RFID Password Manager

1#include <SPI.h>
2#include <MFRC522.h>
3#include <Keyboard.h>
4  
5#define SS_PIN 10
6#define RST_PIN 9
7 
8MFRC522 rfid(SS_PIN, RST_PIN);  // Instance of the class MFRC522
9 
10MFRC522::MIFARE_Key key; 
11
12// declares  two arrays (one for the known tags and one for the associated password (indexes  must match))
13// declares an int corresponding to the length of the two previous  arrays
14// declaring a string to store the UID of the last tag read by the sensor
15//  finally, declares a string that maps the DEC to HEX conversion
16
17String tags[]  = {"53 12 F4 11", "03 9F 2E 11", "tag3"}; // tags consist of four pairs of  hex digits with spaces between them (but NOT at the end)
18String pwds[] = {"AWhiteTagPassWord",  "ABlueTagPassWord", "pwd3"};
19int listSize = 3; //must at all times equal  the number of elements in the previous two arrays
20String readData;
21
22void  setup() { 
23  Serial.begin(9600);
24  SPI.begin(); // Init SPI bus
25  rfid.PCD_Init();  // Init RC522 
26  Keyboard.begin(); //Init keyboard
27}
28 
29void loop() {
30  
31  // Reset the loop if no new card present on the sensor/reader. This saves  the entire process when idle.
32  if ( ! rfid.PICC_IsNewCardPresent())
33    return;
34  
35  // Verify if the NUID has been read
36  if ( ! rfid.PICC_ReadCardSerial())
37    return;
38 
39  MFRC522::PICC_Type piccType = rfid.PICC_GetType(rfid.uid.sak);
40
41  //reads the tag's UID number: four pairs of HEX digits (pair of HEX digits = 4+4  bits or 1 byte), output by the mfrc lib in DEC
42  //converts each pair back to  HEX, prints the whole UID at the serial (so it can be learned to be inserted in  the read tags array) and attributes it to the readData string
43  for (int i =  0; i < rfid.uid.size; i++) {
44    String hexKey = "0123456789ABCDEF"; // key  for the DEC to HEX conversion
45    int working = int(rfid.uid.uidByte[i]); //  auxiliary variable for the DEC to HEX conversion
46    
47    Serial.print(hexKey[working/16]);//first  digit (16^1)
48    Serial.print(hexKey[working%16]);//second digit (16^0)
49
50    readData += hexKey[working/16];//first digit (16^1)
51    readData += hexKey[working%16];//second  digit (16^0)
52    
53    if (i < rfid.uid.size - 1) {//won't add a space after  the last byte 
54      Serial.print(" ");
55      readData += " "; 
56    }
57  }
58
59  Serial.println();
60
61  // checks if the read tag UID (readData)  is in the known tags array
62  // if so, tells the keyboard to print the value  with the same index in the passwords array
63  for (int i = 0; i < listSize; i++)  {
64    if (readData == tags[i]) {
65      Keyboard.print(pwds[i]);
66      break;
67    }
68  }
69
70  // empties the UID-storing string for the next reading
71  readData = "";
72 
73  rfid.PICC_HaltA(); // Halt PICC
74}