Code examples and extended information

/*  
 *  ------ [RFID1356_03] RFID Bus Example --------
 *
 *  Explanation: This sketch shows how Libelium's RFID/NFC 13.56 can be
 *  used for ticketing solutions, in this case we use the RFID/NFC to
 *  simulate a RFID access control inside a bus.
 *  First, we assignate a quantity of money to the card (with a secret
 *  password of course). After that, each trip will substract the fare.
 *  This can be also used for a gym or a parking, for example.
 *  
 *  Copyright (C) 2012 Libelium Comunicaciones Distribuidas S.L.
 *  http://www.libelium.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License
 *  along with this program. If not, see <http://www.gnu.org/licenses/>.
 *  
 *  Version:                0.1
 *  Design:                 David Gascon
 *  Implementation:         Ahmad Saad, Javier Solobera 
 */
​
​
#include <WaspRFID13.h>
​
// stores the status of the executed command:
uint8_t state;
// auxiliar buffer:
uint8_t aux[16];
// stores the UID (unique identifier) of a card:
uint8_t UID[4];
// stores the key or password:
uint8_t keyAccess[] = {
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
// EDIT: initial credit to put in the card (in cents!)
// it is also possible to put "credits"
int initialCredit = 800; // this is 8 euros (8*100 = 800)
//int initialCredit = 32000; // this is 320 euros (8*100 = 800)
​
// EDIT: the price per trip (in cents !)
// it is also possible to put 1 (if they are credits)
int tripFare = 105; // this is 1.05 euros (no problems with floats now)
​
boolean firstDone = false; // signal if the first credit write was done
int credit = 0; // stores the money inside the card
char text[16]; // for changing from one format to the other
boolean completed = false; // signals if all the process was successfuly completed
​
​
​
void setup()
{
  USB.ON();
  USB.println("RFID/NFC @ 13.56 MHz module started");
  // switchs ON the module, type B, and asigns the socket
  RFID13.ON(SOCKET0);
  delay(1000);
}
​
​
​
void loop()
{
  USB.print("\r\n++++++++++++++++++++++++++++++++++++");
  // **** init the RFID/NFC reader
  state = RFID13.init(UID, aux);
  if (aux[0] == aux[1])  // if so, there is no card on the EM field
  {
    USB.print("\r\nRequest error - no card found");
  }
  else // a card was found
  {
    // **** authenticate the key A of sector 1
    state = RFID13.authenticate(UID, 1, keyAccess);
    if (firstDone == false)  // this part is for adding credit
    {
      // **** if passed authentication in block 1, we are able to set the inital credit
      sprintf(text, "%d", initialCredit);
      RFID13.string2vector(text, aux);
      // **** write aux in block number 1, and check afterwards
      state = RFID13.writeAndCheck(aux, 1);
      if (state == 0)
      {
        for (int i=0; i<sizeof(text); i++) // clear this variable
        {
          text[i] = '\0';
        }
        firstDone = true;
        // **** check the 16 bytes in block 1
        state = RFID13.read(1, aux);
        if (state == 0)  // if the read command was successful, we show the data (16 bytes)
        {
          USB.print("\r\n  Initial credit set:  ");
          for (int i=0; i<16; i++)
          {
            if (aux[i] == '\0') // to avoid showing voids
              break;
            USB.print(aux[i], BYTE); // print the 16 bits of block number 1, now in ASCII code
          }
        }
      }
    } // end of "adding credit part"
    // **** if passed authentication in block 1, we will be able to read the data in this block (the credit)
    state = RFID13.read(1, aux);
    if (state == 0)  // if the read command was successful, we show the data (16 bytes)
    {
      USB.print("\r\n  Credit before the trip: ");
      for (int i=0; i<16; i++)
      {
        if (aux[i] == '\0') // to avoid showing voids
          break;
        USB.print(aux[i], BYTE); // print the 16 bytes of the block 1 (the first ones are the credit, the rest are NULLs)
      }
      credit = RFID13.vector2int(aux); // convert the card data to int
      if (credit >= tripFare)
      {
        sprintf(text, "%d", credit - tripFare);
        RFID13.string2vector(text, aux);
        for (int i=0; i<sizeof(text); i++)  // clear this variable
        {
          text[i] = '\0';
        }
        // **** write aux in block number 1, and check afterwards
        state = RFID13.write(1, aux);
        if (state == 0)
        {
          //miSerial.print(" -->  correct write checked");
          completed = true;
          credit = credit - tripFare; // only substract if success happened
          // **** check the 16 bytes in block 1
          state = RFID13.read(1, aux);
          if (state == 0)  // if the read command was successful, we show the data (16 bytes) 
          {
            USB.print("\r\n  Credit after the trip:  ");
            for (int i=0; i<16; i++)
            {
              if (aux[i] == '\0')  // to avoid showing voids
                break;
              USB.print(aux[i], BYTE); // print the 16 bits of block number 1, now in ASCII code
            }
          }
        }
      }
      else
      {
        USB.print("\r\n  ** Not enough credit");
      }
    }
  }
  if (completed == true)  // a complete operation was done !!!
  {
    USB.print("\r\n  ACCESS GRANTED !!");
    completed = false;
    for (int i=0; i<2; i++)  // blink the LED fast to show not-OK
    {
      Utils.blinkLEDs(50);
    }
  }
  else
  {
    for (int i=0; i<10; i++) // blink the LED fast to show not-OK
    {
      Utils.blinkLEDs(50);
    }
  }
  delay(2000); // wait some time in each loop
}