NDEF Records With Custom Title (mime type) ??? eg MEDIA: type/mymimetype not simply 'text/plain'

[veletron]

Hi

My application uses NFC for various reasons, and I need, at runtime to load up to 4 textural NDEF records onto the Nordic NRF 52832's NFC hardware.

If I wanted a simple text record or a URL record, this is, of course simple, but I use the tag content in an Intent Filter in Android to launch a specific app, and have that app perform a specific function based on the tag content. I am also supporting both iOS and Android pairing via NFC (obviously non-standard as iOS does not do standard NFC pairing). The android intent filter on NFC filters on the record title, not the record content - eg the blemacaddress in the screenshot below.

Please see the tag-scan (from Android NFC Tools app) which shows how I need the data to show up on the tag, and if you know how to achieve this, please shout - I can find no examples beyond text, url, pairing etc. When using the 'Media' type, what follows is the specific MIME-type, that, in my case is the 'ppa/blemacaddress'

My android intent filter in the MainActivity is thus:

[IntentFilter(
new [] {"android.nfc.action.NDEF_DISCOVERED"},
Categories=new[] {Intent.CategoryDefault},
DataMimeType = StaticDefs.Nfc.ProteusFixedIdentUuid,
DataPathPattern = StaticDefs.Nfc.ProteusFixedIdentUuidPayload)] //NB - dont appear to be able to filter on the payload apart from for standard NDEF record like URL.

PS: If this is a terrible way to achieve what I am trying to achieve then I guess I will just do it as a text record!

Nigel

[veletron]

Sorted this  by duplicating the nfc_text_rec.c/h files renamed to nfc_media_rec.c/h This essentially gives you a key/value pair for each NDEF record.

See below...

nfc_media_rec.c

#include "sdk_common.h"

#include <string.h>
#include "nfc_media_rec.h"
#include "nrf_error.h"

#define TEXT_REC_STATUS_SIZE          1     ///< Size of the status.
#define TEXT_REC_STATUS_UTF_POS       7     ///< Position of a character encoding type.
#define TEXT_REC_RESERVED_POS         6     ///< Reserved position.


/**
 * @brief Function for calculating payload size.
 */
__STATIC_INLINE uint32_t nfc_media_rec_payload_size_get(nfc_media_rec_payload_desc_t * p_nfc_rec_media_payload_desc)
{
    return (TEXT_REC_STATUS_SIZE
          + p_nfc_rec_media_payload_desc->lang_code_len
          + p_nfc_rec_media_payload_desc->data_len);
}

ret_code_t nfc_media_rec_payload_constructor(nfc_media_rec_payload_desc_t * p_nfc_rec_media_payload_desc,
                                            uint8_t                     * p_buff,
                                            uint32_t                    * p_len)
{
    if ((p_nfc_rec_media_payload_desc->lang_code_len == 0)
     || (p_nfc_rec_media_payload_desc->lang_code_len & (1 << TEXT_REC_RESERVED_POS))
     || (p_nfc_rec_media_payload_desc->lang_code_len & (1 << TEXT_REC_STATUS_UTF_POS))
     || (p_nfc_rec_media_payload_desc->p_lang_code   == NULL)
     || (p_nfc_rec_media_payload_desc->data_len      == 0)
     || (p_nfc_rec_media_payload_desc->p_data        == NULL)
     || (p_len                                      == NULL))
    {
        return NRF_ERROR_INVALID_PARAM;
    }

    uint32_t payload_size = (nfc_media_rec_payload_size_get(p_nfc_rec_media_payload_desc)-2);

    if (p_buff != NULL)
    {
        if (payload_size > *p_len)
        {
            return NRF_ERROR_NO_MEM;
        }

        memcpy(p_buff,
            p_nfc_rec_media_payload_desc->p_data,
            p_nfc_rec_media_payload_desc->data_len);
    }

    *p_len = payload_size;

    return NRF_SUCCESS;
}

nfc_media_rec.h

/**@file
 *
 * @defgroup nfc_text_rec Text records
 * @{
 * @ingroup  nfc_ndef_messages
 *
 * @brief    Generation of NFC NDEF MEDIA record descriptions.
 *
 */

#include "nfc_ndef_record.h"

/**
 * @brief Type of the Unicode Transformation Format.
 *
 * Values to specify the type of UTF for an NFC NDEF Text record.
 */
typedef enum
{
    UTF_8   = 0, ///< Unicode Transformation Format 8.
    UTF_16  = 1, ///< Unicode Transformation Format 16.
} nfc_media_rec_utf_type_t;

/**
 * @brief Text record payload descriptor.
 */
typedef struct
{
    nfc_media_rec_utf_type_t utf;    ///< Type of the Unicode Transformation Format.

    uint8_t const * p_lang_code;    ///< Pointer to the IANA language code.
    uint8_t         lang_code_len;  ///< Length of the IANA language code.

    uint8_t const * p_data;         ///< Pointer to the user text.
    uint32_t        data_len;       ///< Length of the user text.
} nfc_media_rec_payload_desc_t;

/**
 * @brief Constructor for an NFC NDEF Text record payload.
 *
 * @param[in]       p_nfc_rec_text_payload_desc Pointer to the Text record description.
 * @param[out]      p_buff                      Pointer to the payload destination. If NULL, function will
 *                                              calculate the expected size of the Text record payload.
 *
 * @param[in,out]   p_len                       Size of the available memory to write as input.
 *                                              Size of the generated record payload as output.
 */
ret_code_t nfc_media_rec_payload_constructor(nfc_media_rec_payload_desc_t * p_nfc_rec_media_payload_desc,
                                            uint8_t                     * p_buff,
                                            uint32_t                    * p_len);

/**
 *@brief Macro for creating and initializing an NFC NDEF record descriptor for a Text record.
 *
 * This macro creates and initializes an instance of type @ref nfc_ndef_record_desc_t and
 * an instance of type @ref nfc_text_rec_payload_desc_t, which together constitute
 * an instance of a Text record.
 *
 * Use the macro @ref NFC_NDEF_TEXT_RECORD_DESC to access the NDEF Text record descriptor instance.
 *
 * @param[in] NAME              Name of the created record descriptor instance.
 * @param[in] UTF               Unicode Transformation Format.
 * @param[in] P_LANG_CODE       Pointer to the IANA language code.
 * @param[in] LANG_CODE_LEN     Length of the IANA language code.
 * @param[in] P_MIME_DATA       Pointer to MIME data (eg the record title)
 * @param[in] MIME_DATA_LEN     The length of P_MIME_DATA
 * @param[in] P_PAYLOAD_DATA    Pointer to the data for the record payload
 * @param[in] PAYLOAD_DATA_LEN  The length of PAYLOAD_DATA_LEN
 */
#define NFC_NDEF_MEDIA_RECORD_DESC_DEF(NAME,                                 \
                                      UTF,                                  \
                                      P_LANG_CODE,                          \
                                      LANG_CODE_LEN,                        \
																			P_MIME_DATA,                            \
																			MIME_DATA_LEN,                          \
                                      P_PAYLOAD_DATA,                        \
                                      PAYLOAD_DATA_LEN)                      \
    nfc_media_rec_payload_desc_t NAME##_nfc_media_rec_payload_desc =        \
    {                                                                       \
        .utf            = UTF,                                              \
        .p_lang_code    = P_LANG_CODE,                                      \
        .lang_code_len  = LANG_CODE_LEN,                                    \
        .p_data         = P_PAYLOAD_DATA,                                           \
        .data_len       = PAYLOAD_DATA_LEN,                                         \
    };                                                                      \
    NFC_NDEF_GENERIC_RECORD_DESC_DEF(NAME,                                  \
                                     TNF_MEDIA_TYPE,                        \
                                     P_LANG_CODE,                           \
                                     LANG_CODE_LEN,                         \
                                     P_MIME_DATA,                          \
                                     MIME_DATA_LEN,                         \
                                     nfc_media_rec_payload_constructor,      \
                                     &(NAME##_nfc_media_rec_payload_desc))
		
/**
 * @brief Macro for accessing the NFC NDEF Text record descriptor
 * instance that was created with @ref NFC_NDEF_TEXT_RECORD_DESC_DEF.
 */
#define NFC_NDEF_MEDIA_RECORD_DESC(NAME) 	 NFC_NDEF_GENERIC_RECORD_DESC(NAME)

Called in the same way as for text records, thus:

static uint8_t ndef_msg_buf[256];

//List of NDEF MIME Identifiers 
const uint8_t PatientAppFixedId_Mime[] = {'p', 'p', 'a', '/', '8', '6', '2', '5', '8', '0', 'e', '2','-', 'd',   //Used to launch android intent
                                      	      '4', '6', 'f','-', '3', '0', '0', '8','-', '2', '3', '8', '0',     //Must be 1st record on tag
													                    '-', '5', '4', '8', 'c', '4', '1', 'c', '9', 'a', '2', '0', 'c'};  //Used to qualify tag as 'for proteus app'

//const  uint8_t TechAppFixedId_RecordId[] = {todo fill in GUID};
																							
const uint8_t ProteusTestConUuid_Mime[] = {'p', 'p', 'a', '/', 't', 'e', 's', 't', 'c', 'o', 'n', 'i', 'd'};                       //ppa/testconid
const uint8_t ProteusMacAddress_Mime[] =  {'p', 'p', 'a', '/', 'b', 'l', 'e', 'm', 'a', 'c', 'a', 'd', 'd', 'r', 'e', 's', 's'};   //ppa/blemacaddress
const uint8_t ProteusTagType_Mime[] 	=    {'p', 'p', 'a', '/', 't', 'a', 'g', 't', 'y', 'p', 'e'};                                //ppa/tagtype


//List of Record content strings
static const uint8_t PatientAppFixedUuid[] 	= {'7', '1', 'a', '1', '6', '8', '3', '9',  '-', '8', 'f', '4', '9', '-', '3', 'f', 'd', 'b',  
																				       '-',	'0', '4', '8', '5', '-', 'c', 'c', '2', 'a', 'f', '6', '1', '3', '6', 'e', 'c', '0'};
static const uint8_t Proteus_TagType_Text[] = {'B', 'l', 'e', 'C', 'o', 'n', 'n', 'e', 'c', 't'};

static const uint8_t ident_code[] = {NULL};							/**< en_code[] = language code. Left blank intentionally. */

void nfc_init()
{
	/* Set up NFC */
		uint32_t  err_code;
    err_code = nfc_t2t_setup(nfc_callback, NULL);
    APP_ERROR_CHECK(err_code);
}

ret_code_t ConfigureTagForNfcPairing(uint8_t *ProteusMacAddr)
{
    ret_code_t err_code;
	
	  //NFC_NDEF_TEXT_RECORD_DESC_DEF(PatientAppFixedId_NAME,UTF_8,ident_code,sizeof(Ident_code),PatientAppFixedId_RecordId,sizeof(PatientAppFixedId_RecordId));
																	
		//err_code = nfc_ndef_msg_record_add(&NFC_NDEF_MSG(nfc_text_msg),&NFC_NDEF_TEXT_RECORD_DESC(PatientAppFixedId_NAME));
	
		//uint8_t *payload = GetTextBytesFromHex(ProteusMacAddr,MAC_ADDR_LEN);
	
		//uint8_t size = sizeof(payload);
	
		//Add the Guid record - this is what the Android intent uses to launch the app
	  NFC_NDEF_MEDIA_RECORD_DESC_DEF(nfc_Proteus_GUID_rec,UTF_8,ident_code,sizeof(ident_code),PatientAppFixedId_Mime,sizeof(PatientAppFixedId_Mime),PatientAppFixedUuid,sizeof(PatientAppFixedUuid));
	
		//Add the MAC Address
		NFC_NDEF_MEDIA_RECORD_DESC_DEF(nfc_Proteus_MacAddress_rec,UTF_8,ident_code,sizeof(ident_code),ProteusMacAddress_Mime,sizeof(ProteusMacAddress_Mime),(uint8_t*)GetStringFromHex(ProteusMacAddr, MAC_ADDR_LEN),MAC_ADDR_LEN*2);
	
		//NFC_NDEF_MEDIA_RECORD_DESC_DEF(nfc_Proteus_GUID_rec,UTF_8,ident_code,sizeof(ident_code),(uint8_t*)GetStringFromHex(ProteusMacAddr, MAC_ADDR_LEN),MAC_ADDR_LEN*2);
				
		NFC_NDEF_MSG_DEF(nfc_text_msg, 4);
																
	  err_code = nfc_ndef_msg_record_add(&NFC_NDEF_MSG(nfc_text_msg),&NFC_NDEF_MEDIA_RECORD_DESC(nfc_Proteus_GUID_rec));			
		err_code = nfc_ndef_msg_record_add(&NFC_NDEF_MSG(nfc_text_msg),&NFC_NDEF_MEDIA_RECORD_DESC(nfc_Proteus_MacAddress_rec));			
																
		uint32_t  len = sizeof(ndef_msg_buf);
		err_code = nfc_ndef_msg_encode(&NFC_NDEF_MSG(nfc_text_msg),ndef_msg_buf,&len);
	
		VERIFY_SUCCESS(err_code);
	
		err_code = nfc_t2t_payload_set(ndef_msg_buf, len);
    APP_ERROR_CHECK(err_code);

    /* Start sensing NFC field */
    err_code = nfc_t2t_emulation_start();
    APP_ERROR_CHECK(err_code);
}