#include <Servo.h>
Servo motor;
const int stopUs = 1500; // Adjust for your servo's actual neutral.
unsigned long startedAt = 0;
bool moving = false;

void setup() {
  Serial.begin(9600);
  motor.attach(9);
  motor.writeMicroseconds(stopUs);
  Serial.println("f: forward, r: reverse, s: stop; automatic stop after 2 seconds");
}

void loop() {
  while (Serial.available() > 0) {
    const char command = Serial.read();
    if (command == 'f' || command == 'r') {
      motor.writeMicroseconds(stopUs + (command == 'f' ? 100 : -100));
      startedAt = millis();
      moving = true;
    } else if (command == 's') {
      motor.writeMicroseconds(stopUs);
      moving = false;
    }
  }
  if (moving && millis() - startedAt >= 2000) {
    motor.writeMicroseconds(stopUs);
    moving = false;
  }
}