#include <SPI.h>
#include <MFRC522.h>
#define RST_PIN         9          // Configurable, see typical pin layout above
#define SS_1_PIN        10         // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 2
#define SS_2_PIN        8          // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 1
#define NR_OF_READERS   2
byte ssPins[] = {SS_1_PIN, SS_2_PIN};
MFRC522 mfrc522[NR_OF_READERS];   // Create MFRC522 instance.
/**
* Initialize.
*/
void setup() {
 Serial.begin(9600); // Initialize serial communications with the PC
 while (!Serial);    // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
 SPI.begin();        // Init SPI bus
 for (uint8_t reader = 0; reader < NR_OF_READERS; reader++) {
   mfrc522[reader].PCD_Init(ssPins[reader], RST_PIN); // Init each MFRC522 card
   Serial.print(F("Reader "));
   Serial.print(reader);
   Serial.print(F(": "));
   mfrc522[reader].PCD_DumpVersionToSerial();
 }
}
/**
* Main loop.
*/
void loop() {
 for (uint8_t reader = 0; reader < NR_OF_READERS; reader++) {
   // Look for new cards
   if (mfrc522[reader].PICC_IsNewCardPresent() && mfrc522[reader].PICC_ReadCardSerial()) {
     Serial.print(F("Reader "));
     Serial.print(reader);
     // Show some details of the PICC (that is: the tag/card)
     Serial.print(F(": Card UID:"));
     dump_byte_array(mfrc522[reader].uid.uidByte, mfrc522[reader].uid.size);
     Serial.println();
     Serial.print(F("PICC type: "));
     MFRC522::PICC_Type piccType = mfrc522[reader].PICC_GetType(mfrc522[reader].uid.sak);
     Serial.println(mfrc522[reader].PICC_GetTypeName(piccType));
     // Halt PICC
     mfrc522[reader].PICC_HaltA();
     // Stop encryption on PCD
     mfrc522[reader].PCD_StopCrypto1();
   } //if (mfrc522[reader].PICC_IsNewC
 } //for(uint8_t reader
}
/**
* Helper routine to dump a byte array as hex values to Serial.
*/
void dump_byte_array(byte *buffer, byte bufferSize) {
 for (byte i = 0; i < bufferSize; i++) {
   Serial.print(buffer[i] < 0x10 ? " 0" : " ");
   Serial.print(buffer[i], HEX);
 }
} 
****************************************************************************************************************

 /*
program by Shubham Shinganapure on 14-07-2019
for RFID Safe Locker 
*/
#include <SPI.h>
#include <MFRC522.h>
#define RST_PIN         9          // Configurable, see typical pin layout above
#define SS_1_PIN        10         // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 2
#define SS_2_PIN        8          // Configurable, take a unused pin, only HIGH/LOW required, must be diffrent to SS 1
#define NR_OF_READERS   2
byte ssPins[] = {SS_1_PIN, SS_2_PIN};
MFRC522 mfrc522[NR_OF_READERS];   // Create MFRC522 instance.
int ledRed = A1;
int rly = A3;
const int ledBlue =  A2;
int ledState = LOW;   
unsigned long previousMillis = 0;  
const long interval = 90; 
int flg=0;
void setup() {
 pinMode(ledRed,OUTPUT);
 pinMode(ledBlue,OUTPUT);
 pinMode(rly,OUTPUT);
 SPI.begin();        // Init SPI bus
 for (uint8_t reader = 0; reader < NR_OF_READERS; reader++) {
   mfrc522[reader].PCD_Init(ssPins[reader], RST_PIN); // Init each MFRC522 card
   //Serial.print(F("Reader "));
  // Serial.print(reader);
   //Serial.print(F(": "));
   mfrc522[reader].PCD_DumpVersionToSerial();
 }
}
/**
* Main loop.
*/
int i =0 ;
char arry2[5] = {0x06,0xF8,0x51,0x1B,0}; // put your cards ID here. for example my card ID is 06,F8,51,1B so write it by this way{0x06,0xF8,0x51,0x1B,0} 
 char arry[5] = {0};
void loop() {
  Blink();
  readTag();
             if(strncmp(arry2,arry,4) == 0)
                { 
                 digitalWrite(rly,HIGH);
                 digitalWrite(ledBlue,HIGH);
                 delay(5000);
                 digitalWrite(rly,LOW);
                 digitalWrite(ledBlue,LOW);
                 //arry[5] = {0};
                 memset(arry,0,5);
               flg=0;
                }
           if(flg==1 && (strncmp(arry2,arry,4) != 0)) 
           {
              digitalWrite(ledBlue,LOW);
              wrongID(); 
              memset(arry,0,5);
              flg=0;
               }
}
void wrongID()
{
 digitalWrite(ledRed,HIGH);
 delay(500);
 digitalWrite(ledRed,LOW);
 delay(500);
 digitalWrite(ledRed,HIGH);
 delay(500);
 digitalWrite(ledRed,LOW);
 delay(500);
 digitalWrite(ledRed,HIGH);
 delay(500);
 digitalWrite(ledRed,LOW);
  delay(500);
 digitalWrite(ledRed,HIGH);
 delay(500);
 digitalWrite(ledRed,LOW);
 delay(500);
 digitalWrite(ledRed,HIGH);
 delay(500);
 digitalWrite(ledRed,LOW);
 }
void readTag()
{
 for (uint8_t reader = 0; reader < NR_OF_READERS; reader++) {
   // Look for new cards
   if (mfrc522[reader].PICC_IsNewCardPresent() && mfrc522[reader].PICC_ReadCardSerial()) {
    // Serial.print(F("Reader "));
    // Serial.print(reader);
     // Show some details of the PICC (that is: the tag/card)
     //Serial.print(F(": Card UID:"));
     dump_byte_array(mfrc522[reader].uid.uidByte, mfrc522[reader].uid.size);
     //Serial.println();
     for(i = 0;i < 4;i++)
     {
      //Serial.print(mfrc522[reader].uid.uidByte[i],HEX);
      arry[i] =  mfrc522[reader].uid.uidByte[i];
     flg=1;
      //Serial.println(arry[i],HEX);
     } 
     for(i = 0;i < 4;i++)
            //Serial.print(arry[i],HEX);
             // Serial.println();
     //Serial.print(F("PICC type: "));
     MFRC522::PICC_Type piccType = mfrc522[reader].PICC_GetType(mfrc522[reader].uid.sak);
     //Serial.println(mfrc522[reader].PICC_GetTypeName(piccType));
     // Halt PICC
     mfrc522[reader].PICC_HaltA();
     // Stop encryption on PCD
     mfrc522[reader].PCD_StopCrypto1();
   } //if (mfrc522[reader].PICC_IsNewC
 } //for(uint8_t reader
} 
/**
* Helper routine to dump a byte array as hex values to Serial.
*/
void dump_byte_array(byte *buffer, byte bufferSize) {
 for (byte i = 0; i < bufferSize; i++) {
   //Serial.print(buffer[i] < 0x10 ? " 0" : " ");
   //Serial.print(buffer[i], HEX);
 }
}
void Blink() {
 unsigned long currentMillis = millis();
 if (currentMillis - previousMillis >= interval) {
   previousMillis = currentMillis;
   if (ledState == LOW) {
     ledState = HIGH;
   } else {
     ledState = LOW;
   }
   digitalWrite(ledBlue, ledState);
 }
}