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

// Number of readers
#define NR_OF_READERS 5

// SS pins for each reader
const int ssPins[NR_OF_READERS] = {2, 3, 4, 5, 6};
const int rstPin = 9; // common RST pin

MFRC522 mfrc522[NR_OF_READERS];   // array of MFRC522 instances

void setup() {
  Serial.begin(9600);
  while (!Serial); // wait for Serial to initialize

  SPI.begin();      // initialize SPI bus

  for (uint8_t i = 0; i < NR_OF_READERS; i++) {
    mfrc522[i].PCD_Init(ssPins[i], rstPin); // Init each MFRC522 reader
    Serial.print(F("Reader "));
    Serial.print(i);
    Serial.println(F(" initialized."));
  }
}

void loop() {
  for (uint8_t i = 0; i < NR_OF_READERS; i++) {
    // Look for new cards
    if (mfrc522[i].PICC_IsNewCardPresent() && mfrc522[i].PICC_ReadCardSerial()) {
      Serial.print(F("Reader "));
      Serial.print(i);
      Serial.print(F(": UID: "));
      for (byte j = 0; j < mfrc522[i].uid.size; j++) {
        Serial.print(mfrc522[i].uid.uidByte[j] < 0x10 ? " 0" : " ");
        Serial.print(mfrc522[i].uid.uidByte[j], HEX);
      }
      Serial.println();
      //mfrc522[i].PICC_HaltA(); // Stop reading
    }
  }
}