escstuff/testtool/testtool.ino

#include <Servo.h>

#define PIN_ESC 5

Servo esc;

void setup() {
  Serial.begin(115200);
  Serial.setTimeout(10);

  esc.attach(PIN_ESC);
}

void loop() {
  String s = Serial.readString();
  if (s == "")
    return;
  esc.writeMicroseconds(s.toInt());
  Serial.println(s.toInt());
}