code.ino

int G = 2;
int Y = 3;
int R = 4;
int DELAY_G = 3000;
int DELAY_Y = 1000;
int DELAY_R = 3000;

void setup()
{
  pinMode(G, OUTPUT);
  pinMode(Y, OUTPUT);
  pinMode(R, OUTPUT);
  Serial.begin(9600);
}

void loop()
{

  while (Serial.available() > 0) {
    char trigger = Serial.read();

    switch (trigger) {
      case 'R+':
        DELAY_R += 500;
        break;

      case 'R-':
        DELAY_R -= 500;
        break;


      case 'Y+':
        DELAY_Y += 500;
        break;

      case 'Y-':
        DELAY_Y -= 500;
        break;


      case 'G+':
        DELAY_G += 500;
        break;

      case 'G-':
        DELAY_G -= 500;
        break;

    }
  }
  green_light();
  delay(DELAY_G);
  yellow_light();
  delay(DELAY_Y);
  red_light();
  delay(DELAY_R);
  yellow_light_2();
  delay(DELAY_Y);
}


void green_light()
{
  digitalWrite(G, HIGH);
  digitalWrite(Y, LOW);
  digitalWrite(R, LOW);
}

void yellow_light()
{
  digitalWrite(G, LOW);
  digitalWrite(Y, HIGH);
  digitalWrite(R, LOW);
}

void red_light()
{
  digitalWrite(G, LOW);
  digitalWrite(Y, LOW);
  digitalWrite(R, HIGH);
}

void yellow_light_2()
{
  digitalWrite(G, LOW);
  digitalWrite(Y, HIGH);
  digitalWrite(R, HIGH);
}