// https://forum.arduino.cc/t/sscanf-bug-what-i-am-doing-wrong/1046254

uint32_t myBeginTime;
uint32_t myEndTime;
uint32_t anotherBeginTime;
uint32_t anotherEndTime;
uint32_t bufferEmptyTime;

void setup()
{
  Serial.begin(9600);
  Serial.println("block no block");

//  for (int nn = 10; nn <= 100; nn += 10)
//    testBlockNoBlock(nn);

   testBlockNoBlock(30);
}

void testBlockNoBlock(int nChars)
{

Serial.print("test with ");
Serial.println(nChars);
Serial.println();

myBeginTime = micros();

   for (int i = 0; i < nChars; i ++)
   {
       Serial.write('X');     // send nChars X
   }
   Serial.println();

myEndTime = micros();

anotherBeginTime = micros();

   Serial.flush();

anotherEndTime = micros();

   int nAvailable = Serial.availableForWrite();

   Serial.print(nChars);
   Serial.print(" blocking time measurment : ");
   Serial.println(myEndTime - myBeginTime); 

   Serial.print(nChars);
   Serial.print(" flush() : ");
   Serial.println(anotherEndTime - anotherBeginTime); 

// - just reports 63. I guess the buffer is never really empty, haha.
//   Serial.print("          after serial flush,  availableForWrite() = ");
//   Serial.println(nAvailable);

   Serial.println();
   delay(777);  // why or why not, that is the question.

myBeginTime = micros();

   for (int i = 0; i < nChars; i ++)
   {
       Serial.write('X');     // send nChars X
   }
   Serial.println();

myEndTime = micros();

anotherBeginTime = micros();

  while (Serial.availableForWrite() != 63);  // just hanging out

anotherEndTime = micros();

   Serial.print(nChars);
   Serial.print(" non-blocking time measurment : ");
   Serial.println(myEndTime - myBeginTime); 

   Serial.print(nChars);
   Serial.print(" waiting for buffer to empty : ");
   Serial.println(anotherEndTime - anotherBeginTime); 
   Serial.println("");
}

void loop() { }