     return;
 
   // FIXME: Runs over after 50 days!
-  if (millis() - lastRead < 2000) {
+  if (millis() - lastRead < RFID_READ_NO_CARD) {
     lastRead = millis();
     return;
   }


bool checkRfidChecksum(const char* buffer) {
  uint16_t checkSum = 0;
  char checkSum_L = 0;
  char checkSum_H = 0;
  String hexstr = "";
  uint16_t tmp = 0;

  // Calculate
  for (int i = 0; i < (TAG_LENGTH - 2) / 2; i++) {

uint16_t fifoCount;     // count of all bytes currently in FIFO
uint8_t fifoBuffer[64];

// Lock related stuff
char rfidTag[TAG_LENGTH + 1];
char lockTag[TAG_LENGTH + 1];
bool locked = false;

// RFID read stuff
unsigned long lastRead = 0;
char buffer[TAG_LENGTH];
int count = 0;
#define RFID_READ_NO_CARD 1000

// Software serial for XBee module
SoftwareSerial xbeeSerial(2, 3); // RX, TX
