Adds pseudo random numbers generation (espressif#7848)

Author: SuGlider

cores/esp32/Arduino.h

@@ -137,9 +137,19 @@ typedef unsigned int word;
 void setup(void);
 void loop(void);
 
+// The default is using Real Hardware random number generator  
+// But when randomSeed() is called, it turns to Psedo random
+// generator, exactly as done in Arduino mainstream
+long random(long);
 long random(long, long);
-#endif
+// Calling randomSeed() will make random()
+// using pseudo random like in Arduino
 void randomSeed(unsigned long);
+// Allow the Application to decide if the random generator
+// will use Real Hardware random generation (true - default)
+// or Pseudo random generation (false) as in Arduino MainStream
+void useRealRandomGenerator(bool useRandomHW);
+#endif
 long map(long, long, long, long, long);
 
 #ifdef __cplusplus
@@ -207,8 +217,6 @@ void setToneChannel(uint8_t channel = 0);
 void tone(uint8_t _pin, unsigned int frequency, unsigned long duration = 0);
 void noTone(uint8_t _pin);
 
-// WMath prototypes
-long random(long);
 #endif /* __cplusplus */
 
 #include "pins_arduino.h"

cores/esp32/WMath.cpp

@@ -29,10 +29,22 @@ extern "C" {
 }
 #include "esp32-hal-log.h"
 
+// Allows the user to choose between Real Hardware
+// or Software Pseudo random generators for the
+// Arduino random() functions
+static bool s_useRandomHW = true;
+void useRealRandomGenerator(bool useRandomHW) {
+  s_useRandomHW = useRandomHW;
+}
+
+// Calling randomSeed() will force the
+// Pseudo Random generator like in 
+// Arduino mainstream API
 void randomSeed(unsigned long seed)
 {
     if(seed != 0) {
         srand(seed);
+        s_useRandomHW = false;
     }
 }
 
@@ -46,7 +58,9 @@ long random( long howbig )
   if (howbig < 0) {
     return (random(0, -howbig));
   }
-  return esp_random() % howbig;
+  // if randomSeed was called, fall back to software PRNG
+  uint32_t val = (s_useRandomHW) ? esp_random() : rand();
+  return val % howbig;
 }
 
 long random(long howsmall, long howbig)