File content as of revision 0:54bf4b21c7fa:

// readMifare code adapted from Adafruit-PN532 library.
// see: https://github.com/adafruit/Adafruit-PN532
//
// Original Author : Adafruit Industries
// Modified By     : Ben Zhang <benzh@eecs.berkeley.edu>
// Date            : 2014/09/17

/**************************************************************************/
/*! 
    This example will wait for any ISO14443A card or tag, and
    depending on the size of the UID will attempt to read from it.
   
    If the card has a 4-byte UID it is probably a Mifare
    Classic card, and the following steps are taken:
   
    - Authenticate block 4 (the first block of Sector 1) using
      the default KEYA of 0XFF 0XFF 0XFF 0XFF 0XFF 0XFF
    - If authentication succeeds, we can then read any of the
      4 blocks in that sector (though only block 4 is read here)
     
    If the card has a 7-byte UID it is probably a Mifare
    Ultralight card, and the 4 byte pages can be read directly.
    Page 4 is read by default since this is the first 'general-
    purpose' page on the tags.


This is an example sketch for the Adafruit PN532 NFC/RFID breakout boards
This library works with the Adafruit NFC breakout 
  ----> https://www.adafruit.com/products/364
 
Check out the links above for our tutorials and wiring diagrams 
These chips use SPI to communicate, 4 required to interface

Adafruit invests time and resources providing this open source code, 
please support Adafruit and open-source hardware by purchasing 
products from Adafruit!

*/
/**************************************************************************/

#include "mbed.h"
#include "Adafruit_PN532.h"

#define SS   PTD0
// PTD1 is also LED_BLUE
#define SCK  PTD1
#define MOSI PTD2
#define MISO PTD3

DigitalOut red(LED_RED);
DigitalOut green(LED_GREEN);

Serial pc(USBTX, USBRX);
Adafruit_PN532 nfc(SCK, MISO, MOSI, SS);

void loop(void);

int main() {
  pc.printf("Hello!\n");  
  // By default, red
  green = 1; red = 0;

  
  nfc.begin();

  uint32_t versiondata = nfc.getFirmwareVersion();
  if (! versiondata) {
    pc.printf("Didn't find PN53x board");
    while (1); // halt
  }
  // Got ok data, print it out!
  pc.printf("Found chip PN5%2X with Firmware ver. %d.%d\n",
            versiondata >> 24,
            (versiondata >> 16) & 0xFF,
            (versiondata >> 8) & 0xFF);
  
  // configure board to read RFID tags
  nfc.SAMConfig();
  
  pc.printf("Waiting for an ISO14443A Card ...\n");
  
  while(1) { loop(); }
}


void loop(void) {
  // Turn back to red  
  green = 1; red = 0;

  uint8_t success;
  uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 };  // Buffer to store the returned UID
  uint8_t uidLength;                        // Length of the UID (4 or 7 bytes depending on ISO14443A card type)
  
  // Wait for an ISO14443A type cards (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);
  
  if (success) {
    // Turn off to indicate Card swipe
    green = 1; red = 1;
    // Display some basic information about the card
    pc.printf("\n\nFound an ISO14443A card\n");
    pc.printf("  UID Length: %d bytes", uidLength);
    pc.printf("  UID Value: ");
    nfc.PrintHex(uid, uidLength);
    pc.printf("\n");
    
    if (uidLength == 4)
    {
      // We probably have a Mifare Classic card ... 
      pc.printf("Seems to be a Mifare Classic card (4 byte UID)\n");
      
      // Now we need to try to authenticate it for read/write access
      // Try with the factory default KeyA: 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
      pc.printf("Trying to authenticate block 4 with default KEYA value\n");
      uint8_t keya[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
      
      // Start with block 4 (the first block of sector 1) since sector 0
      // contains the manufacturer data and it's probably better just
      // to leave it alone unless you know what you're doing
      success = nfc.mifareclassic_AuthenticateBlock(uid, uidLength, 4, 0, keya);
      
      if (success)
      {
        // Turn green to indicate success
        green = 0; red = 1;
        pc.printf("Sector 1 (Blocks 4..7) has been authenticated\n");
        uint8_t data[16];
        
        // If you want to write something to block 4 to test with, remove
        // the definition of data above, and uncomment the following lines
        /************************************************************************
        uint8_t data[16] = { 'b', 'e', 'n', ' ', 'z', 'h', 'a', 'n', 'g' };
        success = nfc.mifareclassic_WriteDataBlock (4, data);
        if (success)
        {
          // Data seems to have been read ... spit it out
          pc.printf("Data Written to Block 4:\n\t");
          nfc.PrintHexChar(data, 16);
          pc.printf("\n");
          
          // Wait a bit before reading the card again
          wait(1);
        }
        else
        {
          pc.printf("Ooops ... unable to write the requested block.\n");
        }
        return;
        ************************************************************************/
        
        // Try to read the contents of block 4
        success = nfc.mifareclassic_ReadDataBlock(4, data);
        
        if (success)
        {
          // Data seems to have been read ... spit it out
          pc.printf("Reading Block 4:\n\t");
          nfc.PrintHexChar(data, 16);
          pc.printf("\n");
          
          // Wait a bit before reading the card again
          wait(1);
        }
        else
        {
          pc.printf("Ooops ... unable to read the requested block.  Try another key?\n");
        }
      }
      else
      {
        pc.printf("Ooops ... authentication failed: Try another key?\n");
      }
    }
    
    if (uidLength == 7)
    {
      // We probably have a Mifare Ultralight card ...
      pc.printf("Seems to be a Mifare Ultralight tag (7 byte UID)\n");
      
      // Try to read the first general-purpose user page (#4)
      pc.printf("Reading page 4\n");
      uint8_t data[32];
      success = nfc.mifareultralight_ReadPage (4, data);
      if (success)
      {
        // Data seems to have been read ... spit it out
        nfc.PrintHexChar(data, 4);
        pc.printf("\n");
        
        // Wait a bit before reading the card again
        wait(1);
      }
      else
      {
        pc.printf("Ooops ... unable to read the requested page!?\n");
      }
    }
  }
}