message: Tympan: improve comments
diff: @@ -358,13 +358,13 @@ class TympanBase : public AudioControlAIC3206, public Print
  }
  static int FreeRam(void) {
  - #if defined(__IMXRT1062__)
  + #if defined(__IMXRT1062__) //this branch is for Teensy 4.1 (ie, Tympan RevE)
  //extern unsigned long _heap_start;
  extern unsigned long _heap_end;
  extern char *__brkval;
  return (char *)&_heap_end - __brkval;
  - #else
  + #else //this branch is for Teensy 3.6 (ie, Tympan RevC and RevD)
  char top; //this new variable is, in effect, the mem location of the edge of the heap
  return &top - reinterpret_cast<char*>(sbrk(0));
  #endif
  