#include <SPI.h>

#include <MFRC522.h>

MFRC522 mfrc522(10, 9);

char code[8] = ""; // Inserire qui il codice esadecimale della RFID Card di riferimento; esempio: "8FA2EA29"

byte cdvl[4];

constexpr uint8_t Led_Rosso = 1;

constexpr uint8_t Led_Verde = 0;

void setup() {

    pinMode(Led_Rosso, OUTPUT);   

    pinMode(Led_Verde, OUTPUT);      

    VectorValue(code, cdvl);

    digitalWrite(Led_Rosso, LOW);        

    digitalWrite(Led_Verde, LOW);

    delay(1000);    

    digitalWrite(Led_Rosso, HIGH);        

    digitalWrite(Led_Verde, HIGH);     

}

void loop() { 

    SPI.begin();

    mfrc522.PCD_Init();

    if (mfrc522.PICC_IsNewCardPresent()){

      if (mfrc522.PICC_ReadCardSerial()) {

        if(CompareVector(mfrc522.uid.uidByte, cdvl, 0, 4)) {

          digitalWrite(Led_Verde, LOW);

          delay(1000);

          digitalWrite(Led_Verde, HIGH);          

        }

        else {      

          digitalWrite(Led_Rosso, LOW);

          delay(1000);

          digitalWrite(Led_Rosso, HIGH);

        }       

      }

    }

    mfrc522.PICC_HaltA();

    mfrc522.PCD_StopCrypto1();    

}

boolean CompareVector(byte *x, byte *z, byte inz, byte dv) {

    byte j;   

    boolean flg = true;

    for (j = inz; j      if(x[j] != z[j]) flg = false;           

    }

    return flg;

}

void VectorValue(char* code, byte *x) {

    byte j=0;

    for(byte i=0; i<8; i=i+2) {

      x[j] = HextoDec(code[i], code[i+1]);

      j=j+1;

    }

  }

byte HextoDec(char x, char y) {

    byte h, l, r;

    h = 0;

    l = 0;

    if(x>64) h = x - 55;

    else h = x - 48;

    if(y>64) l = y - 55;

    else l = y - 48;

    r = h*16 + l;

    return r;

  }