title: How to get the UID of RFID in Arduino?
body: <p>I have a RFID-RC522 (MF-RC522) module and I'm using Arduino sketch program.
  To use this RFID, I downloaded the Arduino MFRC522 library.</p>
  
  <p>And I run the example code of library.</p>
  
  <p>Here is the code.</p>
  
  <pre><code>/*
   * MFRC522 - Library to use ARDUINO RFID MODULE KIT 13.56 MHZ WITH TAGS SPI W AND R BY COOQROBOT.
   * The library file MFRC522.h has a wealth of useful info. Please read it.
   * The functions are documented in MFRC522.cpp.
   *
   * Based on code Dr.Leong   ( WWW.B2CQSHOP.COM )
   * Created by Miguel Balboa (circuitito.com), Jan, 2012.
   * Rewritten by Søren Thing Andersen (access.thing.dk), fall of 2013 (Translation to English, refactored, comments, anti collision, cascade levels.)
   * Released into the public domain.
   *
   * Sample program showing how to read data from a PICC using a MFRC522 reader on the Arduino SPI interface.
   *----------------------------------------------------------------------------- empty_skull 
   * Aggiunti pin per arduino Mega
   * add pin configuration for arduino mega
   * http://mac86project.altervista.org/
   ----------------------------------------------------------------------------- Nicola Coppola
   * Pin layout should be as follows:
   * Signal     Pin              Pin               Pin
   *            Arduino Uno      Arduino Mega      MFRC522 board
   * ------------------------------------------------------------
   * Reset      9                5                 RST
   * SPI SS     10               53                SDA
   * SPI MOSI   11               51                MOSI
   * SPI MISO   12               50                MISO
   * SPI SCK    13               52                SCK
   *
   * The reader can be found on eBay for around 5 dollars. Search for "mf-rc522" on ebay.com. 
   */
  
  #include &lt;SPI.h&gt;
  #include &lt;MFRC522.h&gt;
  
  #define SS_PIN 10
  #define RST_PIN 9
  MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance.
  
  void setup() {
      Serial.begin(9600); // Initialize serial communications with the PC
      SPI.begin();            // Init SPI bus
      mfrc522.PCD_Init(); // Init MFRC522 card
      Serial.println("Scan PICC to see UID and type...");
  }
  
  void loop() {
      // Look for new cards
      if ( ! mfrc522.PICC_IsNewCardPresent()) {
          return;
      }
  
      // Select one of the cards
      if ( ! mfrc522.PICC_ReadCardSerial()) {
          return;
      }
  
      // Dump debug info about the card. PICC_HaltA() is automatically called.
      mfrc522.PICC_DumpToSerial(&amp;(mfrc522.uid));
  }
  </code></pre>
  
  <p>When I run this code and put one of the card to RFID reader, a lot of information show on Serial monitor of Arduino IDE. Something like this...
  (I couldn't post the images)</p>
  
  <pre><code>//
  Scan PICC to see UID and type...
  
  Card UID : 84 90 6C A7
  
  PICC type : MIFARE 1KB
  
  Sector Block 0 1 2 3 4 5 6 7 ...
  
  15     63   00 00 00 00 ...
  //
  </code></pre>
  
  <p>But What I need is just the Card UID. This case is 84 90 6C A7.</p>
  
  <p>Actually, I have project. I want to switch on LED if i put a certain Card of RFID. To do this, I need to read the Card UID and assign this to some variable on Arduino sketch program.</p>
  
  <p>But I don't know how to get the UID of RFID tag in this case(This library and functions are complicated for me). </p>
  
  <p>If anybody knows how to do this, please help me.</p>