谁能解释为什么我的 arduino c++ 代码不起作用

Question

我用 C++ 编码，以便它接受用户的输入，然后点亮相应的 LED 这是我的代码..

int rPin = 13;`
int gPin = 12;
int yPin = 11;
int dTime = 500;
String input;
//Strings
//String red = "red";
String prompt1 = "Enter the color : ";
String conformation = "Entered color is ";
void setup(){
  pinMode(rPin,OUTPUT);
  pinMode(gPin,OUTPUT);
  pinMode(yPin,OUTPUT);
  Serial.begin(9600);
}
void loop() {
  Serial.println(prompt1);
  input = Serial.readString();
  while(Serial.available() == 0) {
    
  }
  if (input == "red"){
    digitalWrite(rPin,HIGH);
    delay(dTime);
    digitalWrite(rPin,LOW);
    delay(dTime);
 } else if (input == "green"){
    digitalWrite(gPin,HIGH);
    delay(dTime);
    digitalWrite(gPin,LOW);
    delay(dTime);
 } else if (input == "yellow"){
    digitalWrite(yPin,HIGH);
    delay(dTime);
    digitalWrite(yPin,LOW);
    delay(dTime);
 } 
//  digitalWrite(gPin,HIGH);
//  digitalWrite(yPin,HIGH);

我的arduino电路连接没有问题，我检查了三次......