Wheel control using serial

wheel_control.ino

#define LWheel 0
#define RWheel 1

// 0: not running, 1: only left is running, 2: only right is running, 3: both is running
int runningState = 0;

int priorRunningState = -1;

void setup() {
  Serial.begin(9600);
}

void loop() {
  if (Serial.available()) {
    String s = "";
    char c;
      
    while((c = Serial.read()) != -1) {
      s += c;
      delay(10);
    }

    if (s.startsWith("lr")) {
      runningState = 3;
      Serial.println("runningState: 3");
    } else if (s.startsWith("r")) {
      runningState = 2;
      Serial.println("runningState: 2");
    } else if (s.startsWith("l")) {
      runningState = 1;
      Serial.println("runningState: 1");
    } else if (s.startsWith("s")) {
      runningState = 0;
      Serial.println("runningState: 0");
    }
  }

  if (runningState == priorRunningState) {
    return;
  }
  
  switch(runningState) {
    case 0:
      analogWrite(LWheel, 0);
      analogWrite(RWheel, 0);
      priorRunningState = 0;
      break;
    case 1:
      analogWrite(LWheel, 255);
      analogWrite(RWheel, 0);
      priorRunningState = 1;
      break;
    case 2:
      analogWrite(LWheel, 0);
      analogWrite(RWheel, 255);
      priorRunningState = 2;
      break;
    case 3:
      analogWrite(LWheel, 255);
      analogWrite(RWheel, 255);
      priorRunningState = 3;
      break;
  }  
  delay(1000);
}