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/**************************************************************************/
/*!
@file Adafruit_NFCShield_I2C.cpp
@author Adafruit Industries
@license BSD (see license.txt)
I2C Driver for NXP's PN532 NFC/13.56MHz RFID Transceiver

This is a library for the Adafruit PN532 NFC/RFID shields
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 I2C to communicate
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!

@section HISTORY

v1.4 - Added setPassiveActivationRetries()
v1.3 - Modified to work with I2C
v1.2 - Added writeGPIO()
- Added readGPIO()

v1.1 - Changed readPassiveTargetID() to handle multiple UID sizes
- Added the following helper functions for text display
static void PrintHex(const byte * data, const uint32_t numBytes)
static void PrintHexChar(const byte * pbtData, const uint32_t numBytes)
- Added the following Mifare Classic functions:
bool mifareclassic_IsFirstBlock (uint32_t uiBlock)
bool mifareclassic_IsTrailerBlock (uint32_t uiBlock)
uint8_t mifareclassic_AuthenticateBlock (uint8_t * uid, uint8_t uidLen, uint32_t blockNumber, uint8_t keyNumber, uint8_t * keyData)
uint8_t mifareclassic_ReadDataBlock (uint8_t blockNumber, uint8_t * data)
uint8_t mifareclassic_WriteDataBlock (uint8_t blockNumber, uint8_t * data)
- Added the following Mifare Ultalight functions:
uint8_t mifareultralight_ReadPage (uint8_t page, uint8_t * buffer)
*/
/**************************************************************************/
#if ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif

#include <Wire.h>
#ifdef __AVR__
#define WIRE Wire
#else // Arduino Due
#define WIRE Wire1
#endif

#include "Adafruit_NFCShield_I2C.h"

byte pn532ack[] = {0x00, 0x00, 0xFF, 0x00, 0xFF, 0x00};
byte pn532response_firmwarevers[] = {0x00, 0xFF, 0x06, 0xFA, 0xD5, 0x03};

// Uncomment these lines to enable debug output for PN532(I2C) and/or MIFARE related code
// #define PN532DEBUG
// #define MIFAREDEBUG

#define PN532_PACKBUFFSIZ 64
byte pn532_packetbuffer[PN532_PACKBUFFSIZ];

/**************************************************************************/
/*!
@brief Sends a single byte via I2C

@param x The byte to send
*/
/**************************************************************************/
static inline void wiresend(uint8_t x)
{
#if ARDUINO >= 100
    WIRE.write((uint8_t)x);
#else
    WIRE.send(x);
#endif
}

/**************************************************************************/
/*!
@brief Reads a single byte via I2C
*/
/**************************************************************************/
static inline uint8_t wirerecv(void)
{
#if ARDUINO >= 100
    return WIRE.read();
#else
    return WIRE.receive();
#endif
}

/**************************************************************************/
/*!
@brief Instantiates a new PN532 class

@param irq Location of the IRQ pin
@param reset Location of the RSTPD_N pin
*/
/**************************************************************************/
Adafruit_NFCShield_I2C::Adafruit_NFCShield_I2C(uint8_t irq, uint8_t reset) {
  _irq = irq;
  _reset = reset;

  pinMode(_irq, INPUT);
  pinMode(_reset, OUTPUT);
}

/**************************************************************************/
/*!
@brief Setups the HW
*/
/**************************************************************************/
void Adafruit_NFCShield_I2C::begin() {
  WIRE.begin();

  // Reset the PN532
  digitalWrite(_reset, HIGH);
  digitalWrite(_reset, LOW);
  delay(400);
  digitalWrite(_reset, HIGH);
}
 
/**************************************************************************/
/*!
@brief Prints a hexadecimal value in plain characters

@param data Pointer to the byte data
@param numBytes Data length in bytes
*/
/**************************************************************************/
void Adafruit_NFCShield_I2C::PrintHex(const byte * data, const uint32_t numBytes)
{
  uint32_t szPos;
  for (szPos=0; szPos < numBytes; szPos++)
  {
    Serial.print("0x");
    // Append leading 0 for small values
    if (data[szPos] <= 0xF)
      Serial.print("0");
    Serial.print(data[szPos]&0xff, HEX);
    if ((numBytes > 1) && (szPos != numBytes - 1))
    {
      Serial.print(" ");
    }
  }
  Serial.println("");
}

/**************************************************************************/
/*!
@brief Prints a hexadecimal value in plain characters, along with
the char equivalents in the following format

00 00 00 00 00 00 ......

@param data Pointer to the byte data
@param numBytes Data length in bytes
*/
/**************************************************************************/
void Adafruit_NFCShield_I2C::PrintHexChar(const byte * data, const uint32_t numBytes)
{
  uint32_t szPos;
  for (szPos=0; szPos < numBytes; szPos++)
  {
    // Append leading 0 for small values
    if (data[szPos] <= 0xF)
      Serial.print("0");
    Serial.print(data[szPos], HEX);
    if ((numBytes > 1) && (szPos != numBytes - 1))
    {
      Serial.print(" ");
    }
  }
  Serial.print(" ");
  for (szPos=0; szPos < numBytes; szPos++)
  {
    if (data[szPos] <= 0x1F)
      Serial.print(".");
    else
      Serial.print((char)data[szPos]);
  }
  Serial.println("");
}
 
/**************************************************************************/
/*!
@brief Checks the firmware version of the PN5xx chip

@returns The chip's firmware version and ID
*/
/**************************************************************************/
uint32_t Adafruit_NFCShield_I2C::getFirmwareVersion(void) {
  uint32_t response;

  pn532_packetbuffer[0] = PN532_COMMAND_GETFIRMWAREVERSION;

  if (! sendCommandCheckAck(pn532_packetbuffer, 1))
    return 0;

  // read data packet
  wirereaddata(pn532_packetbuffer, 12);
  
  // check some basic stuff
  if (0 != strncmp((char *)pn532_packetbuffer, (char *)pn532response_firmwarevers, 6)) {
#ifdef PN532DEBUG
    Serial.println("Firmware doesn't match!");
#endif
    return 0;
  }
  
  response = pn532_packetbuffer[7];
  response <<= 8;
  response |= pn532_packetbuffer[8];
  response <<= 8;
  response |= pn532_packetbuffer[9];
  response <<= 8;
  response |= pn532_packetbuffer[10];

  return response;
}


/**************************************************************************/
/*!
@brief Sends a command and waits a specified period for the ACK

@param cmd Pointer to the command buffer
@param cmdlen The size of the command in bytes
@param timeout timeout before giving up
@returns 1 if everything is OK, 0 if timeout occured before an
ACK was recieved
*/
/**************************************************************************/
// default timeout of one second
boolean Adafruit_NFCShield_I2C::sendCommandCheckAck(uint8_t *cmd, uint8_t cmdlen, uint16_t timeout) {
  uint16_t timer = 0;
  
  // write the command
  wiresendcommand(cmd, cmdlen);
  
  // Wait for chip to say its ready!
  while (wirereadstatus() != PN532_I2C_READY) {
    if (timeout != 0) {
      timer+=10;
      if (timer > timeout)
        return false;
    }
    delay(10);
  }
#ifdef PN532DEBUG
  Serial.println("IRQ received");
#endif
  
  // read acknowledgement
  if (!readackframe()) {
#ifdef PN532DEBUG
    Serial.println("No ACK frame received!");
#endif
    return false;
  }

  return true; // ack'd command
}

/**************************************************************************/
/*!
Writes an 8-bit value that sets the state of the PN532's GPIO pins
@warning This function is provided exclusively for board testing and
is dangerous since it will throw an error if any pin other
than the ones marked "Can be used as GPIO" are modified! All
pins that can not be used as GPIO should ALWAYS be left high
(value = 1) or the system will become unstable and a HW reset
will be required to recover the PN532.
pinState[0] = P30 Can be used as GPIO
pinState[1] = P31 Can be used as GPIO
pinState[2] = P32 *** RESERVED (Must be 1!) ***
pinState[3] = P33 Can be used as GPIO
pinState[4] = P34 *** RESERVED (Must be 1!) ***
pinState[5] = P35 Can be used as GPIO
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::writeGPIO(uint8_t pinstate) {
  uint8_t errorbit;

  // Make sure pinstate does not try to toggle P32 or P34
  pinstate |= (1 << PN532_GPIO_P32) | (1 << PN532_GPIO_P34);
  
  // Fill command buffer
  pn532_packetbuffer[0] = PN532_COMMAND_WRITEGPIO;
  pn532_packetbuffer[1] = PN532_GPIO_VALIDATIONBIT | pinstate; // P3 Pins
  pn532_packetbuffer[2] = 0x00; // P7 GPIO Pins (not used ... taken by I2C)

#ifdef PN532DEBUG
    Serial.print("Writing P3 GPIO: "); Serial.println(pn532_packetbuffer[1], HEX);
#endif

  // Send the WRITEGPIO command (0x0E)
  if (! sendCommandCheckAck(pn532_packetbuffer, 3))
    return 0x0;
  
  // Read response packet (00 00 FF PLEN PLENCHECKSUM D5 CMD+1(0x0F) DATACHECKSUM)
  wirereaddata(pn532_packetbuffer, 8);

#ifdef PN532DEBUG
    Serial.print("Received: ");
    PrintHex(pn532_packetbuffer, 8);
    Serial.println("");
#endif
  
  return (pn532_packetbuffer[6] == 0x0F);
}

/**************************************************************************/
/*!
Reads the state of the PN532's GPIO pins
@returns An 8-bit value containing the pin state where:
pinState[0] = P30
pinState[1] = P31
pinState[2] = P32
pinState[3] = P33
pinState[4] = P34
pinState[5] = P35
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::readGPIO(void) {
  pn532_packetbuffer[0] = PN532_COMMAND_READGPIO;

  // Send the READGPIO command (0x0C)
  if (! sendCommandCheckAck(pn532_packetbuffer, 1))
    return 0x0;
  
  // Read response packet (00 00 FF PLEN PLENCHECKSUM D5 CMD+1(0x0D) P3 P7 IO1 DATACHECKSUM)
  wirereaddata(pn532_packetbuffer, 11);

  /* READGPIO response should be in the following format:
byte Description
------------- ------------------------------------------
b0..6 Frame header and preamble
b7 P3 GPIO Pins
b8 P7 GPIO Pins (not used ... taken by I2C)
b9 Interface Mode Pins (not used ... bus select pins)
b10 checksum */
#ifdef PN532DEBUG
    Serial.print("Received: ");
    PrintHex(pn532_packetbuffer, 11);
    Serial.println("");
    Serial.print("P3 GPIO: 0x"); Serial.println(pn532_packetbuffer[7], HEX);
    Serial.print("P7 GPIO: 0x"); Serial.println(pn532_packetbuffer[8], HEX);
    Serial.print("IO GPIO: 0x"); Serial.println(pn532_packetbuffer[9], HEX);
    // Note: You can use the IO GPIO value to detect the serial bus being used
    switch(pn532_packetbuffer[9])
    {
      case 0x00: // Using UART
        Serial.println("Using UART (IO = 0x00)");
        break;
      case 0x01: // Using I2C
        Serial.println("Using I2C (IO = 0x01)");
        break;
      case 0x02: // Using I2C
        Serial.println("Using I2C (IO = 0x02)");
        break;
    }
#endif

  return pn532_packetbuffer[6];
}

/**************************************************************************/
/*!
@brief Configures the SAM (Secure Access Module)
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::SAMConfig(void) {
  pn532_packetbuffer[0] = PN532_COMMAND_SAMCONFIGURATION;
  pn532_packetbuffer[1] = 0x01; // normal mode;
  pn532_packetbuffer[2] = 0x14; // timeout 50ms * 20 = 1 second
  pn532_packetbuffer[3] = 0x01; // use IRQ pin!
  
  if (! sendCommandCheckAck(pn532_packetbuffer, 4))
     return false;

  // read data packet
  wirereaddata(pn532_packetbuffer, 8);
  
  return (pn532_packetbuffer[6] == 0x15);
}

/**************************************************************************/
/*!
Sets the MxRtyPassiveActivation byte of the RFConfiguration register
@param maxRetries 0xFF to wait forever, 0x00..0xFE to timeout
after mxRetries
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::setPassiveActivationRetries(uint8_t maxRetries) {
  pn532_packetbuffer[0] = PN532_COMMAND_RFCONFIGURATION;
  pn532_packetbuffer[1] = 5; // Config item 5 (MaxRetries)
  pn532_packetbuffer[2] = 0xFF; // MxRtyATR (default = 0xFF)
  pn532_packetbuffer[3] = 0x01; // MxRtyPSL (default = 0x01)
  pn532_packetbuffer[4] = maxRetries;

#ifdef MIFAREDEBUG
  Serial.print("Setting MxRtyPassiveActivation to "); Serial.print(maxRetries, DEC); Serial.println(" ");
#endif
  
  if (! sendCommandCheckAck(pn532_packetbuffer, 5))
    return 0x0; // no ACK
  
  return 1;
}

/***** ISO14443A Commands ******/

/**************************************************************************/
/*!
Waits for an ISO14443A target to enter the field
@param cardBaudRate Baud rate of the card
@param uid Pointer to the array that will be populated
with the card's UID (up to 7 bytes)
@param uidLength Pointer to the variable that will hold the
length of the card's UID.
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::readPassiveTargetID(uint8_t cardbaudrate, uint8_t * uid, uint8_t * uidLength) {
  pn532_packetbuffer[0] = PN532_COMMAND_INLISTPASSIVETARGET;
  pn532_packetbuffer[1] = 1; // max 1 cards at once (we can set this to 2 later)
  pn532_packetbuffer[2] = cardbaudrate;
  
  if (! sendCommandCheckAck(pn532_packetbuffer, 3))
  {
#ifdef PN532DEBUG
Serial.println("No card(s) read");
#endif
    return 0x0; // no cards read
  }
  
  // Wait for a card to enter the field
  uint8_t status = PN532_I2C_BUSY;
#ifdef PN532DEBUG
  Serial.println("Waiting for IRQ (indicates card presence)");
#endif
  while (wirereadstatus() != PN532_I2C_READY)
  {
delay(10);
  }

#ifdef PN532DEBUG
  Serial.println("Found a card");
  #endif
 
  // read data packet
  wirereaddata(pn532_packetbuffer, 20);
  
  // check some basic stuff
  /* ISO14443A card response should be in the following format:
byte Description
------------- ------------------------------------------
b0..6 Frame header and preamble
b7 Tags Found
b8 Tag Number (only one used in this example)
b9..10 SENS_RES
b11 SEL_RES
b12 NFCID Length
b13..NFCIDLen NFCID */
#ifdef MIFAREDEBUG
    Serial.print("Found "); Serial.print(pn532_packetbuffer[7], DEC); Serial.println(" tags");
#endif
  if (pn532_packetbuffer[7] != 1)
    return 0;
    
  uint16_t sens_res = pn532_packetbuffer[9];
  sens_res <<= 8;
  sens_res |= pn532_packetbuffer[10];
#ifdef MIFAREDEBUG
    Serial.print("ATQA: 0x"); Serial.println(sens_res, HEX);
    Serial.print("SAK: 0x"); Serial.println(pn532_packetbuffer[11], HEX);
#endif
  
  /* Card appears to be Mifare Classic */
  *uidLength = pn532_packetbuffer[12];
#ifdef MIFAREDEBUG
    Serial.print("UID:");
#endif
  for (uint8_t i=0; i < pn532_packetbuffer[12]; i++)
  {
    uid[i] = pn532_packetbuffer[13+i];
#ifdef MIFAREDEBUG
      Serial.print(" 0x");Serial.print(uid[i], HEX);
#endif
  }
#ifdef MIFAREDEBUG
    Serial.println();
#endif

  return 1;
}


/***** Mifare Classic Functions ******/

/**************************************************************************/
/*!
Indicates whether the specified block number is the first block
in the sector (block 0 relative to the current sector)
*/
/**************************************************************************/
bool Adafruit_NFCShield_I2C::mifareclassic_IsFirstBlock (uint32_t uiBlock)
{
  // Test if we are in the small or big sectors
  if (uiBlock < 128)
    return ((uiBlock) % 4 == 0);
  else
    return ((uiBlock) % 16 == 0);
}

/**************************************************************************/
/*!
Indicates whether the specified block number is the sector trailer
*/
/**************************************************************************/
bool Adafruit_NFCShield_I2C::mifareclassic_IsTrailerBlock (uint32_t uiBlock)
{
  // Test if we are in the small or big sectors
  if (uiBlock < 128)
    return ((uiBlock + 1) % 4 == 0);
  else
    return ((uiBlock + 1) % 16 == 0);
}

/**************************************************************************/
/*!
Tries to authenticate a block of memory on a MIFARE card using the
INDATAEXCHANGE command. See section 7.3.8 of the PN532 User Manual
for more information on sending MIFARE and other commands.

@param uid Pointer to a byte array containing the card UID
@param uidLen The length (in bytes) of the card's UID (Should
be 4 for MIFARE Classic)
@param blockNumber The block number to authenticate. (0..63 for
1KB cards, and 0..255 for 4KB cards).
@param keyNumber Which key type to use during authentication
(0 = MIFARE_CMD_AUTH_A, 1 = MIFARE_CMD_AUTH_B)
@param keyData Pointer to a byte array containing the 6 byte
key value
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::mifareclassic_AuthenticateBlock (uint8_t * uid, uint8_t uidLen, uint32_t blockNumber, uint8_t keyNumber, uint8_t * keyData)
{
  uint8_t len;
  uint8_t i;
  
  // Hang on to the key and uid data
  memcpy (_key, keyData, 6);
  memcpy (_uid, uid, uidLen);
  _uidLen = uidLen;

  #ifdef MIFAREDEBUG
  Serial.print("Trying to authenticate card ");
  Adafruit_NFCShield_I2C::PrintHex(_uid, _uidLen);
  Serial.print("Using authentication KEY ");Serial.print(keyNumber ? 'B' : 'A');Serial.print(": ");
  Adafruit_NFCShield_I2C::PrintHex(_key, 6);
#endif
  
  // Prepare the authentication command //
  pn532_packetbuffer[0] = PN532_COMMAND_INDATAEXCHANGE; /* Data Exchange Header */
  pn532_packetbuffer[1] = 1; /* Max card numbers */
  pn532_packetbuffer[2] = (keyNumber) ? MIFARE_CMD_AUTH_B : MIFARE_CMD_AUTH_A;
  pn532_packetbuffer[3] = blockNumber; /* Block Number (1K = 0..63, 4K = 0..255 */
  memcpy (pn532_packetbuffer+4, _key, 6);
  for (i = 0; i < _uidLen; i++)
  {
    pn532_packetbuffer[10+i] = _uid[i]; /* 4 byte card ID */
  }

  if (! sendCommandCheckAck(pn532_packetbuffer, 10+_uidLen))
    return 0;

  // Read the response packet
  wirereaddata(pn532_packetbuffer, 12);
  
  // Check if the response is valid and we are authenticated???
  // for an auth success it should be bytes 5-7: 0xD5 0x41 0x00
  // Mifare auth error is technically byte 7: 0x14 but anything other and 0x00 is not good
  if (pn532_packetbuffer[7] != 0x00)
  {
#ifdef PN532DEBUG
    Serial.print("Authentification failed: ");
    Adafruit_NFCShield_I2C::PrintHexChar(pn532_packetbuffer, 12);
#endif
    return 0;
  }
  
  return 1;
}

/**************************************************************************/
/*!
Tries to read an entire 16-byte data block at the specified block
address.

@param blockNumber The block number to authenticate. (0..63 for
1KB cards, and 0..255 for 4KB cards).
@param data Pointer to the byte array that will hold the
retrieved data (if any)
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::mifareclassic_ReadDataBlock (uint8_t blockNumber, uint8_t * data)
{
#ifdef MIFAREDEBUG
  Serial.print("Trying to read 16 bytes from block ");Serial.println(blockNumber);
#endif
  
  /* Prepare the command */
  pn532_packetbuffer[0] = PN532_COMMAND_INDATAEXCHANGE;
  pn532_packetbuffer[1] = 1; /* Card number */
  pn532_packetbuffer[2] = MIFARE_CMD_READ; /* Mifare Read command = 0x30 */
  pn532_packetbuffer[3] = blockNumber; /* Block Number (0..63 for 1K, 0..255 for 4K) */

  /* Send the command */
  if (! sendCommandCheckAck(pn532_packetbuffer, 4))
  {
#ifdef MIFAREDEBUG
    Serial.println("Failed to receive ACK for read command");
#endif
    return 0;
  }

  /* Read the response packet */
  wirereaddata(pn532_packetbuffer, 26);

  /* If byte 8 isn't 0x00 we probably have an error */
  if (pn532_packetbuffer[7] != 0x00)
  {
#ifdef MIFAREDEBUG
    Serial.println("Unexpected response");
    Adafruit_NFCShield_I2C::PrintHexChar(pn532_packetbuffer, 26);
#endif
    return 0;
  }
    
  /* Copy the 16 data bytes to the output buffer */
  /* Block content starts at byte 9 of a valid response */
  memcpy (data, pn532_packetbuffer+8, 16);

  /* Display data for debug if requested */
#ifdef MIFAREDEBUG
    Serial.print("Block ");
    Serial.println(blockNumber);
    Adafruit_NFCShield_I2C::PrintHexChar(data, 16);
#endif

  return 1;
}

/**************************************************************************/
/*!
Tries to write an entire 16-byte data block at the specified block
address.

@param blockNumber The block number to authenticate. (0..63 for
1KB cards, and 0..255 for 4KB cards).
@param data The byte array that contains the data to write.
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::mifareclassic_WriteDataBlock (uint8_t blockNumber, uint8_t * data)
{
#ifdef MIFAREDEBUG
  Serial.print("Trying to write 16 bytes to block ");Serial.println(blockNumber);
#endif
  
  /* Prepare the first command */
  pn532_packetbuffer[0] = PN532_COMMAND_INDATAEXCHANGE;
  pn532_packetbuffer[1] = 1; /* Card number */
  pn532_packetbuffer[2] = MIFARE_CMD_WRITE; /* Mifare Write command = 0xA0 */
  pn532_packetbuffer[3] = blockNumber; /* Block Number (0..63 for 1K, 0..255 for 4K) */
  memcpy (pn532_packetbuffer+4, data, 16); /* Data Payload */

  /* Send the command */
  if (! sendCommandCheckAck(pn532_packetbuffer, 20))
  {
#ifdef MIFAREDEBUG
    Serial.println("Failed to receive ACK for write command");
#endif
    return 0;
  }
  delay(10);
  
  /* Read the response packet */
  wirereaddata(pn532_packetbuffer, 26);

  return 1;
}

/**************************************************************************/
/*!
Formats a Mifare Classic card to store NDEF Records
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::mifareclassic_FormatNDEF (void)
{
  uint8_t sectorbuffer1[16] = {0x14, 0x01, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1};
  uint8_t sectorbuffer2[16] = {0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1, 0x03, 0xE1};
  uint8_t sectorbuffer3[16] = {0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0x78, 0x77, 0x88, 0xC1, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

  // Note 0xA0 0xA1 0xA2 0xA3 0xA4 0xA5 must be used for key A
  // for the MAD sector in NDEF records (sector 0)
  
  // Write block 1 and 2 to the card
  if (!(mifareclassic_WriteDataBlock (1, sectorbuffer1)))
    return 0;
  if (!(mifareclassic_WriteDataBlock (2, sectorbuffer2)))
    return 0;
  // Write key A and access rights card
  if (!(mifareclassic_WriteDataBlock (3, sectorbuffer3)))
    return 0;

  // Seems that everything was OK (?!)
  return 1;
}

/**************************************************************************/
/*!
Writes an NDEF URI Record to the specified sector (1..15)
Note that this function assumes that the Mifare Classic card is
already formatted to work as an "NFC Forum Tag" and uses a MAD1
file system. You can use the NXP TagWriter app on Android to
properly format cards for this.

@param sectorNumber The sector that the URI record should be written
to (can be 1..15 for a 1K card)
@param uriIdentifier The uri identifier code (0 = none, 0x01 =
"http://www.", etc.)
@param url The uri text to write (max 38 characters).
@returns 1 if everything executed properly, 0 for an error
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::mifareclassic_WriteNDEFURI (uint8_t sectorNumber, uint8_t uriIdentifier, const char * url)
{
  // Figure out how long the string is
  uint8_t len = strlen(url);
  
  // Make sure we're within a 1K limit for the sector number
  if ((sectorNumber < 1) || (sectorNumber > 15))
    return 0;
  
  // Make sure the URI payload is between 1 and 38 chars
  if ((len < 1) || (len > 38))
    return 0;
    
  // Note 0xD3 0xF7 0xD3 0xF7 0xD3 0xF7 must be used for key A
  // in NDEF records

  // Setup the sector buffer (w/pre-formatted TLV wrapper and NDEF message)
  uint8_t sectorbuffer1[16] = {0x00, 0x00, 0x03, len+5, 0xD1, 0x01, len+1, 0x55, uriIdentifier, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
  uint8_t sectorbuffer2[16] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
  uint8_t sectorbuffer3[16] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
  uint8_t sectorbuffer4[16] = {0xD3, 0xF7, 0xD3, 0xF7, 0xD3, 0xF7, 0x7F, 0x07, 0x88, 0x40, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
  if (len <= 6)
  {
    // Unlikely we'll get a url this short, but why not ...
    memcpy (sectorbuffer1+9, url, len);
    sectorbuffer1[len+9] = 0xFE;
  }
  else if (len == 7)
  {
    // 0xFE needs to be wrapped around to next block
    memcpy (sectorbuffer1+9, url, len);
    sectorbuffer2[0] = 0xFE;
  }
  else if ((len > 7) || (len <= 22))
  {
    // Url fits in two blocks
    memcpy (sectorbuffer1+9, url, 7);
    memcpy (sectorbuffer2, url+7, len-7);
    sectorbuffer2[len-7] = 0xFE;
  }
  else if (len == 23)
  {
    // 0xFE needs to be wrapped around to final block
    memcpy (sectorbuffer1+9, url, 7);
    memcpy (sectorbuffer2, url+7, len-7);
    sectorbuffer3[0] = 0xFE;
  }
  else
  {
    // Url fits in three blocks
    memcpy (sectorbuffer1+9, url, 7);
    memcpy (sectorbuffer2, url+7, 16);
    memcpy (sectorbuffer3, url+23, len-24);
    sectorbuffer3[len-22] = 0xFE;
  }
  
  // Now write all three blocks back to the card
  if (!(mifareclassic_WriteDataBlock (sectorNumber*4, sectorbuffer1)))
    return 0;
  if (!(mifareclassic_WriteDataBlock ((sectorNumber*4)+1, sectorbuffer2)))
    return 0;
  if (!(mifareclassic_WriteDataBlock ((sectorNumber*4)+2, sectorbuffer3)))
    return 0;
  if (!(mifareclassic_WriteDataBlock ((sectorNumber*4)+3, sectorbuffer4)))
    return 0;

  // Seems that everything was OK (?!)
  return 1;
}

/***** Mifare Ultralight Functions ******/

/**************************************************************************/
/*!
Tries to read an entire 4-byte page at the specified address.

@param page The page number (0..63 in most cases)
@param buffer Pointer to the byte array that will hold the
retrieved data (if any)
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::mifareultralight_ReadPage (uint8_t page, uint8_t * buffer)
{
  if (page >= 64)
  {
#ifdef MIFAREDEBUG
    Serial.println("Page value out of range");
#endif
    return 0;
  }

#ifdef MIFAREDEBUG
    Serial.print("Reading page ");Serial.println(page);
#endif

  /* Prepare the command */
  pn532_packetbuffer[0] = PN532_COMMAND_INDATAEXCHANGE;
  pn532_packetbuffer[1] = 1; /* Card number */
  pn532_packetbuffer[2] = MIFARE_CMD_READ; /* Mifare Read command = 0x30 */
  pn532_packetbuffer[3] = page; /* Page Number (0..63 in most cases) */

  /* Send the command */
  if (! sendCommandCheckAck(pn532_packetbuffer, 4))
  {
#ifdef MIFAREDEBUG
    Serial.println("Failed to receive ACK for write command");
#endif
    return 0;
  }
  
  /* Read the response packet */
  wirereaddata(pn532_packetbuffer, 26);
#ifdef MIFAREDEBUG
    Serial.println("Received: ");
    Adafruit_NFCShield_I2C::PrintHexChar(pn532_packetbuffer, 26);
#endif

  /* If byte 8 isn't 0x00 we probably have an error */
  if (pn532_packetbuffer[7] == 0x00)
  {
    /* Copy the 4 data bytes to the output buffer */
    /* Block content starts at byte 9 of a valid response */
    /* Note that the command actually reads 16 byte or 4 */
    /* pages at a time ... we simply discard the last 12 */
    /* bytes */
    memcpy (buffer, pn532_packetbuffer+8, 4);
  }
  else
  {
#ifdef MIFAREDEBUG
      Serial.println("Unexpected response reading block: ");
      Adafruit_NFCShield_I2C::PrintHexChar(pn532_packetbuffer, 26);
#endif
    return 0;
  }

  /* Display data for debug if requested */
#ifdef MIFAREDEBUG
    Serial.print("Page ");Serial.print(page);Serial.println(":");
    Adafruit_NFCShield_I2C::PrintHexChar(buffer, 4);
#endif

  // Return OK signal
  return 1;
}



/************** high level I2C */


/**************************************************************************/
/*!
@brief Tries to read the PN532 ACK frame (not to be confused with
the I2C ACK signal)
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::readackframe(void) {
  uint8_t ackbuff[6];
  
  wirereaddata(ackbuff, 6);
    
  return (0 == strncmp((char *)ackbuff, (char *)pn532ack, 6));
}

/************** mid level I2C */

/**************************************************************************/
/*!
@brief Checks the IRQ pin to know if the PN532 is ready
@returns 0 if the PN532 is busy, 1 if it is free
*/
/**************************************************************************/
uint8_t Adafruit_NFCShield_I2C::wirereadstatus(void) {
  uint8_t x = digitalRead(_irq);
  
  if (x == 1)
    return PN532_I2C_BUSY;
  else
    return PN532_I2C_READY;
}

/**************************************************************************/
/*!
@brief Reads n bytes of data from the PN532 via I2C

@param buff Pointer to the buffer where data will be written
@param n Number of bytes to be read
*/
/**************************************************************************/
void Adafruit_NFCShield_I2C::wirereaddata(uint8_t* buff, uint8_t n) {
  uint16_t timer = 0;
  
  delay(2);

#ifdef PN532DEBUG
  Serial.print("Reading: ");
#endif
  // Start read (n+1 to take into account leading 0x01 with I2C)
  WIRE.requestFrom((uint8_t)PN532_I2C_ADDRESS, (uint8_t)(n+2));
  // Discard the leading 0x01
  wirerecv();
  for (uint8_t i=0; i<n; i++) {
    delay(1);
    buff[i] = wirerecv();
#ifdef PN532DEBUG
    Serial.print(" 0x");
    Serial.print(buff[i], HEX);
#endif
  }
  // Discard trailing 0x00 0x00
  // wirerecv();
#ifdef PN532DEBUG
  Serial.println();
#endif
}

/**************************************************************************/
/*!
@brief Writes a command to the PN532, automatically inserting the
preamble and required frame details (checksum, len, etc.)

@param cmd Pointer to the command buffer
@param cmdlen Command length in bytes
*/
/**************************************************************************/
void Adafruit_NFCShield_I2C::wiresendcommand(uint8_t* cmd, uint8_t cmdlen) {
  uint8_t checksum;

  cmdlen++;
#ifdef PN532DEBUG
  Serial.print("\nSending: ");
#endif

  delay(2); // or whatever the delay is for waking up the board

  // I2C START
  WIRE.beginTransmission(PN532_I2C_ADDRESS);
  checksum = PN532_PREAMBLE + PN532_PREAMBLE + PN532_STARTCODE2;
  wiresend(PN532_PREAMBLE);
  wiresend(PN532_PREAMBLE);
  wiresend(PN532_STARTCODE2);

  wiresend(cmdlen);
  wiresend(~cmdlen + 1);
 
  wiresend(PN532_HOSTTOPN532);
  checksum += PN532_HOSTTOPN532;

#ifdef PN532DEBUG
  Serial.print(" 0x"); Serial.print(PN532_PREAMBLE, HEX);
  Serial.print(" 0x"); Serial.print(PN532_PREAMBLE, HEX);
  Serial.print(" 0x"); Serial.print(PN532_STARTCODE2, HEX);
  Serial.print(" 0x"); Serial.print(cmdlen, HEX);
  Serial.print(" 0x"); Serial.print(~cmdlen + 1, HEX);
  Serial.print(" 0x"); Serial.print(PN532_HOSTTOPN532, HEX);
#endif

  for (uint8_t i=0; i<cmdlen-1; i++) {
   wiresend(cmd[i]);
   checksum += cmd[i];
#ifdef PN532DEBUG
   Serial.print(" 0x"); Serial.print(cmd[i], HEX);
#endif
  }
  
  wiresend(~checksum);
  wiresend(PN532_POSTAMBLE);
  
  // I2C STOP
  WIRE.endTransmission();

#ifdef PN532DEBUG
  Serial.print(" 0x"); Serial.print(~checksum, HEX);
  Serial.print(" 0x"); Serial.print(PN532_POSTAMBLE, HEX);
  Serial.println();
#endif
}

/**************************************************************************/
/*!
@brief Waits until the PN532 is ready.

@param timeout Timeout before giving up
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::waitUntilReady(uint16_t timeout) {
  uint16_t timer = 0;
  while(wirereadstatus() != PN532_I2C_READY) {
    if (timeout != 0) {
      timer += 10;
      if (timer > timeout) {
        return false;
      }
    }
    delay(10);
  }
  return true;
}

/**************************************************************************/
/*!
@brief Exchanges an APDU with the currently inlisted peer

@param send Pointer to data to send
@param sendLength Length of the data to send
@param response Pointer to response data
@param responseLength Pointer to the response data length
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::inDataExchange(uint8_t * send, uint8_t sendLength, uint8_t * response, uint8_t * responseLength) {
  if (sendLength > PN532_PACKBUFFSIZ -2) {
#ifdef PN532DEBUG
      Serial.println("APDU length too long for packet buffer");
#endif
    return false;
  }
  uint8_t i;
  
  pn532_packetbuffer[0] = 0x40; // PN532_COMMAND_INDATAEXCHANGE;
  pn532_packetbuffer[1] = inListedTag;
  for (i=0; i<sendLength; ++i) {
    pn532_packetbuffer[i+2] = send[i];
  }
  
  if (!sendCommandCheckAck(pn532_packetbuffer,sendLength+2,1000)) {
#ifdef PN532DEBUG
      Serial.println("Could not send ADPU");
#endif
    return false;
  }

  if (!waitUntilReady(1000)) {
#ifdef PN532DEBUG
      Serial.println("Response never received for ADPU...");
#endif
    return false;
  }

  wirereaddata(pn532_packetbuffer,sizeof(pn532_packetbuffer));
  
  if (pn532_packetbuffer[0] == 0 && pn532_packetbuffer[1] == 0 && pn532_packetbuffer[2] == 0xff) {
    uint8_t length = pn532_packetbuffer[3];
    if (pn532_packetbuffer[4]!=(uint8_t)(~length+1)) {
#ifdef PN532DEBUG
        Serial.println("Length check invalid");
        Serial.println(length,HEX);
        Serial.println((~length)+1,HEX);
#endif
      return false;
    }
    if (pn532_packetbuffer[5]==PN532_PN532TOHOST && pn532_packetbuffer[6]==PN532_RESPONSE_INDATAEXCHANGE) {
      if ((pn532_packetbuffer[7] & 0x3f)!=0) {
#ifdef PN532DEBUG
          Serial.println("Status code indicates an error");
#endif
        return false;
      }
      
      length -= 3;
      
      if (length > *responseLength) {
        length = *responseLength; // silent truncation...
      }
      
      for (i=0; i<length; ++i) {
        response[i] = pn532_packetbuffer[8+i];
      }
      *responseLength = length;
      
      return true;
    }
    else {
      Serial.print("Don't know how to handle this command: ");
      Serial.println(pn532_packetbuffer[6],HEX);
      return false;
    }
  }
  else {
    Serial.println("Preamble missing");
    return false;
  }
}

/**************************************************************************/
/*!
@brief 'InLists' a passive target. PN532 acting as reader/initiator,
peer acting as card/responder.
*/
/**************************************************************************/
boolean Adafruit_NFCShield_I2C::inListPassiveTarget() {
  pn532_packetbuffer[0] = PN532_COMMAND_INLISTPASSIVETARGET;
  pn532_packetbuffer[1] = 1;
  pn532_packetbuffer[2] = 0;
#ifdef PN532DEBUG
    Serial.print("About to inList passive target");
#endif

  if (!sendCommandCheckAck(pn532_packetbuffer,3,1000)) {
#ifdef PN532DEBUG
      Serial.println("Could not send inlist message");
#endif
    return false;
  }

  if (!waitUntilReady(30000)) {
    return false;
  }

  wirereaddata(pn532_packetbuffer,sizeof(pn532_packetbuffer));
  
  if (pn532_packetbuffer[0] == 0 && pn532_packetbuffer[1] == 0 && pn532_packetbuffer[2] == 0xff) {
    uint8_t length = pn532_packetbuffer[3];
    if (pn532_packetbuffer[4]!=(uint8_t)(~length+1)) {
#ifdef PN532DEBUG
        Serial.println("Length check invalid");
        Serial.println(length,HEX);
        Serial.println((~length)+1,HEX);
#endif
      return false;
    }
    if (pn532_packetbuffer[5]==PN532_PN532TOHOST && pn532_packetbuffer[6]==PN532_RESPONSE_INLISTPASSIVETARGET) {
      if (pn532_packetbuffer[7] != 1) {
#ifdef PN532DEBUG
        Serial.println("Unhandled number of targets inlisted");
#endif
        Serial.println("Number of tags inlisted:");
        Serial.println(pn532_packetbuffer[7]);
        return false;
      }
      
      inListedTag = pn532_packetbuffer[8];
      Serial.print("Tag number: ");
      Serial.println(inListedTag);
      
      return true;
    } else {
#ifdef PN532DEBUG
        Serial.print("Unexpected response to inlist passive host");
#endif
      return false;
    }
  }
  else {
#ifdef PN532DEBUG
      Serial.println("Preamble missing");
#endif
    return false;
  }

  return true;
}
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