MFRC522
=======

Arduino library for MFRC522 and other RFID RC522 based modules.

Read and write different types of Radio-Frequency IDentification (RFID) cards
on your Arduino using a RC522 based reader connected via the Serial Peripheral
Interface (SPI) interface.


.. _pin layout:

Pin Layout
----------

The following table shows the typical pin layout used:

+-----------+---------+-----------------------------+
|           | PCD     | Arduino                     |
|           +---------+---------+---------+---------+
|           | MFRC522 | Uno     | Mega    | Nano v3 |
+-----------+---------+---------+---------+---------+
| Signal    | Pin     | Pin     | Pin     | Pin     |
+===========+=========+=========+=========+=========+
| RST/Reset | RST     | 9 [1]_  | 5 [1]_  | D9      |
+-----------+---------+---------+---------+---------+
| SPI SS    | SDA     | 10 [2]_ | 53 [2]_ | D10     |
+-----------+---------+---------+---------+---------+
| SPI MOSI  | MOSI    | 11      | 52      | D11     |
+-----------+---------+---------+---------+---------+
| SPI MISO  | MISO    | 12      | 51      | D12     |
+-----------+---------+---------+---------+---------+
| SPI SCK   | SCK     | 13      | 50      | D13     |
+-----------+---------+---------+---------+---------+

.. [1] Configurable, typically defined as RST_PIN in Sketch.
.. [2] Configurable, typically defined as SS_PIN in Sketch.


Hardware
--------

There are three hardware components involved:

1. **Micro Controller**:

* An `Arduino`_ or compatible executing the Sketch using this library.

* Prices vary from USD 7 for clones, to USD 75 for "starter kits" (which
  might be a good choice if this is your first exposure to Arduino;
  check if such kit already includes the Arduino, Reader, and some Tags).

2. **Proximity Coupling Device (PCD)**:

* The PCD is the actual RFID **Reader** based on `NXP MFRC522`_ Contactless
  Reader Integrated Circuit).

* Readers can be found on `eBay`_ for around USD 5: search for *"rc522"*.

* You can also find them at several web stores, they are often included in
  *"starter kits"*; so check your favourite electronics provider as well.

3. **Proximity Integrated Circuit Card (PICC)**:

* The PICC is the RFID **Card** or **Tag** using the `ISO/IEC 14443A`_
  interface, for example Mifare or NTAG203.

* One or two might be included with the Reader or *"starter kit"* already.


Protocols
---------

1. The micro controller and the reader use SPI for communication.

* The protocol is described in the `NXP MFRC522`_ datasheet.

* See the `Pin Layout`_ section for details on connecting the pins.

2. The reader and the tags communicate using a 13.56 MHz electromagnetic field.

* The protocol is defined in ISO/IEC 14443-3:2011 Part 3.

  * Details are found in chapter 6 *"Type A – Initialization and anticollision"*.

  * See http://wg8.de/wg8n1496_17n3613_Ballot_FCD14443-3.pdf for a free version
    of the final draft (which might be outdated in some areas).


History
-------

The MFRC522 library was first created in Jan 2012 by Miguel Balboa (from
http://circuitito.com) based on code by Dr. Leong (from http://B2CQSHOP.com)
for *"Arduino RFID module Kit 13.56 Mhz with Tags SPI W and R By COOQRobot"*.

It was translated into English and rewritten/refactored in the fall of 2013
by Søren Thing Andersen (from http://access.thing.dk).


.. _arduino: http://arduino.cc/
.. _ebay: http://www.ebay.com/
.. _iso/iec 14443a: http://en.wikipedia.org/wiki/ISO/IEC_14443
.. _iso/iec 14443-3\:2011 part 3: 
.. _nxp mfrc522: http://www.nxp.com/documents/data_sheet/MFRC522.pdf