     return false;   
 }
 
+// calculates checksum by XOR-ing all bytes except STX and ETX
 unsigned char checksum(unsigned char A[], int numElements) {
   int i = 0;
   unsigned char BCC = A[0];

                          0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, BCC, ETX };
  unsigned char response[bufferSize];

  while(RDM880.available()) {
    response[i] = RDM880.read();
    Serial.print(response[i], HEX);

#define CMD_INCREMENT 0x24
#define CMD_GET_SNR 0x25

/* 
RFID Reader
  Uses RDM880 breakout board with RX connected to pin 2 and TX connected to pin 3. 
  Another serial interface is added by including the Software Serial library.
  Dummy signal from 3.3 V is connected to pin 4.

Input:
  RFID tags
  Signal from Pin 4

Output:
  Serial number of tag scanned
  Elapsed time

Operation:
  Reader waits until a tag is scanned, then prints the serial number of the tag.
  Reader now waits for "control" signal, and when that signal goes high, counts time.

Notes:
  Consult ISO14443 documentation on command/receive packet structures

*/

