Measuring and Improving Serial Performance / Serial.flush() Blocks Forever on Nano 33 BLE Sense

Official Hardware Nano Family Nano 33 BLE Sense
8

have you tried this which would be more representative of bulk data transfer?

  unsigned long startClock = micros();
  for (int i = 1000; i > 0; i--) Serial.write(BYTE_TO_SEND);
  Serial.flush();
  unsigned long endClock = micros();

(and you have the cost of the for loop - so you might want to transfer 1000 bytes from an array (or random location) in memory) - may be it's more efficient at iterating

const byte BYTE_TO_SEND = 170; //b'10101010'.
const unsigned long NUMERATOR = 1000000000;

byte buffer[1000];

void setup() {
  Serial.begin(115200); //Does nothing on the nano 33 ble sense.
  while (!Serial); //Wait for serial port to connect. Needed for native USB on nano 33 ble sense.
  memset(buffer, sizeof buffer, BYTE_TO_SEND);

  unsigned long startClock = micros();
  Serial.write(buffer, sizeof buffer);
  Serial.flush();
  unsigned long endClock = micros();

  unsigned long bytesPerSecond = NUMERATOR / (endClock - startClock);
  Serial.println();
  Serial.print(bytesPerSecond);
  Serial.println(" bytes/second");
}

void loop() {}