File content as of revision 4:25a67f63d5a3:

#include <sstream>
#include "mbed.h"
#include "PN532.h"
#include "PN532_HSU.h"
#include "PN532_SPI.h"
#include "PN532_I2C.h"
#include "EthernetInterface.h"
#include "HTTPClient.h"

char* thingSpeakUrl = "http://api.thingspeak.com/update";
char* thingSpeakKey = "7QKJFB65MJBCNM3L";
EthernetInterface eth;
TCPSocketConnection sock;
DigitalOut red (LED1);   // error led
DigitalOut green (LED2);
DigitalOut buzz (D8);
Serial pc(USBTX, USBRX);

// ----------------------------------------- HSU
//HardwareSerial pn532_hsu (PC_10, PC_11);
//PN532_HSU pn532_if (pn532_hsu);

// ----------------------------------------- SPI
SPI pn532_spi (D11, D12, D13);
PN532_SPI pn532_if (pn532_spi, D10);

// ----------------------------------------- I2C
//I2C pn532_i2c (I2C_SDA, I2C_SCL);
//PN532_I2C pn532_if (pn532_i2c);

PN532 nfc(pn532_if);
void setup(void)
{
    red = 1;
    green = 1;
    uint32_t versiondata = 0;
    pc.baud(115200);
    while (1) {
        nfc.begin();
        versiondata = nfc.getFirmwareVersion();
        if (! versiondata) {
            pc.printf("Didn't find PN53x board\n\n\r");
            wait_ms(500);
        } else {
            break;
        }
    }
    pc.printf ("\rFound chip PN5%02X , Firmware ver. %d.%d\n",
               (versiondata>>24) & 0xFF,
               (versiondata>>16) & 0xFF,
               (versiondata>>8) & 0xFF);
    nfc.setPassiveActivationRetries(0xFF);

    // configure board to read RFID tags
    //nfc.SAMConfig();

    pc.printf ("\n\rWaiting for an ISO14443A card\n");
}


/*==============================================================================
 * \brief main entry
 */
int main()
{

    eth.init(); //Use DHCP
    eth.connect();
    printf("\n\rEthernet connected, and IP Address is %s\n\r", eth.getIPAddress());
    setup();

    while (1) {
        bool success;
        uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 };
        uint8_t uidLength;
        success = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, &uid[0], &uidLength);
        if (success) {
            pc.printf("\n\rFound a card!\n\r");
            pc.printf("UID Length: %d bytes\n\r", uidLength);
            pc.printf("UID Value: ");
            for (uint8_t i=0; i < uidLength; i++) {
                pc.printf(" 0x%02X", uid[i]);
            }
            uint8_t data[4];
            char card[4];
            memcpy(card, (const char[]) { 'a', 'n', 'i', 'k'
            }, sizeof card);
            // If you want to write something to block 4 to test with, uncomment
            // the following line and this text should be read back in a minute
            //memcpy(data, (const uint8_t[]) { 'a', 'n', 'i', 'k'
            //}, sizeof data);
            //success = nfc.mifareclassic_WriteDataBlock (4, data);

            // Try to read the contents of block 4
            success = nfc.mifareclassic_ReadDataBlock(4, data);
            if (success) {
                char s = 's';
                for (uint8_t i = 0; i < 4; i++) {
                    char c = data[i];
                    if(c!=card[i]) {
                        s='f';
                    }
                }
                char str[]="";
                int value = 0;
                if(s=='s') {
                    pc.printf("\n\rCard for Aniket Accessed\n\r");
                    strcat(str, "Aniket's Card Accessed");
                    value = 1;
                    green = 0;
                    buzz = 0;
                } else {
                    pc.printf("\n\rNo access for this card\n\r");
                    strcat(str,"Invalid Card Accessed");
                    value = 404;
                    red = 0;
                    buzz = 1;
                }
                HTTPClient http;
                char buffer[256];
                sprintf(buffer,"%s?api_key=%s&field1=%d",thingSpeakUrl,thingSpeakKey,value);
                printf("Send to %s\r\n", buffer);
                http.get(buffer, buffer , 10);
                wait_ms (5000);
                red = 1;
                green = 1;
            }

        } else {
            // PN532 probably timed out waiting for a card
            pc.printf("\n\rWaiting for a card\n\r");
            wait_ms (5000);
            buzz = 0;
        }
    }
    //    loop ();
    eth.disconnect();
}