Simple RFID tutorial

1#include <SPI.h>
2#include <MFRC522.h>
3 
4#define SS_PIN 10
5#define  RST_PIN 9
6MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance.
7  
8void setup() 
9{
10  pinMode(4,OUTPUT);
11  pinMode(3,OUTPUT);
12  Serial.begin(9600);   // Initiate a serial communication
13  SPI.begin();      // Initiate  SPI bus
14  mfrc522.PCD_Init();   // Initiate MFRC522
15  Serial.println("Approximate your  card to the reader...");
16  Serial.println();
17
18}
19void loop() 
20{
21  // Look for new cards
22  if ( ! mfrc522.PICC_IsNewCardPresent()) 
23  {
24    return;
25  }
26  // Select one of the cards
27  if ( ! mfrc522.PICC_ReadCardSerial())  
28  {
29    return;
30  }
31  //Show UID on serial monitor
32  Serial.print("UID  tag :");
33  String content= "";
34  byte letter;
35  for (byte i = 0; i <  mfrc522.uid.size; i++) 
36  {
37     Serial.print(mfrc522.uid.uidByte[i] < 0x10  ? " 0" : " ");
38     Serial.print(mfrc522.uid.uidByte[i], HEX);
39     content.concat(String(mfrc522.uid.uidByte[i]  < 0x10 ? " 0" : " "));
40     content.concat(String(mfrc522.uid.uidByte[i],  HEX));
41  }
42  Serial.println();
43  Serial.print("Message : ");
44  content.toUpperCase();
45  if (content.substring(1) == "53 F7 CE 18") //to find card uid go to the serial  moniter, scan your card and copy uid into the section
46
47  {
48    digitalWrite(4,HIGH);
49    digitalWrite(3,LOW);
50    Serial.println("Authorized access");
51    Serial.println();
52    delay(3000);
53  }
54 
55 else   {
56    digitalWrite(4,LOW);
57    digitalWrite(3,HIGH);
58    Serial.println(" Access denied");
59    delay(3000);
60  }
61}