Pass a second argument to print() or println() to set the number of decimal places in Arduino Serial library

float_places.ino

float aNumber = 999;

void setup() {
  Serial.begin(115200);
}

void loop() {
  /* TIL: 
   * the second argument in print is the number of decimal 
   * places printed when passed a float/double
   */ 
  Serial.println(aNumber, 6);

  aNumber = aNumber / 2.0f;
  if (aNumber < 0.0000005f) {
    Serial.println(F("fin."));
    pinMode(LED_BUILTIN, OUTPUT);
    while (1) {
      // indicate finished
      digitalWrite(LED_BUILTIN, HIGH);
      delay(500);
      digitalWrite(LED_BUILTIN, LOW);
      delay(500);
    }
  }
  delay(1000);
}