..
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:breadcrumbs: <a href="../../index.html">Home</a> / <a href="../../index.html#software-c">Software</a> / C/C++ - NFC/RFID Bricklet

.. |device_identifier_constant| replace:: There is also a :ref:`constant <nfc_rfid_bricklet_c_constants>` for the device identifier of this Bricklet.

.. _nfc_rfid_bricklet_c:

C/C++ - NFC/RFID Bricklet
=========================

This is the description of the :ref:`C/C++ API bindings <api_bindings_c>` for the :ref:`NFC/RFID Bricklet <nfc_rfid_bricklet>`. General information and technical
specifications for the NFC/RFID Bricklet are summarized in its :ref:`hardware description
<nfc_rfid_bricklet_description>`.

An :ref:`installation guide <api_bindings_c_install>` for the C/C++ API
bindings is part of their general description.

.. _nfc_rfid_bricklet_c_examples:


Examples
--------

The example code below is `Public Domain (CC0 1.0)
<http://creativecommons.org/publicdomain/zero/1.0/>`__.

Scan For Tags
^^^^^^^^^^^^^

`Download (example_scan_for_tags.c) <https://github.com/Tinkerforge/nfc-rfid-bricklet/raw/master/software/examples/c/example_scan_for_tags.c>`__

.. literalinclude:: NFCRFID_Bricklet_C_example_scan_for_tags.c
 :language: c
 :linenos:
 :tab-width: 4

Write Read Type2
^^^^^^^^^^^^^^^^

`Download (example_write_read_type2.c) <https://github.com/Tinkerforge/nfc-rfid-bricklet/raw/master/software/examples/c/example_write_read_type2.c>`__

.. literalinclude:: NFCRFID_Bricklet_C_example_write_read_type2.c
 :language: c
 :linenos:
 :tab-width: 4

.. _nfc_rfid_bricklet_c_api:

API
---

Every function of the C/C++ bindings returns an integer which describes an
error code. Data returned from the device, when a getter is called,
is handled via call by reference. These parameters are labeled with the
``ret_`` prefix.

Possible error codes are:

* E_OK = 0
* E_TIMEOUT = -1
* E_NO_STREAM_SOCKET = -2
* E_HOSTNAME_INVALID = -3
* E_NO_CONNECT = -4
* E_NO_THREAD = -5
* E_NOT_ADDED = -6 (unused since bindings version 2.0.0)
* E_ALREADY_CONNECTED = -7
* E_NOT_CONNECTED = -8
* E_INVALID_PARAMETER = -9
* E_NOT_SUPPORTED = -10
* E_UNKNOWN_ERROR_CODE = -11

as defined in :file:`ip_connection.h`.

All functions listed below are thread-safe.




Basic Functions
^^^^^^^^^^^^^^^


.. c:function:: void nfc_rfid_create(NFCRFID *nfc_rfid, const char *uid, IPConnection *ipcon)

 Creates the device object ``nfc_rfid`` with the unique device ID ``uid`` and adds
 it to the IPConnection ``ipcon``:

 .. code-block:: c

    NFCRFID nfc_rfid;
    nfc_rfid_create(&nfc_rfid, "YOUR_DEVICE_UID", &ipcon);

 This device object can be used after the IP connection has been connected
 (see examples :ref:`above <nfc_rfid_bricklet_c_examples>`).

.. c:function:: void nfc_rfid_destroy(NFCRFID *nfc_rfid)

 Removes the device object ``nfc_rfid`` from its IPConnection and destroys it.
 The device object cannot be used anymore afterwards.


.. c:function:: int nfc_rfid_request_tag_id(NFCRFID *nfc_rfid, uint8_t tag_type)

 To read or write a tag that is in proximity of the NFC/RFID Bricklet you 
 first have to call this function with the expected tag type as parameter.
 It is no problem if you don't know the tag type. You can cycle through 
 the available tag types until the tag gives an answer to the request.
 
 Current the following tag types are supported:
 
 * Mifare Classic (``tag_type`` = 0)
 * NFC Forum Type 1 (``tag_type`` = 1)
 * NFC Forum Type 2 (``tag_type`` = 2)
 
 After you call :c:func:`nfc_rfid_request_tag_id` the NFC/RFID Bricklet will try to read 
 the tag ID from the tag. After this process is done the state will change.
 You can either register the :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED` callback or you can poll
 :c:func:`nfc_rfid_get_state` to find out about the state change.
 
 If the state changes to *RequestTagIDError* it means that either there was 
 no tag present or that the tag is of an incompatible type. If the state 
 changes to *RequestTagIDReady* it means that a compatible tag was found 
 and that the tag ID could be read out. You can now get the tag ID by
 calling :c:func:`nfc_rfid_get_tag_id`.
 
 If two tags are in the proximity of the NFC/RFID Bricklet, this
 function will cycle through the tags. To select a specific tag you have
 to call :c:func:`nfc_rfid_request_tag_id` until the correct tag id is found.
 
 In case of any *Error* state the selection is lost and you have to
 start again by calling :c:func:`nfc_rfid_request_tag_id`.
 
 The following defines are available for this function:
 
 * NFC_RFID_TAG_TYPE_MIFARE_CLASSIC = 0
 * NFC_RFID_TAG_TYPE_TYPE1 = 1
 * NFC_RFID_TAG_TYPE_TYPE2 = 2
 
.. c:function:: int nfc_rfid_get_tag_id(NFCRFID *nfc_rfid, uint8_t *ret_tag_type, uint8_t *ret_tid_length, uint8_t ret_tid[7])

 Returns the tag type, tag ID and the length of the tag ID 
 (4 or 7 bytes are possible length). This function can only be called if the
 NFC/RFID is currently in one of the *Ready* states. The returned ID
 is the ID that was saved through the last call of :c:func:`nfc_rfid_request_tag_id`.
 
 To get the tag ID of a tag the approach is as follows:
 
 1. Call :c:func:`nfc_rfid_request_tag_id`
 2. Wait for state to change to *RequestTagIDReady* (see :c:func:`nfc_rfid_get_state` or
    :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED`)
 3. Call :c:func:`nfc_rfid_get_tag_id`
 
 The following defines are available for this function:
 
 * NFC_RFID_TAG_TYPE_MIFARE_CLASSIC = 0
 * NFC_RFID_TAG_TYPE_TYPE1 = 1
 * NFC_RFID_TAG_TYPE_TYPE2 = 2
 
.. c:function:: int nfc_rfid_get_state(NFCRFID *nfc_rfid, uint8_t *ret_state, bool *ret_idle)

 Returns the current state of the NFC/RFID Bricklet.
 
 On startup the Bricklet will be in the *Initialization* state. The
 initialization will only take about 20ms. After that it changes to *Idle*.
 
 The functions of this Bricklet can be called in the *Idle* state and all of
 the *Ready* and *Error* states.
 
 Example: If you call :c:func:`nfc_rfid_request_page`, the state will change to 
 *RequestPage* until the reading of the page is finished. Then it will change
 to either *RequestPageReady* if it worked or to *RequestPageError* if it
 didn't. If the request worked you can get the page by calling :c:func:`nfc_rfid_get_page`.
 
 The same approach is used analogously for the other API functions.
 
 Possible states are:
 
 * Initialization = 0
 * Idle = 128
 * Error = 192
 * RequestTagID = 2
 * RequestTagIDReady = 130
 * RequestTagIDError = 194
 * AuthenticatingMifareClassicPage = 3
 * AuthenticatingMifareClassicPageReady = 131
 * AuthenticatingMifareClassicPageError = 195
 * WritePage = 4
 * WritePageReady = 132
 * WritePageError = 196
 * RequestPage = 5
 * RequestPageReady = 133
 * RequestPageError = 197
 
 The following defines are available for this function:
 
 * NFC_RFID_STATE_INITIALIZATION = 0
 * NFC_RFID_STATE_IDLE = 128
 * NFC_RFID_STATE_ERROR = 192
 * NFC_RFID_STATE_REQUEST_TAG_ID = 2
 * NFC_RFID_STATE_REQUEST_TAG_ID_READY = 130
 * NFC_RFID_STATE_REQUEST_TAG_ID_ERROR = 194
 * NFC_RFID_STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE = 3
 * NFC_RFID_STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_READY = 131
 * NFC_RFID_STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_ERROR = 195
 * NFC_RFID_STATE_WRITE_PAGE = 4
 * NFC_RFID_STATE_WRITE_PAGE_READY = 132
 * NFC_RFID_STATE_WRITE_PAGE_ERROR = 196
 * NFC_RFID_STATE_REQUEST_PAGE = 5
 * NFC_RFID_STATE_REQUEST_PAGE_READY = 133
 * NFC_RFID_STATE_REQUEST_PAGE_ERROR = 197
 
.. c:function:: int nfc_rfid_authenticate_mifare_classic_page(NFCRFID *nfc_rfid, uint16_t page, uint8_t key_number, uint8_t key[6])

 Mifare Classic tags use authentication. If you want to read from or write to
 a Mifare Classic page you have to authenticate it beforehand.
 Each page can be authenticated with two keys: A (``key_number`` = 0) and B
 (``key_number`` = 1). A new Mifare Classic
 tag that has not yet been written to can can be accessed with key A
 and the default key ``[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]``.
 
 The approach to read or write a Mifare Classic page is as follows:
 
 1. Call :c:func:`nfc_rfid_request_tag_id`
 2. Wait for state to change to *RequestTagIDReady* (see :c:func:`nfc_rfid_get_state`
    or :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED`)
 3. If looking for a specific tag then call :c:func:`nfc_rfid_get_tag_id` and check if the
    expected tag was found, if it was not found got back to step 1
 4. Call :c:func:`nfc_rfid_authenticate_mifare_classic_page` with page and key for the page
 5. Wait for state to change to *AuthenticatingMifareClassicPageReady* (see
    :c:func:`nfc_rfid_get_state` or :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED`)
 6. Call :c:func:`nfc_rfid_request_page` or :c:func:`nfc_rfid_write_page` to read/write page
 
 The following defines are available for this function:
 
 * NFC_RFID_KEY_A = 0
 * NFC_RFID_KEY_B = 1
 
.. c:function:: int nfc_rfid_write_page(NFCRFID *nfc_rfid, uint16_t page, uint8_t data[16])

 Writes 16 bytes starting from the given page. How many pages are written
 depends on the tag type. The page sizes are as follows:
 
 * Mifare Classic page size: 16 byte (one page is written)
 * NFC Forum Type 1 page size: 8 byte (two pages are written)
 * NFC Forum Type 2 page size: 4 byte (four pages are written)
 
 The general approach for writing to a tag is as follows:
 
 1. Call :c:func:`nfc_rfid_request_tag_id`
 2. Wait for state to change to *RequestTagIDReady* (see :c:func:`nfc_rfid_get_state` or
    :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED`)
 3. If looking for a specific tag then call :c:func:`nfc_rfid_get_tag_id` and check if the
    expected tag was found, if it was not found got back to step 1
 4. Call :c:func:`nfc_rfid_write_page` with page number and data
 5. Wait for state to change to *WritePageReady* (see :c:func:`nfc_rfid_get_state` or
    :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED`)
 
 If you use a Mifare Classic tag you have to authenticate a page before you
 can write to it. See :c:func:`nfc_rfid_authenticate_mifare_classic_page`.
 
.. c:function:: int nfc_rfid_request_page(NFCRFID *nfc_rfid, uint16_t page)

 Reads 16 bytes starting from the given page and stores them into a buffer. 
 The buffer can then be read out with :c:func:`nfc_rfid_get_page`.
 How many pages are read depends on the tag type. The page sizes are 
 as follows:
 
 * Mifare Classic page size: 16 byte (one page is read)
 * NFC Forum Type 1 page size: 8 byte (two pages are read)
 * NFC Forum Type 2 page size: 4 byte (four pages are read)
 
 The general approach for reading a tag is as follows:
 
 1. Call :c:func:`nfc_rfid_request_tag_id`
 2. Wait for state to change to *RequestTagIDReady* (see :c:func:`nfc_rfid_get_state`
    or :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED`)
 3. If looking for a specific tag then call :c:func:`nfc_rfid_get_tag_id` and check if the
    expected tag was found, if it was not found got back to step 1
 4. Call :c:func:`nfc_rfid_request_page` with page number
 5. Wait for state to change to *RequestPageReady* (see :c:func:`nfc_rfid_get_state`
    or :c:data:`NFC_RFID_CALLBACK_STATE_CHANGED`)
 6. Call :c:func:`nfc_rfid_get_page` to retrieve the page from the buffer
 
 If you use a Mifare Classic tag you have to authenticate a page before you
 can read it. See :c:func:`nfc_rfid_authenticate_mifare_classic_page`.
 
.. c:function:: int nfc_rfid_get_page(NFCRFID *nfc_rfid, uint8_t ret_data[16])

 Returns 16 bytes of data from an internal buffer. To fill the buffer
 with specific pages you have to call :c:func:`nfc_rfid_request_page` beforehand.
 


Advanced Functions
^^^^^^^^^^^^^^^^^^

.. c:function:: int nfc_rfid_get_api_version(NFCRFID *nfc_rfid, uint8_t ret_api_version[3])

 Returns the version of the API definition (major, minor, revision) implemented
 by this API bindings. This is neither the release version of this API bindings
 nor does it tell you anything about the represented Brick or Bricklet.
 
.. c:function:: int nfc_rfid_get_response_expected(NFCRFID *nfc_rfid, uint8_t function_id, bool *ret_response_expected)

 Returns the response expected flag for the function specified by the function
 ID parameter. It is *true* if the function is expected to send a response,
 *false* otherwise.
 
 For getter functions this is enabled by default and cannot be disabled,
 because those functions will always send a response. For callback configuration
 functions it is enabled by default too, but can be disabled by
 :c:func:`nfc_rfid_set_response_expected`. For setter functions it is disabled by default
 and can be enabled.
 
 Enabling the response expected flag for a setter function allows to detect
 timeouts and other error conditions calls of this setter as well. The
 device will then send a response for this purpose. If this flag is disabled for
 a setter function then no response is send and errors are silently ignored,
 because they cannot be detected.
 
 See :c:func:`nfc_rfid_set_response_expected`
 for the list of function ID defines available for this function.
 
.. c:function:: int nfc_rfid_set_response_expected(NFCRFID *nfc_rfid, uint8_t function_id, bool response_expected)

 Changes the response expected flag of the function specified by the
 function ID parameter. This flag can only be changed for setter (default value:
 *false*) and callback configuration functions (default value: *true*). For
 getter functions it is always enabled and callbacks it is always disabled.
 
 Enabling the response expected flag for a setter function allows to detect
 timeouts and other error conditions calls of this setter as well. The
 device will then send a response for this purpose. If this flag is disabled for
 a setter function then no response is send and errors are silently ignored,
 because they cannot be detected.
 
 The following function ID defines are available for this function:
 
 * NFC_RFID_FUNCTION_REQUEST_TAG_ID = 1
 * NFC_RFID_FUNCTION_AUTHENTICATE_MIFARE_CLASSIC_PAGE = 4
 * NFC_RFID_FUNCTION_WRITE_PAGE = 5
 * NFC_RFID_FUNCTION_REQUEST_PAGE = 6
 
.. c:function:: int nfc_rfid_set_response_expected_all(NFCRFID *nfc_rfid, bool response_expected)

 Changes the response expected flag for all setter and callback configuration
 functions of this device at once.
 
.. c:function:: int nfc_rfid_get_identity(NFCRFID *nfc_rfid, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)

 Returns the UID, the UID where the Bricklet is connected to, 
 the position, the hardware and firmware version as well as the
 device identifier.
 
 The position can be 'a', 'b', 'c' or 'd'.
 
 The device identifier numbers can be found :ref:`here <device_identifier>`.
 |device_identifier_constant|
 


Callback Configuration Functions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


.. c:function:: void nfc_rfid_register_callback(NFCRFID *nfc_rfid, uint8_t id, void *callback, void *user_data)

 Registers a callback with ID ``id`` to the function ``callback``. The
 ``user_data`` will be given as a parameter of the callback.

 The available IDs with corresponding function signatures are listed
 :ref:`below <nfc_rfid_bricklet_c_callbacks>`.




.. _nfc_rfid_bricklet_c_callbacks:

Callbacks
^^^^^^^^^

Callbacks can be registered to receive
time critical or recurring data from the device. The registration is done
with the :c:func:`nfc_rfid_register_callback` function. The parameters consist of
the device object, the callback ID, the callback function and optional
user data:

 .. code-block:: c

    void my_callback(int p, void *user_data) {
        printf("parameter: %d\n", p);
    }

    nfc_rfid_register_callback(&nfc_rfid, NFC_RFID_CALLBACK_EXAMPLE, (void *)my_callback, NULL);

The available constants with corresponding callback function signatures
are described below.

.. note::
 Using callbacks for recurring events is *always* preferred
 compared to using getters. It will use less USB bandwidth and the latency
 will be a lot better, since there is no round trip time.

.. c:var:: NFC_RFID_CALLBACK_STATE_CHANGED

 .. code-block:: c

  void callback(uint8_t state, bool idle, void *user_data)


 This callback is called if the state of the NFC/RFID Bricklet changes.
 See :c:func:`nfc_rfid_get_state` for more information about the possible states.
 
 The following defines are available for this function:
 
 * NFC_RFID_STATE_INITIALIZATION = 0
 * NFC_RFID_STATE_IDLE = 128
 * NFC_RFID_STATE_ERROR = 192
 * NFC_RFID_STATE_REQUEST_TAG_ID = 2
 * NFC_RFID_STATE_REQUEST_TAG_ID_READY = 130
 * NFC_RFID_STATE_REQUEST_TAG_ID_ERROR = 194
 * NFC_RFID_STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE = 3
 * NFC_RFID_STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_READY = 131
 * NFC_RFID_STATE_AUTHENTICATING_MIFARE_CLASSIC_PAGE_ERROR = 195
 * NFC_RFID_STATE_WRITE_PAGE = 4
 * NFC_RFID_STATE_WRITE_PAGE_READY = 132
 * NFC_RFID_STATE_WRITE_PAGE_ERROR = 196
 * NFC_RFID_STATE_REQUEST_PAGE = 5
 * NFC_RFID_STATE_REQUEST_PAGE_READY = 133
 * NFC_RFID_STATE_REQUEST_PAGE_ERROR = 197
 


.. _nfc_rfid_bricklet_c_constants:

Constants
^^^^^^^^^

.. c:var:: NFC_RFID_DEVICE_IDENTIFIER

 This constant is used to identify a NFC/RFID Bricklet.

 The :c:func:`nfc_rfid_get_identity` function and the :c:data:`IPCON_CALLBACK_ENUMERATE`
 callback of the IP Connection have a ``device_identifier`` parameter to specify
 the Brick's or Bricklet's type.

