// FROM http://peppe8o.com

#include <Servo.h>

Servo myservo;  // create servo object to control a servo
char receivedPos;

void setup() {
  Serial.begin(9600);
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  myservo.write(90);  // on power on, move servo to central position
  Serial.println("Welcome!"); // banner on connection with instructions
  Serial.println("Use following keys to control SG90 Servo Motor");
  Serial.println("a: moves to absolute position 180 dregrees");
  Serial.println("s: moves to absolute position 90 dregrees");
  Serial.println("d: moves to absolute position 0 dregrees");
  Serial.println("other keys: no moves");
}

void loop() {
 while(Serial.available()) {
  String commands = Serial.readString(); // read the incoming data as string
  Serial.println("I read string: "+ commands); // feedback of data received
  receivedPos = commands.charAt(0); // convert to char to enable Switch Statement use
  switch (receivedPos) {
   case 'a': myservo.write(180); break;
   case 's': myservo.write(90); break;
   case 'd': myservo.write(0); break;
   default: break;
  }
 }

}