,6 +62,23 @@ void ScrollingText8x8Display::setCharacterInBuffer(byte newCharacter[DISPLAY_SIZ
  * @param scrollingSpeed - The scrolling speed is between 1.0 (lowest speed) and 100.0 (highest speed). 90.0 is the default value.
  */
 void ScrollingText8x8Display::displayText(String text, unsigned long scrollingSpeed)
+{
+  int textLength = text.length();
+  for (int i = 0; i < textLength; i++)
+  {
+    int charAsInt = (int)(text.charAt(i));
+
+    displayCharacter(charAsInt, scrollingSpeed);
+  }
+}
+
+/**
+ * Display a character on a 8x8 LED display.
+ *
+ * @param index - The index of the character to be displayed. The value is between 0 (0x00) and 255 (0xFF). You can find the characters corresponding to each index here: https://github.com/TheJLifeX/ScrollingText8x8Display#8x8-characters-overview
+ * @param scrollingSpeed - The scrolling speed is between 1.0 (lowest speed) and 100.0 (highest speed). 90.0 is the default value.
+ */
+void ScrollingText8x8Display::displayCharacter(int index, unsigned long scrollingSpeed)
 {
   float duration = map(
       scrollingSpeed,
@@ -70,24 +87,18 @@ void ScrollingText8x8Display::displayText(String text, unsigned long scrollingSp
       MAXIMAL_DURATION_FOR_ONE_CHARACTER,
       minimalDurationForOneCharacter);
 
-  int textLength = text.length();
-  for (int i = 0; i < textLength; i++)
+  if (index < 0 || index >= NUMBER_OF_CHARACTERS)
   {
-    int charAsInt = (int)(text.charAt(i));
-
-    if (charAsInt < 0 || charAsInt >= NUMBER_OF_CHARACTERS)
-    {
-      charAsInt = UNKNOW_CHARACTER;
-    }
+    index = UNKNOW_CHARACTER;
+  }
 
-    byte asciiCharacter[DISPLAY_SIZE];
-    for (int k = 0; k < DISPLAY_SIZE; k++)
-    {
-      // `pgm_read_byte` function documentation, see: https://www.arduino.cc/reference/en/language/variables/utilities/progmem/
-      asciiCharacter[k] = pgm_read_byte(&(font_8x8[charAsInt][k]));
-    }
-    displayScrolling_8x8_AsciiCharacter(asciiCharacter, duration);
+  byte asciiCharacter[DISPLAY_SIZE];
+  for (int k = 0; k < DISPLAY_SIZE; k++)
+  {
+    // `pgm_read_byte` function documentation, see: https://www.arduino.cc/reference/en/language/variables/utilities/progmem/
+    asciiCharacter[k] = pgm_read_byte(&(font_8x8[index][k]));
   }
+  displayScrolling_8x8_AsciiCharacter(asciiCharacter, duration);
 }
 
 /**

ScrollingText8x8Display.h

@@ -48,6 +48,7 @@ class ScrollingText8x8Display
             ScrollingDirection scrollingDirection = RIGHT_TO_LEFT,
             CharacterOrientation characterOrientation = TOP);
   void displayText(String text, unsigned long scrollingSpeed = DEFAULT_SCROLLING_SPEED);
+  void displayCharacter(int index, unsigned long scrollingSpeed = DEFAULT_SCROLLING_SPEED);
 
 private:
   // Time to wait after one frame is displayed. In a frame a single row of LEDs (8 LEDs) are diplayed.

keywords.txt

@@ -3,6 +3,7 @@
 ScrollingText8x8Display	KEYWORD1
 init	KEYWORD2
 displayText	KEYWORD2
+displayCharacter	KEYWORD2
 
 ScrollingDirection	KEYWORD3
 TOP_TO_BOTTOM	LITERAL1