Trouble with RC-522 RFID reader comparing hex values

Other Hardware Sensors
1

Hi

I'm using the following code to successfully read IDs from MIFARE cards to the serial monitor.

#include <SPI.h>      
#include <MFRC522.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

int readflag;
byte readCard[4];           

#define SS_PIN 10
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN);  // Create MFRC522 instance.

///////////////////////////////////////// Setup ///////////////////////////////////
void setup() {
   
  Serial.begin(9600); 
  SPI.begin();         
  mfrc522.PCD_Init();   
  mfrc522.PCD_SetAntennaGain(mfrc522.RxGain_max); 

lcd.begin(20, 4);
  
    }

///////////////////////////////////////////////////////////////////////////////
  // Main loop
///////////////////////////////////////////////////////////////////////////////
void loop () {

 do {                                                               
   readflag = checkread(); 
  }
    while (!readflag); 

//If card detected do this

       recordid();
  }

///////////////////////////////////////////////////////////////////////////////
  // Stores the ID of the card that's been detected in readCard byte array
///////////////////////////////////////////////////////////////////////////////
void recordid() {
    mfrc522.PICC_IsNewCardPresent();
    mfrc522.PICC_ReadCardSerial();
   lcd.clear();
    for (int i = 0; i < 4; i++) { 
        readCard[i] = mfrc522.uid.uidByte[i];  
             Serial.print( mfrc522.uid.uidByte[i], HEX);  
              
        }
    Serial.println("");
    mfrc522.PICC_HaltA();
  }

     
/////////////////////////////////////////////
  // Returns 1 if a card has been detected
/////////////////////////////////////////////
int checkread() {
   if ( ! mfrc522.PICC_IsNewCardPresent()) { 
    return 0; }                                        //no card detected
   
    mfrc522.PICC_HaltA(); 
    return 1; }                                       //card detected

I have 12 cards and the serial monitor is telling me that their ID's are (hex):

3278CE3F
F5C9FD29
2FC640
82BA7A3F
2BD7A3F
52B77A3F
B2E5640
F2DD640
E2ECCC3F
22B3640
2FD640
73D5B7AC

I understand these are being stored in the readCard byte array.

I would like to compare the current value of this byte array to a known value to determine whether an instruction is run (e.g. a blink of an LED)

Something like this:

If (readCard = 2FD640) {
turn on LED
}

I have been able to do this successfully using this if statement:

if ( (uint32_t)readCard == 0x3FCE7832)

for example card one. However, it will not work with the cards with IDs that are not 8 digits long i.e. card 11 (2FD640).

Can anyone help me implement this in code?

Many thanks.