text: /**
   * MFRC522.h - Library to use ARDUINO RFID MODULE KIT 13.56 MHZ WITH TAGS SPI W AND R BY COOQROBOT.
   * Based on code Dr.Leong   ( WWW.B2CQSHOP.COM )
   * Created by Miguel Balboa (circuitito.com), Jan, 2012.
   * Rewritten by Søren Thing Andersen (access.thing.dk), fall of 2013 (Translation to English, refactored, comments, anti collision, cascade levels.)
   * Extended by Tom Clement with functionality to write to sector 0 of UID changeable Mifare cards.
   * Released into the public domain.
   * 
   * Please read this file for an overview and then MFRC522.cpp for comments on the specific functions.
   * Search for "mf-rc522" on ebay.com to purchase the MF-RC522 board. 
   * 
   * There are three hardware components involved:
   * 1) The micro controller: An Arduino
   * 2) The PCD (short for Proximity Coupling Device): NXP MFRC522 Contactless Reader IC
   * 3) The PICC (short for Proximity Integrated Circuit Card): A card or tag using the ISO 14443A interface, eg Mifare or NTAG203.
   * 
   * The microcontroller and card reader uses SPI for communication.
   * The protocol is described in the MFRC522 datasheet: http://www.nxp.com/documents/data_sheet/MFRC522.pdf
   * 
   * The card reader and the tags communicate using a 13.56MHz electromagnetic field.
   * The protocol is defined in ISO/IEC 14443-3 Identification cards -- Contactless integrated circuit cards -- Proximity cards -- Part 3: Initialization and anticollision".
   * A free version of the final draft can be found at http://wg8.de/wg8n1496_17n3613_Ballot_FCD14443-3.pdf
   * Details are found in chapter 6, Type A – Initialization and anticollision.
   * 
   * If only the PICC UID is wanted, the above documents has all the needed information.
   * To read and write from MIFARE PICCs, the MIFARE protocol is used after the PICC has been selected.
   * The MIFARE Classic chips and protocol is described in the datasheets:
   *		1K:   http://www.mouser.com/ds/2/302/MF1S503x-89574.pdf
   * 		4K:   http://datasheet.octopart.com/MF1S7035DA4,118-NXP-Semiconductors-datasheet-11046188.pdf
   * 		Mini: http://www.idcardmarket.com/download/mifare_S20_datasheet.pdf
   * The MIFARE Ultralight chip and protocol is described in the datasheets:
   *		Ultralight:   http://www.nxp.com/documents/data_sheet/MF0ICU1.pdf
   * 		Ultralight C: http://www.nxp.com/documents/short_data_sheet/MF0ICU2_SDS.pdf
   * 
   * MIFARE Classic 1K (MF1S503x):
   * 		Has 16 sectors * 4 blocks/sector * 16 bytes/block = 1024 bytes.
   * 		The blocks are numbered 0-63.
   * 		Block 3 in each sector is the Sector Trailer. See http://www.mouser.com/ds/2/302/MF1S503x-89574.pdf sections 8.6 and 8.7:
   * 				Bytes 0-5:   Key A
   * 				Bytes 6-8:   Access Bits
   * 				Bytes 9:     User data
   * 				Bytes 10-15: Key B (or user data)
   * 		Block 0 is read-only manufacturer data.
   * 		To access a block, an authentication using a key from the block's sector must be performed first.
   * 		Example: To read from block 10, first authenticate using a key from sector 3 (blocks 8-11).
   * 		All keys are set to FFFFFFFFFFFFh at chip delivery.
   * 		Warning: Please read section 8.7 "Memory Access". It includes this text: if the PICC detects a format violation the whole sector is irreversibly blocked.
   *		To use a block in "value block" mode (for Increment/Decrement operations) you need to change the sector trailer. Use PICC_SetAccessBits() to calculate the bit patterns.
   * MIFARE Classic 4K (MF1S703x):
   * 		Has (32 sectors * 4 blocks/sector + 8 sectors * 16 blocks/sector) * 16 bytes/block = 4096 bytes.
   * 		The blocks are numbered 0-255.
   * 		The last block in each sector is the Sector Trailer like above.
   * MIFARE Classic Mini (MF1 IC S20):
   * 		Has 5 sectors * 4 blocks/sector * 16 bytes/block = 320 bytes.
   * 		The blocks are numbered 0-19.
   * 		The last block in each sector is the Sector Trailer like above.
   * 
   * MIFARE Ultralight (MF0ICU1):
   * 		Has 16 pages of 4 bytes = 64 bytes.
   * 		Pages 0 + 1 is used for the 7-byte UID.
   * 		Page 2 contains the last check digit for the UID, one byte manufacturer internal data, and the lock bytes (see http://www.nxp.com/documents/data_sheet/MF0ICU1.pdf section 8.5.2)
   * 		Page 3 is OTP, One Time Programmable bits. Once set to 1 they cannot revert to 0.
   * 		Pages 4-15 are read/write unless blocked by the lock bytes in page 2. 
   * MIFARE Ultralight C (MF0ICU2):
   * 		Has 48 pages of 4 bytes = 192 bytes.
   * 		Pages 0 + 1 is used for the 7-byte UID.
   * 		Page 2 contains the last check digit for the UID, one byte manufacturer internal data, and the lock bytes (see http://www.nxp.com/documents/data_sheet/MF0ICU1.pdf section 8.5.2)
   * 		Page 3 is OTP, One Time Programmable bits. Once set to 1 they cannot revert to 0.
   * 		Pages 4-39 are read/write unless blocked by the lock bytes in page 2. 
   * 		Page 40 Lock bytes
   * 		Page 41 16 bit one way counter
   * 		Pages 42-43 Authentication configuration
   * 		Pages 44-47 Authentication key 
   */
  #ifndef MFRC522_h
  #define MFRC522_h
  
  #include "deprecated.h"
  // Enable integer limits
  #define __STDC_LIMIT_MACROS
  #include <stdint.h>
  #include <string>
  #include "Arduino.h"
  
  #ifndef MFRC522_SPICLOCK
  #define MFRC522_SPICLOCK BCM2835_SPI_CLOCK_DIVIDER_64			// MFRC522 accept upto 10MHz
  #endif
  
  // Firmware data for self-test
  // Reference values based on firmware version
  // Hint: if needed, you can remove unused self-test data to save flash memory
  //
  // Version 0.0 (0x90)
  // Philips Semiconductors; Preliminary Specification Revision 2.0 - 01 August 2005; 16.1 self-test
  const byte MFRC522_firmware_referenceV0_0[] = {
  	0x00, 0x87, 0x98, 0x0f, 0x49, 0xFF, 0x07, 0x19,
  	0xBF, 0x22, 0x30, 0x49, 0x59, 0x63, 0xAD, 0xCA,
  	0x7F, 0xE3, 0x4E, 0x03, 0x5C, 0x4E, 0x49, 0x50,
  	0x47, 0x9A, 0x37, 0x61, 0xE7, 0xE2, 0xC6, 0x2E,
  	0x75, 0x5A, 0xED, 0x04, 0x3D, 0x02, 0x4B, 0x78,
  	0x32, 0xFF, 0x58, 0x3B, 0x7C, 0xE9, 0x00, 0x94,
  	0xB4, 0x4A, 0x59, 0x5B, 0xFD, 0xC9, 0x29, 0xDF,
  	0x35, 0x96, 0x98, 0x9E, 0x4F, 0x30, 0x32, 0x8D
  };
  // Version 1.0 (0x91)
  // NXP Semiconductors; Rev. 3.8 - 17 September 2014; 16.1.1 self-test
  const byte MFRC522_firmware_referenceV1_0[] = {
  	0x00, 0xC6, 0x37, 0xD5, 0x32, 0xB7, 0x57, 0x5C,
  	0xC2, 0xD8, 0x7C, 0x4D, 0xD9, 0x70, 0xC7, 0x73,
  	0x10, 0xE6, 0xD2, 0xAA, 0x5E, 0xA1, 0x3E, 0x5A,
  	0x14, 0xAF, 0x30, 0x61, 0xC9, 0x70, 0xDB, 0x2E,
  	0x64, 0x22, 0x72, 0xB5, 0xBD, 0x65, 0xF4, 0xEC,
  	0x22, 0xBC, 0xD3, 0x72, 0x35, 0xCD, 0xAA, 0x41,
  	0x1F, 0xA7, 0xF3, 0x53, 0x14, 0xDE, 0x7E, 0x02,
  	0xD9, 0x0F, 0xB5, 0x5E, 0x25, 0x1D, 0x29, 0x79
  };
  // Version 2.0 (0x92)
  // NXP Semiconductors; Rev. 3.8 - 17 September 2014; 16.1.1 self-test
  const byte MFRC522_firmware_referenceV2_0[] = {
  	0x00, 0xEB, 0x66, 0xBA, 0x57, 0xBF, 0x23, 0x95,
  	0xD0, 0xE3, 0x0D, 0x3D, 0x27, 0x89, 0x5C, 0xDE,
  	0x9D, 0x3B, 0xA7, 0x00, 0x21, 0x5B, 0x89, 0x82,
  	0x51, 0x3A, 0xEB, 0x02, 0x0C, 0xA5, 0x00, 0x49,
  	0x7C, 0x84, 0x4D, 0xB3, 0xCC, 0xD2, 0x1B, 0x81,
  	0x5D, 0x48, 0x76, 0xD5, 0x71, 0x61, 0x21, 0xA9,
  	0x86, 0x96, 0x83, 0x38, 0xCF, 0x9D, 0x5B, 0x6D,
  	0xDC, 0x15, 0xBA, 0x3E, 0x7D, 0x95, 0x3B, 0x2F
  };
  // Clone
  // Fudan Semiconductor FM17522 (0x88)
  const byte FM17522_firmware_reference[] = {
  	0x00, 0xD6, 0x78, 0x8C, 0xE2, 0xAA, 0x0C, 0x18,
  	0x2A, 0xB8, 0x7A, 0x7F, 0xD3, 0x6A, 0xCF, 0x0B,
  	0xB1, 0x37, 0x63, 0x4B, 0x69, 0xAE, 0x91, 0xC7,
  	0xC3, 0x97, 0xAE, 0x77, 0xF4, 0x37, 0xD7, 0x9B,
  	0x7C, 0xF5, 0x3C, 0x11, 0x8F, 0x15, 0xC3, 0xD7,
  	0xC1, 0x5B, 0x00, 0x2A, 0xD0, 0x75, 0xDE, 0x9E,
  	0x51, 0x64, 0xAB, 0x3E, 0xE9, 0x15, 0xB5, 0xAB,
  	0x56, 0x9A, 0x98, 0x82, 0x26, 0xEA, 0x2A, 0x62
  };
  
  class MFRC522 {
  public:
  	// Size of the MFRC522 FIFO
  	static constexpr byte FIFO_SIZE = 64;		// The FIFO is 64 bytes.
  	// Default value for unused pin
  	static constexpr uint8_t UNUSED_PIN = UINT8_MAX;
  
  	// MFRC522 registers. Described in chapter 9 of the datasheet.
  	// When using SPI all addresses are shifted one bit left in the "SPI address byte" (section 8.1.2.3)
  	enum PCD_Register : byte {
  		// Page 0: Command and status
  		//						  0x00			// reserved for future use
  		CommandReg				= 0x01 << 1,	// starts and stops command execution
  		ComIEnReg				= 0x02 << 1,	// enable and disable interrupt request control bits
  		DivIEnReg				= 0x03 << 1,	// enable and disable interrupt request control bits
  		ComIrqReg				= 0x04 << 1,	// interrupt request bits
  		DivIrqReg				= 0x05 << 1,	// interrupt request bits
  		ErrorReg				= 0x06 << 1,	// error bits showing the error status of the last command executed 
  		Status1Reg				= 0x07 << 1,	// communication status bits
  		Status2Reg				= 0x08 << 1,	// receiver and transmitter status bits
  		FIFODataReg				= 0x09 << 1,	// input and output of 64 byte FIFO buffer
  		FIFOLevelReg			= 0x0A << 1,	// number of bytes stored in the FIFO buffer
  		WaterLevelReg			= 0x0B << 1,	// level for FIFO underflow and overflow warning
  		ControlReg				= 0x0C << 1,	// miscellaneous control registers
  		BitFramingReg			= 0x0D << 1,	// adjustments for bit-oriented frames
  		CollReg					= 0x0E << 1,	// bit position of the first bit-collision detected on the RF interface
  		//						  0x0F			// reserved for future use
  		
  		// Page 1: Command
  		// 						  0x10			// reserved for future use
  		ModeReg					= 0x11 << 1,	// defines general modes for transmitting and receiving 
  		TxModeReg				= 0x12 << 1,	// defines transmission data rate and framing
  		RxModeReg				= 0x13 << 1,	// defines reception data rate and framing
  		TxControlReg			= 0x14 << 1,	// controls the logical behavior of the antenna driver pins TX1 and TX2
  		TxASKReg				= 0x15 << 1,	// controls the setting of the transmission modulation
  		TxSelReg				= 0x16 << 1,	// selects the internal sources for the antenna driver
  		RxSelReg				= 0x17 << 1,	// selects internal receiver settings
  		RxThresholdReg			= 0x18 << 1,	// selects thresholds for the bit decoder
  		DemodReg				= 0x19 << 1,	// defines demodulator settings
  		// 						  0x1A			// reserved for future use
  		// 						  0x1B			// reserved for future use
  		MfTxReg					= 0x1C << 1,	// controls some MIFARE communication transmit parameters
  		MfRxReg					= 0x1D << 1,	// controls some MIFARE communication receive parameters
  		// 						  0x1E			// reserved for future use
  		SerialSpeedReg			= 0x1F << 1,	// selects the speed of the serial UART interface
  		
  		// Page 2: Configuration
  		// 						  0x20			// reserved for future use
  		CRCResultRegH			= 0x21 << 1,	// shows the MSB and LSB values of the CRC calculation
  		CRCResultRegL			= 0x22 << 1,
  		// 						  0x23			// reserved for future use
  		ModWidthReg				= 0x24 << 1,	// controls the ModWidth setting?
  		// 						  0x25			// reserved for future use
  		RFCfgReg				= 0x26 << 1,	// configures the receiver gain
  		GsNReg					= 0x27 << 1,	// selects the conductance of the antenna driver pins TX1 and TX2 for modulation 
  		CWGsPReg				= 0x28 << 1,	// defines the conductance of the p-driver output during periods of no modulation
  		ModGsPReg				= 0x29 << 1,	// defines the conductance of the p-driver output during periods of modulation
  		TModeReg				= 0x2A << 1,	// defines settings for the internal timer
  		TPrescalerReg			= 0x2B << 1,	// the lower 8 bits of the TPrescaler value. The 4 high bits are in TModeReg.
  		TReloadRegH				= 0x2C << 1,	// defines the 16-bit timer reload value
  		TReloadRegL				= 0x2D << 1,
  		TCounterValueRegH		= 0x2E << 1,	// shows the 16-bit timer value
  		TCounterValueRegL		= 0x2F << 1,
  		
  		// Page 3: Test Registers
  		// 						  0x30			// reserved for future use
  		TestSel1Reg				= 0x31 << 1,	// general test signal configuration
  		TestSel2Reg				= 0x32 << 1,	// general test signal configuration
  		TestPinEnReg			= 0x33 << 1,	// enables pin output driver on pins D1 to D7
  		TestPinValueReg			= 0x34 << 1,	// defines the values for D1 to D7 when it is used as an I/O bus
  		TestBusReg				= 0x35 << 1,	// shows the status of the internal test bus
  		AutoTestReg				= 0x36 << 1,	// controls the digital self-test
  		VersionReg				= 0x37 << 1,	// shows the software version
  		AnalogTestReg			= 0x38 << 1,	// controls the pins AUX1 and AUX2
  		TestDAC1Reg				= 0x39 << 1,	// defines the test value for TestDAC1
  		TestDAC2Reg				= 0x3A << 1,	// defines the test value for TestDAC2
  		TestADCReg				= 0x3B << 1		// shows the value of ADC I and Q channels
  		// 						  0x3C			// reserved for production tests
  		// 						  0x3D			// reserved for production tests
  		// 						  0x3E			// reserved for production tests
  		// 						  0x3F			// reserved for production tests
  	};
  	
  	// MFRC522 commands. Described in chapter 10 of the datasheet.
  	enum PCD_Command : byte {
  		PCD_Idle				= 0x00,		// no action, cancels current command execution
  		PCD_Mem					= 0x01,		// stores 25 bytes into the internal buffer
  		PCD_GenerateRandomID	= 0x02,		// generates a 10-byte random ID number
  		PCD_CalcCRC				= 0x03,		// activates the CRC coprocessor or performs a self-test
  		PCD_Transmit			= 0x04,		// transmits data from the FIFO buffer
  		PCD_NoCmdChange			= 0x07,		// no command change, can be used to modify the CommandReg register bits without affecting the command, for example, the PowerDown bit
  		PCD_Receive				= 0x08,		// activates the receiver circuits
  		PCD_Transceive 			= 0x0C,		// transmits data from FIFO buffer to antenna and automatically activates the receiver after transmission
  		PCD_MFAuthent 			= 0x0E,		// performs the MIFARE standard authentication as a reader
  		PCD_SoftReset			= 0x0F		// resets the MFRC522
  	};
  	
  	// MFRC522 RxGain[2:0] masks, defines the receiver's signal voltage gain factor (on the PCD).
  	// Described in 9.3.3.6 / table 98 of the datasheet at http://www.nxp.com/documents/data_sheet/MFRC522.pdf
  	enum PCD_RxGain : byte {
  		RxGain_18dB				= 0x00 << 4,	// 000b - 18 dB, minimum
  		RxGain_23dB				= 0x01 << 4,	// 001b - 23 dB
  		RxGain_18dB_2			= 0x02 << 4,	// 010b - 18 dB, it seems 010b is a duplicate for 000b
  		RxGain_23dB_2			= 0x03 << 4,	// 011b - 23 dB, it seems 011b is a duplicate for 001b
  		RxGain_33dB				= 0x04 << 4,	// 100b - 33 dB, average, and typical default
  		RxGain_38dB				= 0x05 << 4,	// 101b - 38 dB
  		RxGain_43dB				= 0x06 << 4,	// 110b - 43 dB
  		RxGain_48dB				= 0x07 << 4,	// 111b - 48 dB, maximum
  		RxGain_min				= 0x00 << 4,	// 000b - 18 dB, minimum, convenience for RxGain_18dB
  		RxGain_avg				= 0x04 << 4,	// 100b - 33 dB, average, convenience for RxGain_33dB
  		RxGain_max				= 0x07 << 4		// 111b - 48 dB, maximum, convenience for RxGain_48dB
  	};
  	
  	// Commands sent to the PICC.
  	enum PICC_Command : byte {
  		// The commands used by the PCD to manage communication with several PICCs (ISO 14443-3, Type A, section 6.4)
  		PICC_CMD_REQA			= 0x26,		// REQuest command, Type A. Invites PICCs in state IDLE to go to READY and prepare for anticollision or selection. 7 bit frame.
  		PICC_CMD_WUPA			= 0x52,		// Wake-UP command, Type A. Invites PICCs in state IDLE and HALT to go to READY(*) and prepare for anticollision or selection. 7 bit frame.
  		PICC_CMD_CT				= 0x88,		// Cascade Tag. Not really a command, but used during anti collision.
  		PICC_CMD_SEL_CL1		= 0x93,		// Anti collision/Select, Cascade Level 1
  		PICC_CMD_SEL_CL2		= 0x95,		// Anti collision/Select, Cascade Level 2
  		PICC_CMD_SEL_CL3		= 0x97,		// Anti collision/Select, Cascade Level 3
  		PICC_CMD_HLTA			= 0x50,		// HaLT command, Type A. Instructs an ACTIVE PICC to go to state HALT.
  		PICC_CMD_RATS           = 0xE0,     // Request command for Answer To Reset.
  		// The commands used for MIFARE Classic (from http://www.mouser.com/ds/2/302/MF1S503x-89574.pdf, Section 9)
  		// Use PCD_MFAuthent to authenticate access to a sector, then use these commands to read/write/modify the blocks on the sector.
  		// The read/write commands can also be used for MIFARE Ultralight.
  		PICC_CMD_MF_AUTH_KEY_A	= 0x60,		// Perform authentication with Key A
  		PICC_CMD_MF_AUTH_KEY_B	= 0x61,		// Perform authentication with Key B
  		PICC_CMD_MF_READ		= 0x30,		// Reads one 16 byte block from the authenticated sector of the PICC. Also used for MIFARE Ultralight.
  		PICC_CMD_MF_WRITE		= 0xA0,		// Writes one 16 byte block to the authenticated sector of the PICC. Called "COMPATIBILITY WRITE" for MIFARE Ultralight.
  		PICC_CMD_MF_DECREMENT	= 0xC0,		// Decrements the contents of a block and stores the result in the internal data register.
  		PICC_CMD_MF_INCREMENT	= 0xC1,		// Increments the contents of a block and stores the result in the internal data register.
  		PICC_CMD_MF_RESTORE		= 0xC2,		// Reads the contents of a block into the internal data register.
  		PICC_CMD_MF_TRANSFER	= 0xB0,		// Writes the contents of the internal data register to a block.
  		// The commands used for MIFARE Ultralight (from http://www.nxp.com/documents/data_sheet/MF0ICU1.pdf, Section 8.6)
  		// The PICC_CMD_MF_READ and PICC_CMD_MF_WRITE can also be used for MIFARE Ultralight.
  		PICC_CMD_UL_WRITE		= 0xA2		// Writes one 4 byte page to the PICC.
  	};
  	
  	// MIFARE constants that does not fit anywhere else
  	enum MIFARE_Misc {
  		MF_ACK					= 0xA,		// The MIFARE Classic uses a 4 bit ACK/NAK. Any other value than 0xA is NAK.
  		MF_KEY_SIZE				= 6			// A Mifare Crypto1 key is 6 bytes.
  	};
  	
  	// PICC types we can detect. Remember to update PICC_GetTypeName() if you add more.
  	// last value set to 0xff, then compiler uses less ram, it seems some optimisations are triggered
  	enum PICC_Type : byte {
  		PICC_TYPE_UNKNOWN		,
  		PICC_TYPE_ISO_14443_4	,	// PICC compliant with ISO/IEC 14443-4 
  		PICC_TYPE_ISO_18092		, 	// PICC compliant with ISO/IEC 18092 (NFC)
  		PICC_TYPE_MIFARE_MINI	,	// MIFARE Classic protocol, 320 bytes
  		PICC_TYPE_MIFARE_1K		,	// MIFARE Classic protocol, 1KB
  		PICC_TYPE_MIFARE_4K		,	// MIFARE Classic protocol, 4KB
  		PICC_TYPE_MIFARE_UL		,	// MIFARE Ultralight or Ultralight C
  		PICC_TYPE_MIFARE_PLUS	,	// MIFARE Plus
  		PICC_TYPE_MIFARE_DESFIRE,	// MIFARE DESFire
  		PICC_TYPE_TNP3XXX		,	// Only mentioned in NXP AN 10833 MIFARE Type Identification Procedure
  		PICC_TYPE_NOT_COMPLETE	= 0xff	// SAK indicates UID is not complete.
  	};
  	
  	// Return codes from the functions in this class. Remember to update GetStatusCodeName() if you add more.
  	// last value set to 0xff, then compiler uses less ram, it seems some optimisations are triggered
  	enum StatusCode : byte {
  		STATUS_OK				,	// Success
  		STATUS_ERROR			,	// Error in communication
  		STATUS_COLLISION		,	// Collission detected
  		STATUS_TIMEOUT			,	// Timeout in communication.
  		STATUS_NO_ROOM			,	// A buffer is not big enough.
  		STATUS_INTERNAL_ERROR	,	// Internal error in the code. Should not happen ;-)
  		STATUS_INVALID			,	// Invalid argument.
  		STATUS_CRC_WRONG		,	// The CRC_A does not match
  		STATUS_MIFARE_NACK		= 0xff	// A MIFARE PICC responded with NAK.
  	};
  	
  	// A struct used for passing the UID of a PICC.
  	typedef struct {
  		byte		size;			// Number of bytes in the UID. 4, 7 or 10.
  		byte		uidByte[10];
  		byte		sak;			// The SAK (Select acknowledge) byte returned from the PICC after successful selection.
  	} Uid;
  
  	// A struct used for passing a MIFARE Crypto1 key
  	typedef struct {
  		byte		keyByte[MF_KEY_SIZE];
  	} MIFARE_Key;
  	
  	// Member variables
  	Uid uid;								// Used by PICC_ReadCardSerial().
  	
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Functions for setting up the Arduino
  	/////////////////////////////////////////////////////////////////////////////////////
  	MFRC522();
  	MFRC522(byte chipSelectPin, byte resetPowerDownPin);
  	
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Basic interface functions for communicating with the MFRC522
  	/////////////////////////////////////////////////////////////////////////////////////
  	void PCD_WriteRegister(PCD_Register reg, byte value);
  	void PCD_WriteRegister(PCD_Register reg, byte count, byte *values);
  	byte PCD_ReadRegister(PCD_Register reg);
  	void PCD_ReadRegister(PCD_Register reg, byte count, byte *values, byte rxAlign = 0);
  	void PCD_SetRegisterBitMask(PCD_Register reg, byte mask);
  	void PCD_ClearRegisterBitMask(PCD_Register reg, byte mask);
  	StatusCode PCD_CalculateCRC(byte *data, byte length, byte *result);
  	
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Functions for manipulating the MFRC522
  	/////////////////////////////////////////////////////////////////////////////////////
  	void PCD_Init();
  	void PCD_Init(byte chipSelectPin, byte resetPowerDownPin);
  	void PCD_Reset();
  	void PCD_AntennaOn();
  	void PCD_AntennaOff();
  	byte PCD_GetAntennaGain();
  	void PCD_SetAntennaGain(byte mask);
  	bool PCD_PerformSelfTest();
  	
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Power control functions
  	/////////////////////////////////////////////////////////////////////////////////////
  	void PCD_SoftPowerDown();
  	void PCD_SoftPowerUp();
  	
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Functions for communicating with PICCs
  	/////////////////////////////////////////////////////////////////////////////////////
  	StatusCode PCD_TransceiveData(byte *sendData, byte sendLen, byte *backData, byte *backLen, byte *validBits = nullptr, byte rxAlign = 0, bool checkCRC = false);
  	StatusCode PCD_CommunicateWithPICC(byte command, byte waitIRq, byte *sendData, byte sendLen, byte *backData = nullptr, byte *backLen = nullptr, byte *validBits = nullptr, byte rxAlign = 0, bool checkCRC = false);
  	StatusCode PICC_RequestA(byte *bufferATQA, byte *bufferSize);
  	StatusCode PICC_WakeupA(byte *bufferATQA, byte *bufferSize);
  	StatusCode PICC_REQA_or_WUPA(byte command, byte *bufferATQA, byte *bufferSize);
  	virtual StatusCode PICC_Select(Uid *uid, byte validBits = 0);
  	StatusCode PICC_HaltA();
  
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Functions for communicating with MIFARE PICCs
  	/////////////////////////////////////////////////////////////////////////////////////
  	StatusCode PCD_Authenticate(byte command, byte blockAddr, MIFARE_Key *key, Uid *uid);
  	void PCD_StopCrypto1();
  	StatusCode MIFARE_Read(byte blockAddr, byte *buffer, byte *bufferSize);
  	StatusCode MIFARE_Write(byte blockAddr, byte *buffer, byte bufferSize);
  	StatusCode MIFARE_Ultralight_Write(byte page, byte *buffer, byte bufferSize);
  	StatusCode MIFARE_Decrement(byte blockAddr, int32_t delta);
  	StatusCode MIFARE_Increment(byte blockAddr, int32_t delta);
  	StatusCode MIFARE_Restore(byte blockAddr);
  	StatusCode MIFARE_Transfer(byte blockAddr);
  	StatusCode MIFARE_GetValue(byte blockAddr, int32_t *value);
  	StatusCode MIFARE_SetValue(byte blockAddr, int32_t value);
  	StatusCode PCD_NTAG216_AUTH(byte *passWord, byte pACK[]);
  	
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Support functions
  	/////////////////////////////////////////////////////////////////////////////////////
  	StatusCode PCD_MIFARE_Transceive(byte *sendData, byte sendLen, bool acceptTimeout = false);
  	// old function used too much memory, now name moved to flash; if you need char, copy from flash to memory
  	//const char *GetStatusCodeName(byte code);
  	static std::string GetStatusCodeName(StatusCode code);
  	static PICC_Type PICC_GetType(byte sak);
  	// old function used too much memory, now name moved to flash; if you need char, copy from flash to memory
  	//const char *PICC_GetTypeName(byte type);
  	static std::string PICC_GetTypeName(PICC_Type type);
  	
  	// Support functions for debuging
  	void PCD_DumpVersionToSerial();
  	void PICC_DumpToSerial(Uid *uid);
  	void PICC_DumpDetailsToSerial(Uid *uid);
  	void PICC_DumpMifareClassicToSerial(Uid *uid, PICC_Type piccType, MIFARE_Key *key);
  	void PICC_DumpMifareClassicSectorToSerial(Uid *uid, MIFARE_Key *key, byte sector);
  	void PICC_DumpMifareUltralightToSerial();
  	
  	// Advanced functions for MIFARE
  	// DEPRECATED_MSG("name will change in next version")
  	void MIFARE_SetAccessBits(byte *accessBitBuffer, byte g0, byte g1, byte g2, byte g3);
  	// DEPRECATED_MSG("will move to extra class in next version")
  	bool MIFARE_OpenUidBackdoor(bool logErrors);
  	// DEPRECATED_MSG("will move to extra class in next version")
  	bool MIFARE_SetUid(byte *newUid, byte uidSize, bool logErrors);
  	// DEPRECATED_MSG("will move to extra class in next version")
  	bool MIFARE_UnbrickUidSector(bool logErrors);
  	
  	/////////////////////////////////////////////////////////////////////////////////////
  	// Convenience functions - does not add extra functionality
  	/////////////////////////////////////////////////////////////////////////////////////
  	virtual bool PICC_IsNewCardPresent();
  	virtual bool PICC_ReadCardSerial();
  	virtual bool PICC_IsCardPresent();
  	
  protected:
  	byte _chipSelectPin;		// Arduino pin connected to MFRC522's SPI slave select input (Pin 24, NSS, active low)
  	byte _resetPowerDownPin;	// Arduino pin connected to MFRC522's reset and power down input (Pin 6, NRSTPD, active low)
  	StatusCode MIFARE_TwoStepHelper(byte command, byte blockAddr, int32_t data);
  };
  
  #endif
  