// Connections
// Arduino:          
//                                MFRC522
// Pin {{ RST_PIN }} ----------------------- RST
// Pin {{ SS_PIN }} ----------------------- SDA
// Pin * ----------------------- MOSI
// Pin * ----------------------- MISO
// Pin * ----------------------- SCK

/*

   Typical pin layout used:
   -----------------------------------------------------------------------------------------
               MFRC522      Arduino       Arduino   Arduino    Arduino          Arduino
               Reader/PCD   Uno/101       Mega      Nano v3    Leonardo/Micro   Pro Micro
   Signal      Pin          Pin           Pin       Pin        Pin              Pin
   -----------------------------------------------------------------------------------------
   RST/Reset   RST          9             5         D9         RESET/ICSP-5     RST
   SPI SS      SDA(SS)      10            53        D10        10               10
   SPI MOSI    MOSI         11 / ICSP-4   51        D11        ICSP-4           16
   SPI MISO    MISO         12 / ICSP-1   50        D12        ICSP-1           14
   SPI SCK     SCK          13 / ICSP-3   52        D13        ICSP-3           15

*/

#include <EEPROM.h>     // We are going to read and write PICC's UIDs from/to EEPROM
#include <SPI.h>        // RC522 Module uses SPI protocol
#include <MFRC522.h>  // Library for Mifare RC522 Devices

// Create MFRC522 instance.
#define SS_PIN {{ SS_PIN }}
#define RST_PIN {{ RST_PIN }}
MFRC522 mfrc522(SS_PIN, RST_PIN);

// Define MFRC5222 module key input.
MFRC522::MIFARE_Key key;

// Define the process controller and readCard byte.
int successUID;
byte readCard[4]; // Stores scanned ID read from RFID Module

// Define openUID and lastRead strings.
String openUID;
String lastRead;

void setup()
{
  //Protocol Configuration
  Serial.begin(9600);  // Initialize serial communications with PC
  SPI.begin();           // MFRC522 Hardware uses SPI protocol
  mfrc522.PCD_Init();    // Initialize MFRC522 Hardware

  // If you do not register a new UID to EEPROM yet, reload the code after turning these lines into uncommented.
  
  // Save the new card or key tag UID to EEPROM. But do not forget it only has 1KB memory.
  // Serial.print("Approximate the new card or key tag to scan and register new UID.");
  // do{
  // Wait for the new card reading process.
  // successUID = registerCardUID();
  // }while(!successUID);

  // Get the open UID from EEPROM.
  getUIDfromEEPROM();
  
  Serial.print("UID is received from EEPROM :\n----------------------------------\n");
  Serial.print(openUID);
}

void loop(){

UID();

}

int UID(){
  // Get the last UID from MFRC522.
  if ( ! mfrc522.PICC_IsNewCardPresent()){
    return;
  }
  if ( ! mfrc522.PICC_ReadCardSerial()){
    return;
  }
    for(int i=0;i<mfrc522.uid.size;i++){
    lastRead += mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ";
    lastRead += String(mfrc522.uid.uidByte[i], HEX);
    }
    // Arrange lastRead for comparing.
    lastRead.trim();
    lastRead.toUpperCase();

    Serial.println("New UID :\n----------------------------------\n");
    Serial.println(lastRead);

    // Check whether it is a new card or not.
    if(lastRead == openUID){
      Serial.println("STATUS: OK");
    }else{
      Serial.println("STATUS: NEW UID DETECTED!");   
    }

}

int registerCardUID() {
  // Detect the new card UID. 
  if ( ! mfrc522.PICC_IsNewCardPresent()) { 
    return 0;
  }
  if ( ! mfrc522.PICC_ReadCardSerial()) {
    return 0;
  }

  // Display the new UID.
  Serial.print("\n----------------------------------\nNew Card or Key Tag UID : ");
  for (int i = 0; i < mfrc522.uid.size; i++) {  //
    readCard[i] = mfrc522.uid.uidByte[i];
    Serial.print(readCard[i], HEX);
  }
  Serial.print("\n----------------------------------\n");
  
  // Save the new UID to EEPROM. 
  for ( int i = 0; i < mfrc522.uid.size; i++ ){
   EEPROM.write(i, readCard[i] );
  }
  Serial.print("UID is saved successfully to EEPROM.\nIf you want to save another card, use i+4(...) instead i.");
  
  // If the card reading process is successful, return 1 and end the reading process.
  mfrc522.PICC_HaltA();
  return 1;
}

int getUIDfromEEPROM(){
  // Get the open UID from EEPROM.
  for(int i=0;i<4;i++){
    openUID += EEPROM.read(i) < 0x10 ? " 0" : " ";
    openUID += String(EEPROM.read(i), HEX);
    }
  // Arrange openUID for comparing.
  openUID.trim();
  openUID.toUpperCase();
  }