File content as of revision 0:21ac4fe1ccf8:

/**
 * Seeeduino Arch + NFC Shield write a NDEF record to a NFC tag
 */


#include "mbed.h"
#include "PN532.h"

#if 0

#define LOG(args...)

#else
#include "USBSerial.h"

#define LOG(args...)        pc.printf(args)

USBSerial pc;
//Serial pc(USBTX, USBRX);
#endif

// PN532(mosi, miso, clk, cs)
PN532 nfc(P1_22, P1_21, P1_20, P0_2);

DigitalOut led1(LED1);

/*
    We can encode many different kinds of pointers to the card,
    from a URL, to an Email address, to a phone number, and many more
    check the library header .h file to see the large # of supported
    prefixes!
*/
// For a http://www. url:
const char *url = "seeedstudio.com";
uint8_t ndefprefix = NDEF_URIPREFIX_HTTP_WWWDOT;

// for an email address
//const char * url = "mail@example.com";
//uint8_t ndefprefix = NDEF_URIPREFIX_MAILTO;

// for a phone number
//const char * url = "+1 212 555 1212";
//uint8_t ndefprefix = NDEF_URIPREFIX_TEL;

int main()
{

    nfc.begin();
    uint32_t versiondata = nfc.getFirmwareVersion();
    if (! versiondata) {
        LOG("Didn't find PN532\r\n");
        while (1) {
            led1 = !led1;
            wait(0.1);
        }
    }

    LOG("Found chip PN5%2X\r\n", versiondata >> 24);
    LOG("Firmware V%d.%d\r\n", (versiondata >> 16) & 0xFF, (versiondata >> 8) & 0xFF);

    nfc.SAMConfig();


    while (1) {
        uint8_t success;                          // Flag to check if there was an error with the PN532
        uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 };  // Buffer to store the continueed UID
        uint8_t uidLength;                        // Length of the UID (4 or 7 bytes depending on ISO14443A card type)
        bool authenticated = false;               // Flag to indicate if the sector is authenticated

        // Use the default NDEF keys (these would have have set by mifareclassic_formatndef.pde!)
        uint8_t keya[6] = { 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5 };
        uint8_t keyb[6] = { 0xD3, 0xF7, 0xD3, 0xF7, 0xD3, 0xF7 };

        LOG("Place your NDEF formatted Mifare Classic card on the reader to update the NDEF record\r\n");

        // Wait for an ISO14443A type card (Mifare, etc.).  When one is found
        // 'uid' will be populated with the UID, and uidLength will indicate
        // if the uid is 4 bytes (Mifare Classic) or 7 bytes (Mifare Ultralight)
        success = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid, &uidLength, 0);

        if (success) {
            // Display some basic information about the card
            LOG("Found an ISO14443A card\r\n");
            LOG("UID length: %d\r\nUID Value: ", uidLength);
            for (uint8_t i = 0; i < uidLength; i++) {
                LOG("0x%X ", uid[i]);
            }

            // Make sure this is a Mifare Classic card
            if (uidLength != 4) {
                LOG("Ooops ... this doesn't seem to be a Mifare Classic card!\r\n");
                continue;
            }

            // We probably have a Mifare Classic card ...
            LOG("Seems to be a Mifare Classic card (4 byte UID)\r\n");

            // Check if this is an NDEF card (using first block of sector 1 from mifareclassic_formatndef.pde)
            // Must authenticate on the first key using 0xD3 0xF7 0xD3 0xF7 0xD3 0xF7
            success = nfc.mifareclassic_AuthenticateBlock (uid, uidLength, 4, 0, keyb);
            if (!success) {
                LOG("Unable to authenticate block 4 ... is this card NDEF formatted?\r\n");
                continue;
            }

            LOG("Authentication succeeded (seems to be an NDEF/NFC Forum tag) ...\r\n");

            // Authenticated seems to have worked
            // Try to write an NDEF record to sector 1
            // Use 0x01 for the URI Identifier Code to prepend "http://www."
            // to the url (and save some space).  For information on URI ID Codes
            // see http://www.ladyada.net/wiki/private/articlestaging/nfc/ndef
            if (strlen(url) > 38) {
                // The length is also checked in the WriteNDEFURI function, but lets
                // warn users here just in case they change the value and it's bigger
                // than it should be
                LOG("URI is too long ... must be less than 38 characters!\r\n");
                continue;
            }

            LOG("Updating sector 1 with URI as NDEF Message\r\n");

            // URI is within size limits ... write it to the card and report success/failure
            success = nfc.mifareclassic_WriteNDEFURI(1, ndefprefix, url);
            if (success) {
                LOG("NDEF URI Record written to sector 1\r\n");
                LOG("\r\n");
            } else {
                LOG("NDEF Record creation failed! :(\r\n");
            }
        } else {
            LOG("Didn't find a NFC tag\r\n");
        }

        // Wait a bit before trying again
        LOG("\n\nDone!\r\n");
        wait(1);
    }
}