#include "Arduino.h"

void setup()
{
  Serial.begin(0);
  delay(1000);
}

#define TXCHARS 10000

void loop()
{
  uint32_t i;
  uint8_t x = 85;
  uint32_t elapsed = micros();

  for (i = 0; i < TXCHARS; i++)
  {
    Serial.write(x);
  }

  elapsed = micros() - elapsed;
  Serial.println(" ");
  Serial.println("***");
  Serial.print("USB TX speed = ");
  Serial.print((1000.0 * TXCHARS) / elapsed, 2);
  Serial.println(" KBytes/sec");
  delay(1000);
}