// BufferedOutput_at_115200.ino
#include "BufferedOutput.h"
createBufferedOutput(output, 66, DROP_UNTIL_EMPTY); // modes are DROP_UNTIL_EMPTY, DROP_IF_FULL or BLOCK_IF_FULL

const uint32_t BAUD_RATE = 115200;
unsigned long loopCounter = 0;
unsigned long startTime = 0;
void setup() {
  Serial.begin(BAUD_RATE);
  for (int i = 10; i > 0; i--) {
    Serial.print(' '); Serial.print(i);
    delay(500);
  }
  Serial.println();
  Serial.print("BAUD_RATE = "); Serial.println(BAUD_RATE);
  output.connect(Serial);  // <<<<< connect the buffered output to Serial 
}

void loop() {
  output.nextByteOut(); // <<<<<<<<<< need to call this each loop to release next byte from buffer
  if (loopCounter == 0) {
    startTime = millis();
  }
  loopCounter = loopCounter + 1; // or loopCounter++; i.e. add one each loop
  output.println(" a very looooooooooooog msg with looooooooooooots of data");  // <<< use output instead of Serial 
  output.print("Loop:"); output.print(loopCounter);
  output.print(" mS:");
  output.println(millis()- startTime);
  // rest of loop
  delay(1); // assume the rest of your sketch code takes 1mS to execute
}