Fix initRandomSeed(). Minor code and doc changes

The call to generateRandomSeed() in initRandomSeed() was missing
parentheses.

Added keyword for generateRandomSeed.

Minor code changes, and documentation changes and additions.

keywords.txt

@@ -64,6 +64,7 @@ flashlight	KEYWORD2
 flipVertical	KEYWORD2
 flipHorizontal	KEYWORD2
 freeRGBled	KEYWORD2
+generateRandomSeed	KEYWORD2
 getBuffer	KEYWORD2
 getCursorX	KEYWORD2
 getCursorY	KEYWORD2

src/Arduboy2.cpp

@@ -277,22 +277,24 @@ int Arduboy2Base::cpuLoad()
 
 unsigned long Arduboy2Base::generateRandomSeed()
 {
+  unsigned long seed;
+
   power_adc_enable(); // ADC on
 
   // do an ADC read from an unconnected input pin
   ADCSRA |= _BV(ADSC); // start conversion (ADMUX has been pre-set in boot())
   while (bit_is_set(ADCSRA, ADSC)) { } // wait for conversion complete
 
-  unsigned long seed = (static_cast<unsigned long>(ADC) << 16) + micros();
+  seed = ((unsigned long)ADC << 16) + micros();
 
   power_adc_disable(); // ADC off
-  
+
   return seed;
 }
 
 void Arduboy2Base::initRandomSeed()
 {
-  randomSeed(generateRandomSeed);
+  randomSeed(generateRandomSeed());
 }
 
 /* Graphics */

src/Arduboy2.h

@@ -695,13 +695,17 @@ class Arduboy2Base : public Arduboy2Core
   /** \brief
    * Create a seed suitable for use with a random number generator.
    *
+   * \return A random value that can be used to seed a random number generator.
+   *
    * \details
-   * The seed is generated with a random value derived from entropy from an
+   * The returned value will be a random value derived from entropy from an
    * ADC reading of a floating pin combined with the microseconds since boot.
    *
    * This method is still most effective when called after a semi-random time,
    * such as after a user hits a button to start a game or other semi-random
    * event.
+   *
+   * \see initRandomSeed()
    */
   unsigned long generateRandomSeed();
 
@@ -711,11 +715,14 @@ class Arduboy2Base : public Arduboy2Core
    * \details
    * The Arduino random number generator is seeded with a random value
    * derived from entropy from an ADC reading of a floating pin combined with
-   * the microseconds since boot.
+   * the microseconds since boot. The seed value is provided by calling the
+   * `generateRandomSeed()` function.
    *
    * This method is still most effective when called after a semi-random time,
    * such as after a user hits a button to start a game or other semi-random
    * event.
+   *
+   * \see generateRandomSeed()
    */
   void initRandomSeed();