Untitled

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <MFRC522.h>

#define RST_PIN 5 // Connect RST to digital pin 5

MFRC522 mfrc522; // Create MFRC522 instance

LiquidCrystal_I2C lcd(0x27,16,2); // set the LCD address to 0x27 for a 16 chars and 2 line display

void setup()
{
  Serial.begin(9600); // Initialize serial communications with the PC
  SPI.begin(); // Init SPI bus
  mfrc522.PCD_Init(); // Init MFRC522 card
  lcd.init(); // initialize the lcd 
  lcd.backlight();
  lcd.setCursor(3,0);
  lcd.print("Hello, world!");
}

void loop()
{
  // Look for new cards
  if ( ! mfrc522.PICC_IsNewCardPresent() || ! mfrc522.PICC_ReadCardSerial() ) {
    delay(50);
    return;
  }
  
  // Show UID on serial monitor
  Serial.print("UID tag :");
  String content= "";
  byte letter;
  for (byte i = 0; i < mfrc522.uid.size; i++) 
  {
     Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
     Serial.print(mfrc522.uid.uidByte[i], HEX);
     content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
     content.concat(String(mfrc522.uid.uidByte[i], HEX));
  }
  Serial.println();
  Serial.print("Message : ");
  content.toUpperCase();
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Card UID:");
  lcd.setCursor(0,1);
  lcd.print(content.substring(1));
  delay(1500);
}