Arduino LED graph bar sketch, which receives the signals from serial port.

Arduino LED graph bar sketch

const int baudRate = 9600;
const int ledCount = 10;
int ledPins[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
char msg = ' ';

void setup() {
  // loop over the pin array and set them all to output:
  for (int thisLed = 0; thisLed < ledCount; thisLed++) {
    pinMode(ledPins[thisLed], OUTPUT); 
  }
  Serial.begin(baudRate);
  Serial.print("Hi! This is Arduino\n");
}

void loop() {
  // loop over the LED array:
  while (Serial.available() > 0) {
    //ASCII to int conversion ex. 49(1) - 48(0) = 1
    msg = Serial.read() - '0';
    //Number between 0 = ASCII 48 and 9 ASCII 57
    if ( msg >= 0 && msg < 10 ) {
      int ledsLit = msg + 1;
      for (int thisLed = 0; thisLed < ledCount; thisLed++) {
        if (thisLed + 1 <= ledsLit) {
          digitalWrite(ledPins[thisLed], HIGH);
        } else {
          digitalWrite(ledPins[thisLed], LOW);
        }
      }
    }
  }
  
}