Martin Olejar
MFRC522 example project for FRDM
Diff: MFRC522.cpp
- Revision:
- 0:1d9c7c0b5015
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/MFRC522.cpp Sat Dec 14 21:41:08 2013 +0000
@@ -0,0 +1,1189 @@
+/*
+* MFRC522.cpp - Library to use ARDUINO RFID MODULE KIT 13.56 MHZ WITH TAGS SPI W AND R BY COOQROBOT.
+* _Please_ see the comments in MFRC522.h - they give useful hints and background.
+* Released into the public domain.
+*/
+
+#include "MFRC522.h"
+
+
+#define MFRC522_MaxPICCs 9
+#define MFRC522_MaxError 10
+
+static std::string _TypeNamePICC[MFRC522_MaxPICCs] =
+{
+ "Unknown type",
+ "PICC compliant with ISO/IEC 14443-4",
+ "PICC compliant with ISO/IEC 18092 (NFC)",
+ "MIFARE Mini, 320 bytes",
+ "MIFARE 1KB",
+ "MIFARE 4KB",
+ "MIFARE Ultralight or Ultralight C",
+ "MIFARE Plus",
+ "MIFARE TNP3XXX"
+};
+
+static std::string _ErrorMessage[MFRC522_MaxError] =
+{
+ "Unknown error",
+ "Success",
+ "Error in communication",
+ "Collision detected",
+ "Timeout in communication",
+ "A buffer is not big enough",
+ "Internal error in the code, should not happen",
+ "Invalid argument",
+ "The CRC_A does not match",
+ "A MIFARE PICC responded with NAK"
+};
+
+/////////////////////////////////////////////////////////////////////////////////////
+// Functions for setting up the driver
+/////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Constructor.
+ * Prepares the output pins.
+ */
+MFRC522::MFRC522(PinName mosi,
+ PinName miso,
+ PinName sclk,
+ PinName cs,
+ PinName reset) : m_SPI(mosi, miso, sclk), m_CS(cs), m_RESET(reset)
+{
+ /* init MFRC522 SPI BUS */
+ m_SPI.format(8, 0);
+ m_SPI.frequency(8000000);
+
+ /* init MFRC522 SPI_CS pin */
+ m_CS = 1;
+
+ /* init MFRC522 RESET pin */
+ m_RESET = 1;
+} // End constructor
+
+
+/////////////////////////////////////////////////////////////////////////////////////
+// Basic interface functions for communicating with the MFRC522
+/////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Writes a byte to the specified register in the MFRC522 chip.
+ * The interface is described in the datasheet section 8.1.2.
+ */
+void MFRC522::PCD_WriteRegister(uint8_t reg, uint8_t value)
+{
+ m_CS = 0; /* Select SPI Chip MFRC522 */
+
+ // MSB == 0 is for writing. LSB is not used in address. Datasheet section 8.1.2.3.
+ (void) m_SPI.write(reg & 0x7E);
+ (void) m_SPI.write(value);
+
+ m_CS = 1; /* Release SPI Chip MFRC522 */
+} // End PCD_WriteRegister()
+
+/**
+ * Writes a number of bytes to the specified register in the MFRC522 chip.
+ * The interface is described in the datasheet section 8.1.2.
+ */
+void MFRC522::PCD_WriteRegister(uint8_t reg, uint8_t count, uint8_t *values)
+{
+ m_CS = 0; /* Select SPI Chip MFRC522 */
+
+ // MSB == 0 is for writing. LSB is not used in address. Datasheet section 8.1.2.3.
+ (void) m_SPI.write(reg & 0x7E);
+ for (uint8_t index = 0; index < count; index++)
+ {
+ (void) m_SPI.write(values[index]);
+ }
+
+ m_CS = 1; /* Release SPI Chip MFRC522 */
+} // End PCD_WriteRegister()
+
+/**
+ * Reads a byte from the specified register in the MFRC522 chip.
+ * The interface is described in the datasheet section 8.1.2.
+ */
+uint8_t MFRC522::PCD_ReadRegister(uint8_t reg)
+{
+ uint8_t value;
+ m_CS = 0; /* Select SPI Chip MFRC522 */
+
+ // MSB == 1 is for reading. LSB is not used in address. Datasheet section 8.1.2.3.
+ (void) m_SPI.write(0x80 | reg);
+ value = m_SPI.write(0); // Read the value back. Send 0 to stop reading.
+
+ m_CS = 1; /* Release SPI Chip MFRC522 */
+ return value;
+} // End PCD_ReadRegister()
+
+/**
+ * Reads a number of bytes from the specified register in the MFRC522 chip.
+ * The interface is described in the datasheet section 8.1.2.
+ */
+void MFRC522::PCD_ReadRegister(uint8_t reg, uint8_t count, uint8_t *values, uint8_t rxAlign)
+{
+ if (count == 0) { return; }
+
+ //Serial.print("Reading "); Serial.print(count); Serial.println(" bytes from register.");
+ uint8_t address = 0x80 | reg; // MSB == 1 is for reading. LSB is not used in address. Datasheet section 8.1.2.3.
+ uint8_t index = 0; // Index in values array.
+
+ m_CS = 0; /* Select SPI Chip MFRC522 */
+ count--; // One read is performed outside of the loop
+ (void) m_SPI.write(address); // Tell MFRC522 which address we want to read
+
+ while (index < count)
+ {
+ if ((index == 0) && rxAlign) // Only update bit positions rxAlign..7 in values[0]
+ {
+ // Create bit mask for bit positions rxAlign..7
+ uint8_t mask = 0;
+ for (uint8_t i = rxAlign; i <= 7; i++)
+ {
+ mask |= (1 << i);
+ }
+
+ // Read value and tell that we want to read the same address again.
+ uint8_t value = m_SPI.write(address);
+
+ // Apply mask to both current value of values[0] and the new data in value.
+ values[0] = (values[index] & ~mask) | (value & mask);
+ }
+ else
+ {
+ // Read value and tell that we want to read the same address again.
+ values[index] = m_SPI.write(address);
+ }
+
+ index++;
+ }
+
+ values[index] = m_SPI.write(0); // Read the final byte. Send 0 to stop reading.
+
+ m_CS = 1; /* Release SPI Chip MFRC522 */
+} // End PCD_ReadRegister()
+
+/**
+ * Sets the bits given in mask in register reg.
+ */
+void MFRC522::PCD_SetRegisterBitMask(uint8_t reg, uint8_t mask)
+{
+ uint8_t tmp;
+ tmp = PCD_ReadRegister(reg);
+ PCD_WriteRegister(reg, tmp | mask); // set bit mask
+} // End PCD_SetRegisterBitMask()
+
+/**
+ * Clears the bits given in mask from register reg.
+ */
+void MFRC522::PCD_ClearRegisterBitMask(uint8_t reg, uint8_t mask)
+{
+ uint8_t tmp;
+ tmp = PCD_ReadRegister(reg);
+ PCD_WriteRegister(reg, tmp & (~mask)); // clear bit mask
+} // End PCD_ClearRegisterBitMask()
+
+
+/**
+ * Use the CRC coprocessor in the MFRC522 to calculate a CRC_A.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PCD_CalculateCRC(uint8_t *data, uint8_t length, uint8_t *result)
+{
+ PCD_WriteRegister(CommandReg, PCD_Idle); // Stop any active command.
+ PCD_WriteRegister(DivIrqReg, 0x04); // Clear the CRCIRq interrupt request bit
+ PCD_SetRegisterBitMask(FIFOLevelReg, 0x80); // FlushBuffer = 1, FIFO initialization
+ PCD_WriteRegister(FIFODataReg, length, data); // Write data to the FIFO
+ PCD_WriteRegister(CommandReg, PCD_CalcCRC); // Start the calculation
+
+ // Wait for the CRC calculation to complete. Each iteration of the while-loop takes 17.73�s.
+ uint16_t i = 5000;
+ uint8_t n;
+ while (1)
+ {
+ n = PCD_ReadRegister(DivIrqReg); // DivIrqReg[7..0] bits are: Set2 reserved reserved MfinActIRq reserved CRCIRq reserved reserved
+ if (n & 0x04)
+ {
+ // CRCIRq bit set - calculation done
+ break;
+ }
+ if (--i == 0)
+ {
+ // The emergency break. We will eventually terminate on this one after 89ms.
+ // Communication with the MFRC522 might be down.
+ return STATUS_TIMEOUT;
+ }
+ }
+
+ // Stop calculating CRC for new content in the FIFO.
+ PCD_WriteRegister(CommandReg, PCD_Idle);
+
+ // Transfer the result from the registers to the result buffer
+ result[0] = PCD_ReadRegister(CRCResultRegL);
+ result[1] = PCD_ReadRegister(CRCResultRegH);
+ return STATUS_OK;
+} // End PCD_CalculateCRC()
+
+
+/////////////////////////////////////////////////////////////////////////////////////
+// Functions for manipulating the MFRC522
+/////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Initializes the MFRC522 chip.
+ */
+void MFRC522::PCD_Init()
+{
+ /* Reset MFRC522 */
+ m_RESET = 0;
+ wait_ms(10);
+ m_RESET = 1;
+ // Section 8.8.2 in the datasheet says the oscillator start-up time is the start up time of the crystal + 37,74�s. Let us be generous: 50ms.
+ wait_ms(50);
+
+ // When communicating with a PICC we need a timeout if something goes wrong.
+ // f_timer = 13.56 MHz / (2*TPreScaler+1) where TPreScaler = [TPrescaler_Hi:TPrescaler_Lo].
+ // TPrescaler_Hi are the four low bits in TModeReg. TPrescaler_Lo is TPrescalerReg.
+ PCD_WriteRegister(TModeReg, 0x80); // TAuto=1; timer starts automatically at the end of the transmission in all communication modes at all speeds
+ PCD_WriteRegister(TPrescalerReg, 0xA9); // TPreScaler = TModeReg[3..0]:TPrescalerReg, ie 0x0A9 = 169 => f_timer=40kHz, ie a timer period of 25�s.
+ PCD_WriteRegister(TReloadRegH, 0x03); // Reload timer with 0x3E8 = 1000, ie 25ms before timeout.
+ PCD_WriteRegister(TReloadRegL, 0xE8);
+
+ PCD_WriteRegister(TxASKReg, 0x40); // Default 0x00. Force a 100 % ASK modulation independent of the ModGsPReg register setting
+ PCD_WriteRegister(ModeReg, 0x3D); // Default 0x3F. Set the preset value for the CRC coprocessor for the CalcCRC command to 0x6363 (ISO 14443-3 part 6.2.4)
+ PCD_AntennaOn(); // Enable the antenna driver pins TX1 and TX2 (they were disabled by the reset)
+} // End PCD_Init()
+
+/**
+ * Performs a soft reset on the MFRC522 chip and waits for it to be ready again.
+ */
+void MFRC522::PCD_Reset()
+{
+ PCD_WriteRegister(CommandReg, PCD_SoftReset); // Issue the SoftReset command.
+ // The datasheet does not mention how long the SoftRest command takes to complete.
+ // But the MFRC522 might have been in soft power-down mode (triggered by bit 4 of CommandReg)
+ // Section 8.8.2 in the datasheet says the oscillator start-up time is the start up time of the crystal + 37,74�s. Let us be generous: 50ms.
+ wait_ms(50);
+
+ // Wait for the PowerDown bit in CommandReg to be cleared
+ while (PCD_ReadRegister(CommandReg) & (1<<4))
+ {
+ // PCD still restarting - unlikely after waiting 50ms, but better safe than sorry.
+ }
+} // End PCD_Reset()
+
+/**
+ * Turns the antenna on by enabling pins TX1 and TX2.
+ * After a reset these pins disabled.
+ */
+void MFRC522::PCD_AntennaOn()
+{
+ uint8_t value = PCD_ReadRegister(TxControlReg);
+ if ((value & 0x03) != 0x03)
+ {
+ PCD_WriteRegister(TxControlReg, value | 0x03);
+ }
+} // End PCD_AntennaOn()
+
+/////////////////////////////////////////////////////////////////////////////////////
+// Functions for communicating with PICCs
+/////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Executes the Transceive command.
+ * CRC validation can only be done if backData and backLen are specified.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PCD_TransceiveData(uint8_t *sendData, ///< Pointer to the data to transfer to the FIFO.
+ uint8_t sendLen, ///< Number of bytes to transfer to the FIFO.
+ uint8_t *backData, ///< NULL or pointer to buffer if data should be read back after executing the command.
+ uint8_t *backLen, ///< In: Max number of bytes to write to *backData. Out: The number of bytes returned.
+ uint8_t *validBits, ///< In/Out: The number of valid bits in the last byte. 0 for 8 valid bits. Default NULL.
+ uint8_t rxAlign, ///< In: Defines the bit position in backData[0] for the first bit received. Default 0.
+ bool checkCRC) ///< In: True => The last two bytes of the response is assumed to be a CRC_A that must be validated.
+{
+ uint8_t waitIRq = 0x30; // RxIRq and IdleIRq
+ return PCD_CommunicateWithPICC(PCD_Transceive, waitIRq, sendData, sendLen, backData, backLen, validBits, rxAlign, checkCRC);
+} // End PCD_TransceiveData()
+
+/**
+ * Transfers data to the MFRC522 FIFO, executes a commend, waits for completion and transfers data back from the FIFO.
+ * CRC validation can only be done if backData and backLen are specified.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PCD_CommunicateWithPICC(uint8_t command, ///< The command to execute. One of the PCD_Command enums.
+ uint8_t waitIRq, ///< The bits in the ComIrqReg register that signals successful completion of the command.
+ uint8_t *sendData, ///< Pointer to the data to transfer to the FIFO.
+ uint8_t sendLen, ///< Number of bytes to transfer to the FIFO.
+ uint8_t *backData, ///< NULL or pointer to buffer if data should be read back after executing the command.
+ uint8_t *backLen, ///< In: Max number of bytes to write to *backData. Out: The number of bytes returned.
+ uint8_t *validBits, ///< In/Out: The number of valid bits in the last byte. 0 for 8 valid bits.
+ uint8_t rxAlign, ///< In: Defines the bit position in backData[0] for the first bit received. Default 0.
+ bool checkCRC) ///< In: True => The last two bytes of the response is assumed to be a CRC_A that must be validated.
+{
+ uint8_t n, _validBits = 0;
+ uint32_t i;
+
+ // Prepare values for BitFramingReg
+ uint8_t txLastBits = validBits ? *validBits : 0;
+ uint8_t bitFraming = (rxAlign << 4) + txLastBits; // RxAlign = BitFramingReg[6..4]. TxLastBits = BitFramingReg[2..0]
+
+ PCD_WriteRegister(CommandReg, PCD_Idle); // Stop any active command.
+ PCD_WriteRegister(ComIrqReg, 0x7F); // Clear all seven interrupt request bits
+ PCD_SetRegisterBitMask(FIFOLevelReg, 0x80); // FlushBuffer = 1, FIFO initialization
+ PCD_WriteRegister(FIFODataReg, sendLen, sendData); // Write sendData to the FIFO
+ PCD_WriteRegister(BitFramingReg, bitFraming); // Bit adjustments
+ PCD_WriteRegister(CommandReg, command); // Execute the command
+ if (command == PCD_Transceive)
+ {
+ PCD_SetRegisterBitMask(BitFramingReg, 0x80); // StartSend=1, transmission of data starts
+ }
+
+ // Wait for the command to complete.
+ // In PCD_Init() we set the TAuto flag in TModeReg. This means the timer automatically starts when the PCD stops transmitting.
+ // Each iteration of the do-while-loop takes 17.86�s.
+ i = 2000;
+ while (1)
+ {
+ n = PCD_ReadRegister(ComIrqReg); // ComIrqReg[7..0] bits are: Set1 TxIRq RxIRq IdleIRq HiAlertIRq LoAlertIRq ErrIRq TimerIRq
+ if (n & waitIRq)
+ { // One of the interrupts that signal success has been set.
+ break;
+ }
+
+ if (n & 0x01)
+ { // Timer interrupt - nothing received in 25ms
+ return STATUS_TIMEOUT;
+ }
+
+ if (--i == 0)
+ { // The emergency break. If all other condions fail we will eventually terminate on this one after 35.7ms. Communication with the MFRC522 might be down.
+ return STATUS_TIMEOUT;
+ }
+ }
+
+ // Stop now if any errors except collisions were detected.
+ uint8_t errorRegValue = PCD_ReadRegister(ErrorReg); // ErrorReg[7..0] bits are: WrErr TempErr reserved BufferOvfl CollErr CRCErr ParityErr ProtocolErr
+ if (errorRegValue & 0x13)
+ { // BufferOvfl ParityErr ProtocolErr
+ return STATUS_ERROR;
+ }
+
+ // If the caller wants data back, get it from the MFRC522.
+ if (backData && backLen)
+ {
+ n = PCD_ReadRegister(FIFOLevelReg); // Number of bytes in the FIFO
+ if (n > *backLen)
+ {
+ return STATUS_NO_ROOM;
+ }
+
+ *backLen = n; // Number of bytes returned
+ PCD_ReadRegister(FIFODataReg, n, backData, rxAlign); // Get received data from FIFO
+ _validBits = PCD_ReadRegister(ControlReg) & 0x07; // RxLastBits[2:0] indicates the number of valid bits in the last received byte. If this value is 000b, the whole byte is valid.
+ if (validBits)
+ {
+ *validBits = _validBits;
+ }
+ }
+
+ // Tell about collisions
+ if (errorRegValue & 0x08) { // CollErr
+ return STATUS_COLLISION;
+ }
+
+ // Perform CRC_A validation if requested.
+ if (backData && backLen && checkCRC)
+ {
+ // In this case a MIFARE Classic NAK is not OK.
+ if (*backLen == 1 && _validBits == 4)
+ {
+ return STATUS_MIFARE_NACK;
+ }
+
+ // We need at least the CRC_A value and all 8 bits of the last byte must be received.
+ if (*backLen < 2 || _validBits != 0)
+ {
+ return STATUS_CRC_WRONG;
+ }
+
+ // Verify CRC_A - do our own calculation and store the control in controlBuffer.
+ uint8_t controlBuffer[2];
+ n = PCD_CalculateCRC(&backData[0], *backLen - 2, &controlBuffer[0]);
+ if (n != STATUS_OK)
+ {
+ return n;
+ }
+
+ if ((backData[*backLen - 2] != controlBuffer[0]) || (backData[*backLen - 1] != controlBuffer[1]))
+ {
+ return STATUS_CRC_WRONG;
+ }
+ }
+
+ return STATUS_OK;
+} // End PCD_CommunicateWithPICC()
+
+/**
+ * Transmits a REQuest command, Type A. Invites PICCs in state IDLE to go to READY and prepare for anticollision or selection. 7 bit frame.
+ * Beware: When two PICCs are in the field at the same time I often get STATUS_TIMEOUT - probably due do bad antenna design.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PICC_RequestA(uint8_t *bufferATQA, uint8_t *bufferSize)
+{
+ return PICC_REQA_or_WUPA(PICC_CMD_REQA, bufferATQA, bufferSize);
+} // End PICC_RequestA()
+
+/**
+ * Transmits a 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.
+ * Beware: When two PICCs are in the field at the same time I often get STATUS_TIMEOUT - probably due do bad antenna design.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PICC_WakeupA(uint8_t *bufferATQA, uint8_t *bufferSize)
+{
+ return PICC_REQA_or_WUPA(PICC_CMD_WUPA, bufferATQA, bufferSize);
+} // End PICC_WakeupA()
+
+/**
+ * Transmits REQA or WUPA commands.
+ * Beware: When two PICCs are in the field at the same time I often get STATUS_TIMEOUT - probably due do bad antenna design.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PICC_REQA_or_WUPA(uint8_t command, uint8_t *bufferATQA, uint8_t *bufferSize)
+{
+ uint8_t validBits;
+ uint8_t status;
+
+ if (bufferATQA == NULL || *bufferSize < 2) { // The ATQA response is 2 bytes long.
+ return STATUS_NO_ROOM;
+ }
+
+ PCD_ClearRegisterBitMask(CollReg, 0x80); // ValuesAfterColl=1 => Bits received after collision are cleared.
+ validBits = 7; // For REQA and WUPA we need the short frame format - transmit only 7 bits of the last (and only) byte. TxLastBits = BitFramingReg[2..0]
+ status = PCD_TransceiveData(&command, 1, bufferATQA, bufferSize, &validBits);
+ if (status != STATUS_OK)
+ {
+ return status;
+ }
+
+ if (*bufferSize != 2 || validBits != 0) { // ATQA must be exactly 16 bits.
+ return STATUS_ERROR;
+ }
+
+ return STATUS_OK;
+} // End PICC_REQA_or_WUPA()
+
+/**
+ * Transmits SELECT/ANTICOLLISION commands to select a single PICC.
+ * Before calling this function the PICCs must be placed in the READY(*) state by calling PICC_RequestA() or PICC_WakeupA().
+ * On success:
+ * - The chosen PICC is in state ACTIVE(*) and all other PICCs have returned to state IDLE/HALT. (Figure 7 of the ISO/IEC 14443-3 draft.)
+ * - The UID size and value of the chosen PICC is returned in *uid along with the SAK.
+ *
+ * A PICC UID consists of 4, 7 or 10 bytes.
+ * Only 4 bytes can be specified in a SELECT command, so for the longer UIDs two or three iterations are used:
+ * UID size Number of UID bytes Cascade levels Example of PICC
+ * ======== =================== ============== ===============
+ * single 4 1 MIFARE Classic
+ * double 7 2 MIFARE Ultralight
+ * triple 10 3 Not currently in use?
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PICC_Select(Uid *uid, uint8_t validBits)
+{
+ bool uidComplete;
+ bool selectDone;
+ bool useCascadeTag;
+ uint8_t cascadeLevel = 1;
+ uint8_t result;
+ uint8_t count;
+ uint8_t index;
+ uint8_t uidIndex; // The first index in uid->uidByte[] that is used in the current Cascade Level.
+ uint8_t currentLevelKnownBits; // The number of known UID bits in the current Cascade Level.
+ uint8_t buffer[9]; // The SELECT/ANTICOLLISION commands uses a 7 byte standard frame + 2 bytes CRC_A
+ uint8_t bufferUsed; // The number of bytes used in the buffer, ie the number of bytes to transfer to the FIFO.
+ uint8_t rxAlign; // Used in BitFramingReg. Defines the bit position for the first bit received.
+ uint8_t txLastBits; // Used in BitFramingReg. The number of valid bits in the last transmitted byte.
+ uint8_t *responseBuffer;
+ uint8_t responseLength;
+
+ // Description of buffer structure:
+ // Byte 0: SEL Indicates the Cascade Level: PICC_CMD_SEL_CL1, PICC_CMD_SEL_CL2 or PICC_CMD_SEL_CL3
+ // Byte 1: NVB Number of Valid Bits (in complete command, not just the UID): High nibble: complete bytes, Low nibble: Extra bits.
+ // Byte 2: UID-data or CT See explanation below. CT means Cascade Tag.
+ // Byte 3: UID-data
+ // Byte 4: UID-data
+ // Byte 5: UID-data
+ // Byte 6: BCC Block Check Character - XOR of bytes 2-5
+ // Byte 7: CRC_A
+ // Byte 8: CRC_A
+ // The BCC and CRC_A is only transmitted if we know all the UID bits of the current Cascade Level.
+ //
+ // Description of bytes 2-5: (Section 6.5.4 of the ISO/IEC 14443-3 draft: UID contents and cascade levels)
+ // UID size Cascade level Byte2 Byte3 Byte4 Byte5
+ // ======== ============= ===== ===== ===== =====
+ // 4 bytes 1 uid0 uid1 uid2 uid3
+ // 7 bytes 1 CT uid0 uid1 uid2
+ // 2 uid3 uid4 uid5 uid6
+ // 10 bytes 1 CT uid0 uid1 uid2
+ // 2 CT uid3 uid4 uid5
+ // 3 uid6 uid7 uid8 uid9
+
+ // Sanity checks
+ if (validBits > 80)
+ {
+ return STATUS_INVALID;
+ }
+
+ // Prepare MFRC522
+ PCD_ClearRegisterBitMask(CollReg, 0x80); // ValuesAfterColl=1 => Bits received after collision are cleared.
+
+ // Repeat Cascade Level loop until we have a complete UID.
+ uidComplete = false;
+ while ( ! uidComplete)
+ {
+ // Set the Cascade Level in the SEL byte, find out if we need to use the Cascade Tag in byte 2.
+ switch (cascadeLevel)
+ {
+ case 1:
+ buffer[0] = PICC_CMD_SEL_CL1;
+ uidIndex = 0;
+ useCascadeTag = validBits && uid->size > 4; // When we know that the UID has more than 4 bytes
+ break;
+
+ case 2:
+ buffer[0] = PICC_CMD_SEL_CL2;
+ uidIndex = 3;
+ useCascadeTag = validBits && uid->size > 7; // When we know that the UID has more than 7 bytes
+ break;
+
+ case 3:
+ buffer[0] = PICC_CMD_SEL_CL3;
+ uidIndex = 6;
+ useCascadeTag = false; // Never used in CL3.
+ break;
+
+ default:
+ return STATUS_INTERNAL_ERROR;
+ //break;
+ }
+
+ // How many UID bits are known in this Cascade Level?
+ if(validBits > (8 * uidIndex))
+ {
+ currentLevelKnownBits = validBits - (8 * uidIndex);
+ }
+ else
+ {
+ currentLevelKnownBits = 0;
+ }
+ // Copy the known bits from uid->uidByte[] to buffer[]
+ index = 2; // destination index in buffer[]
+ if (useCascadeTag)
+ {
+ buffer[index++] = PICC_CMD_CT;
+ }
+
+ uint8_t bytesToCopy = currentLevelKnownBits / 8 + (currentLevelKnownBits % 8 ? 1 : 0); // The number of bytes needed to represent the known bits for this level.
+ if (bytesToCopy)
+ {
+ uint8_t maxBytes = useCascadeTag ? 3 : 4; // Max 4 bytes in each Cascade Level. Only 3 left if we use the Cascade Tag
+ if (bytesToCopy > maxBytes)
+ {
+ bytesToCopy = maxBytes;
+ }
+
+ for (count = 0; count < bytesToCopy; count++)
+ {
+ buffer[index++] = uid->uidByte[uidIndex + count];
+ }
+ }
+ // Now that the data has been copied we need to include the 8 bits in CT in currentLevelKnownBits
+ if (useCascadeTag)
+ {
+ currentLevelKnownBits += 8;
+ }
+
+ // Repeat anti collision loop until we can transmit all UID bits + BCC and receive a SAK - max 32 iterations.
+ selectDone = false;
+ while ( ! selectDone)
+ {
+ // Find out how many bits and bytes to send and receive.
+ if (currentLevelKnownBits >= 32) { // All UID bits in this Cascade Level are known. This is a SELECT.
+ //Serial.print("SELECT: currentLevelKnownBits="); Serial.println(currentLevelKnownBits, DEC);
+ buffer[1] = 0x70; // NVB - Number of Valid Bits: Seven whole bytes
+ // Calulate BCC - Block Check Character
+ buffer[6] = buffer[2] ^ buffer[3] ^ buffer[4] ^ buffer[5];
+ // Calculate CRC_A
+ result = PCD_CalculateCRC(buffer, 7, &buffer[7]);
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+ txLastBits = 0; // 0 => All 8 bits are valid.
+ bufferUsed = 9;
+ // Store response in the last 3 bytes of buffer (BCC and CRC_A - not needed after tx)
+ responseBuffer = &buffer[6];
+ responseLength = 3;
+ }
+ else { // This is an ANTICOLLISION.
+ //Serial.print("ANTICOLLISION: currentLevelKnownBits="); Serial.println(currentLevelKnownBits, DEC);
+ txLastBits = currentLevelKnownBits % 8;
+ count = currentLevelKnownBits / 8; // Number of whole bytes in the UID part.
+ index = 2 + count; // Number of whole bytes: SEL + NVB + UIDs
+ buffer[1] = (index << 4) + txLastBits; // NVB - Number of Valid Bits
+ bufferUsed = index + (txLastBits ? 1 : 0);
+ // Store response in the unused part of buffer
+ responseBuffer = &buffer[index];
+ responseLength = sizeof(buffer) - index;
+ }
+
+ // Set bit adjustments
+ rxAlign = txLastBits; // Having a seperate variable is overkill. But it makes the next line easier to read.
+ PCD_WriteRegister(BitFramingReg, (rxAlign << 4) + txLastBits); // RxAlign = BitFramingReg[6..4]. TxLastBits = BitFramingReg[2..0]
+
+ // Transmit the buffer and receive the response.
+ result = PCD_TransceiveData(buffer, bufferUsed, responseBuffer, &responseLength, &txLastBits, rxAlign);
+ if (result == STATUS_COLLISION) { // More than one PICC in the field => collision.
+ result = PCD_ReadRegister(CollReg); // CollReg[7..0] bits are: ValuesAfterColl reserved CollPosNotValid CollPos[4:0]
+ if (result & 0x20) { // CollPosNotValid
+ return STATUS_COLLISION; // Without a valid collision position we cannot continue
+ }
+ uint8_t collisionPos = result & 0x1F; // Values 0-31, 0 means bit 32.
+ if (collisionPos == 0)
+ {
+ collisionPos = 32;
+ }
+ if (collisionPos <= currentLevelKnownBits) { // No progress - should not happen
+ return STATUS_INTERNAL_ERROR;
+ }
+ // Choose the PICC with the bit set.
+ currentLevelKnownBits = collisionPos;
+ count = (currentLevelKnownBits - 1) % 8; // The bit to modify
+ index = 1 + (currentLevelKnownBits / 8) + (count ? 1 : 0); // First byte is index 0.
+ buffer[index] |= (1 << count);
+ }
+ else if (result != STATUS_OK) {
+ return result;
+ }
+ else { // STATUS_OK
+ if (currentLevelKnownBits >= 32) { // This was a SELECT.
+ selectDone = true; // No more anticollision
+ // We continue below outside the while.
+ }
+ else { // This was an ANTICOLLISION.
+ // We now have all 32 bits of the UID in this Cascade Level
+ currentLevelKnownBits = 32;
+ // Run loop again to do the SELECT.
+ }
+ }
+ } // End of while ( ! selectDone)
+
+ // We do not check the CBB - it was constructed by us above.
+
+ // Copy the found UID bytes from buffer[] to uid->uidByte[]
+ index = (buffer[2] == PICC_CMD_CT) ? 3 : 2; // source index in buffer[]
+ bytesToCopy = (buffer[2] == PICC_CMD_CT) ? 3 : 4;
+ for (count = 0; count < bytesToCopy; count++)
+ {
+ uid->uidByte[uidIndex + count] = buffer[index++];
+ }
+
+ // Check response SAK (Select Acknowledge)
+ if (responseLength != 3 || txLastBits != 0) { // SAK must be exactly 24 bits (1 byte + CRC_A).
+ return STATUS_ERROR;
+ }
+ // Verify CRC_A - do our own calculation and store the control in buffer[2..3] - those bytes are not needed anymore.
+ result = PCD_CalculateCRC(responseBuffer, 1, &buffer[2]);
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+ if ((buffer[2] != responseBuffer[1]) || (buffer[3] != responseBuffer[2]))
+ {
+ return STATUS_CRC_WRONG;
+ }
+ if (responseBuffer[0] & 0x04) { // Cascade bit set - UID not complete yes
+ cascadeLevel++;
+ }
+ else
+ {
+ uidComplete = true;
+ uid->sak = responseBuffer[0];
+ }
+ } // End of while ( ! uidComplete)
+
+ // Set correct uid->size
+ uid->size = 3 * cascadeLevel + 1;
+
+ return STATUS_OK;
+} // End PICC_Select()
+
+/**
+ * Instructs a PICC in state ACTIVE(*) to go to state HALT.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PICC_HaltA()
+{
+ uint8_t result;
+ uint8_t buffer[4];
+
+ // Build command buffer
+ buffer[0] = PICC_CMD_HLTA;
+ buffer[1] = 0;
+ // Calculate CRC_A
+ result = PCD_CalculateCRC(buffer, 2, &buffer[2]);
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+
+ // Send the command.
+ // The standard says:
+ // If the PICC responds with any modulation during a period of 1 ms after the end of the frame containing the
+ // HLTA command, this response shall be interpreted as 'not acknowledge'.
+ // We interpret that this way: Only STATUS_TIMEOUT is an success.
+ result = PCD_TransceiveData(buffer, sizeof(buffer), NULL, 0);
+ if (result == STATUS_TIMEOUT)
+ {
+ return STATUS_OK;
+ }
+ if (result == STATUS_OK) { // That is ironically NOT ok in this case ;-)
+ return STATUS_ERROR;
+ }
+ return result;
+} // End PICC_HaltA()
+
+
+/////////////////////////////////////////////////////////////////////////////////////
+// Functions for communicating with MIFARE PICCs
+/////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Executes the MFRC522 MFAuthent command.
+ * This command manages MIFARE authentication to enable a secure communication to any MIFARE Mini, MIFARE 1K and MIFARE 4K card.
+ * The authentication is described in the MFRC522 datasheet section 10.3.1.9 and http://www.nxp.com/documents/data_sheet/MF1S503x.pdf section 10.1.
+ * For use with MIFARE Classic PICCs.
+ * The PICC must be selected - ie in state ACTIVE(*) - before calling this function.
+ * Remember to call PCD_StopCrypto1() after communicating with the authenticated PICC - otherwise no new communications can start.
+ *
+ * All keys are set to FFFFFFFFFFFFh at chip delivery.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise. Probably STATUS_TIMEOUT if you supply the wrong key.
+ */
+uint8_t MFRC522::PCD_Authenticate(uint8_t command, uint8_t blockAddr, MIFARE_Key *key, Uid *uid)
+{
+ uint8_t waitIRq = 0x10; // IdleIRq
+
+ // Build command buffer
+ uint8_t sendData[12];
+ sendData[0] = command;
+ sendData[1] = blockAddr;
+ for (uint8_t i = 0; i < MF_KEY_SIZE; i++) { // 6 key bytes
+ sendData[2+i] = key->keyByte[i];
+ }
+ for (uint8_t i = 0; i < 4; i++) { // The first 4 bytes of the UID
+ sendData[8+i] = uid->uidByte[i];
+ }
+
+ // Start the authentication.
+ return PCD_CommunicateWithPICC(PCD_MFAuthent, waitIRq, &sendData[0], sizeof(sendData));
+} // End PCD_Authenticate()
+
+/**
+ * Used to exit the PCD from its authenticated state.
+ * Remember to call this function after communicating with an authenticated PICC - otherwise no new communications can start.
+ */
+void MFRC522::PCD_StopCrypto1()
+{
+ // Clear MFCrypto1On bit
+ PCD_ClearRegisterBitMask(Status2Reg, 0x08); // Status2Reg[7..0] bits are: TempSensClear I2CForceHS reserved reserved MFCrypto1On ModemState[2:0]
+} // End PCD_StopCrypto1()
+
+/**
+ * Reads 16 bytes (+ 2 bytes CRC_A) from the active PICC.
+ *
+ * For MIFARE Classic the sector containing the block must be authenticated before calling this function.
+ *
+ * For MIFARE Ultralight only addresses 00h to 0Fh are decoded.
+ * The MF0ICU1 returns a NAK for higher addresses.
+ * The MF0ICU1 responds to the READ command by sending 16 bytes starting from the page address defined by the command argument.
+ * For example; if blockAddr is 03h then pages 03h, 04h, 05h, 06h are returned.
+ * A roll-back is implemented: If blockAddr is 0Eh, then the contents of pages 0Eh, 0Fh, 00h and 01h are returned.
+ *
+ * The buffer must be at least 18 bytes because a CRC_A is also returned.
+ * Checks the CRC_A before returning STATUS_OK.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_Read(uint8_t blockAddr, uint8_t *buffer, uint8_t *bufferSize)
+{
+ uint8_t result;
+
+ // Sanity check
+ if (buffer == NULL || *bufferSize < 18)
+ {
+ return STATUS_NO_ROOM;
+ }
+
+ // Build command buffer
+ buffer[0] = PICC_CMD_MF_READ;
+ buffer[1] = blockAddr;
+ // Calculate CRC_A
+ result = PCD_CalculateCRC(buffer, 2, &buffer[2]);
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+
+ // Transmit the buffer and receive the response, validate CRC_A.
+ return PCD_TransceiveData(buffer, 4, buffer, bufferSize, NULL, 0, true);
+} // End MIFARE_Read()
+
+/**
+ * Writes 16 bytes to the active PICC.
+ *
+ * For MIFARE Classic the sector containing the block must be authenticated before calling this function.
+ *
+ * For MIFARE Ultralight the opretaion is called "COMPATIBILITY WRITE".
+ * Even though 16 bytes are transferred to the Ultralight PICC, only the least significant 4 bytes (bytes 0 to 3)
+ * are written to the specified address. It is recommended to set the remaining bytes 04h to 0Fh to all logic 0.
+ * *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_Write(uint8_t blockAddr, uint8_t *buffer, uint8_t bufferSize)
+{
+ uint8_t result;
+
+ // Sanity check
+ if (buffer == NULL || bufferSize < 16)
+ {
+ return STATUS_INVALID;
+ }
+
+ // Mifare Classic protocol requires two communications to perform a write.
+ // Step 1: Tell the PICC we want to write to block blockAddr.
+ uint8_t cmdBuffer[2];
+ cmdBuffer[0] = PICC_CMD_MF_WRITE;
+ cmdBuffer[1] = blockAddr;
+ result = PCD_MIFARE_Transceive(cmdBuffer, 2); // Adds CRC_A and checks that the response is MF_ACK.
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+
+ // Step 2: Transfer the data
+ result = PCD_MIFARE_Transceive( buffer, bufferSize); // Adds CRC_A and checks that the response is MF_ACK.
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+
+ return STATUS_OK;
+} // End MIFARE_Write()
+
+/**
+ * Writes a 4 byte page to the active MIFARE Ultralight PICC.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_Ultralight_Write(uint8_t page, uint8_t *buffer, uint8_t bufferSize)
+{
+ uint8_t result;
+
+ // Sanity check
+ if (buffer == NULL || bufferSize < 4)
+ {
+ return STATUS_INVALID;
+ }
+
+ // Build commmand buffer
+ uint8_t cmdBuffer[6];
+ cmdBuffer[0] = PICC_CMD_UL_WRITE;
+ cmdBuffer[1] = page;
+ memcpy(&cmdBuffer[2], buffer, 4);
+
+ // Perform the write
+ result = PCD_MIFARE_Transceive(cmdBuffer, 6); // Adds CRC_A and checks that the response is MF_ACK.
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+ return STATUS_OK;
+} // End MIFARE_Ultralight_Write()
+
+/**
+ * MIFARE Decrement subtracts the delta from the value of the addressed block, and stores the result in a volatile memory.
+ * For MIFARE Classic only. The sector containing the block must be authenticated before calling this function.
+ * Only for blocks in "value block" mode, ie with access bits [C1 C2 C3] = [110] or [001].
+ * Use MIFARE_Transfer() to store the result in a block.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_Decrement(uint8_t blockAddr, uint32_t delta)
+{
+ return MIFARE_TwoStepHelper(PICC_CMD_MF_DECREMENT, blockAddr, delta);
+} // End MIFARE_Decrement()
+
+/**
+ * MIFARE Increment adds the delta to the value of the addressed block, and stores the result in a volatile memory.
+ * For MIFARE Classic only. The sector containing the block must be authenticated before calling this function.
+ * Only for blocks in "value block" mode, ie with access bits [C1 C2 C3] = [110] or [001].
+ * Use MIFARE_Transfer() to store the result in a block.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_Increment(uint8_t blockAddr, uint32_t delta)
+{
+ return MIFARE_TwoStepHelper(PICC_CMD_MF_INCREMENT, blockAddr, delta);
+} // End MIFARE_Increment()
+
+/**
+ * MIFARE Restore copies the value of the addressed block into a volatile memory.
+ * For MIFARE Classic only. The sector containing the block must be authenticated before calling this function.
+ * Only for blocks in "value block" mode, ie with access bits [C1 C2 C3] = [110] or [001].
+ * Use MIFARE_Transfer() to store the result in a block.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_Restore(uint8_t blockAddr)
+{
+ // The datasheet describes Restore as a two step operation, but does not explain what data to transfer in step 2.
+ // Doing only a single step does not work, so I chose to transfer 0L in step two.
+ return MIFARE_TwoStepHelper(PICC_CMD_MF_RESTORE, blockAddr, 0L);
+} // End MIFARE_Restore()
+
+/**
+ * Helper function for the two-step MIFARE Classic protocol operations Decrement, Increment and Restore.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_TwoStepHelper(uint8_t command, uint8_t blockAddr, uint32_t data)
+{
+ uint8_t result;
+ uint8_t cmdBuffer[2]; // We only need room for 2 bytes.
+
+ // Step 1: Tell the PICC the command and block address
+ cmdBuffer[0] = command;
+ cmdBuffer[1] = blockAddr;
+ result = PCD_MIFARE_Transceive( cmdBuffer, 2); // Adds CRC_A and checks that the response is MF_ACK.
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+
+ // Step 2: Transfer the data
+ result = PCD_MIFARE_Transceive((uint8_t *) &data, 4, true); // Adds CRC_A and accept timeout as success.
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+
+ return STATUS_OK;
+} // End MIFARE_TwoStepHelper()
+
+/**
+ * MIFARE Transfer writes the value stored in the volatile memory into one MIFARE Classic block.
+ * For MIFARE Classic only. The sector containing the block must be authenticated before calling this function.
+ * Only for blocks in "value block" mode, ie with access bits [C1 C2 C3] = [110] or [001].
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::MIFARE_Transfer(uint8_t blockAddr)
+{
+ uint8_t result;
+ uint8_t cmdBuffer[2]; // We only need room for 2 bytes.
+
+ // Tell the PICC we want to transfer the result into block blockAddr.
+ cmdBuffer[0] = PICC_CMD_MF_TRANSFER;
+ cmdBuffer[1] = blockAddr;
+ result = PCD_MIFARE_Transceive( cmdBuffer, 2); // Adds CRC_A and checks that the response is MF_ACK.
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+ return STATUS_OK;
+} // End MIFARE_Transfer()
+
+
+/////////////////////////////////////////////////////////////////////////////////////
+// Support functions
+/////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Wrapper for MIFARE protocol communication.
+ * Adds CRC_A, executes the Transceive command and checks that the response is MF_ACK or a timeout.
+ *
+ * @return STATUS_OK on success, STATUS_??? otherwise.
+ */
+uint8_t MFRC522::PCD_MIFARE_Transceive(uint8_t *sendData, uint8_t sendLen, bool acceptTimeout)
+{
+ uint8_t result;
+ uint8_t cmdBuffer[18]; // We need room for 16 bytes data and 2 bytes CRC_A.
+
+ // Sanity check
+ if (sendData == NULL || sendLen > 16)
+ {
+ return STATUS_INVALID;
+ }
+
+ // Copy sendData[] to cmdBuffer[] and add CRC_A
+ memcpy(cmdBuffer, sendData, sendLen);
+ result = PCD_CalculateCRC(cmdBuffer, sendLen, &cmdBuffer[sendLen]);
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+ sendLen += 2;
+
+ // Transceive the data, store the reply in cmdBuffer[]
+ uint8_t waitIRq = 0x30; // RxIRq and IdleIRq
+ uint8_t cmdBufferSize = sizeof(cmdBuffer);
+ uint8_t validBits = 0;
+ result = PCD_CommunicateWithPICC(PCD_Transceive, waitIRq, cmdBuffer, sendLen, cmdBuffer, &cmdBufferSize, &validBits);
+ if (acceptTimeout && result == STATUS_TIMEOUT)
+ {
+ return STATUS_OK;
+ }
+
+ if (result != STATUS_OK)
+ {
+ return result;
+ }
+
+ // The PICC must reply with a 4 bit ACK
+ if (cmdBufferSize != 1 || validBits != 4)
+ {
+ return STATUS_ERROR;
+ }
+
+ if (cmdBuffer[0] != MF_ACK)
+ {
+ return STATUS_MIFARE_NACK;
+ }
+
+ return STATUS_OK;
+} // End PCD_MIFARE_Transceive()
+
+
+/**
+ * Translates the SAK (Select Acknowledge) to a PICC type.
+ *
+ * @return PICC_Type
+ */
+uint8_t MFRC522::PICC_GetType(uint8_t sak)
+{
+ uint8_t retType = PICC_TYPE_UNKNOWN;
+
+ if (sak & 0x04) // UID not complete
+ {
+ retType = PICC_TYPE_NOT_COMPLETE;
+ }
+ else
+ {
+ switch (sak)
+ {
+ case 0x09: retType = PICC_TYPE_MIFARE_MINI; break;
+ case 0x08: retType = PICC_TYPE_MIFARE_1K; break;
+ case 0x18: retType = PICC_TYPE_MIFARE_4K; break;
+ case 0x00: retType = PICC_TYPE_MIFARE_UL; break;
+ case 0x10:
+ case 0x11: retType = PICC_TYPE_MIFARE_PLUS; break;
+ case 0x01: retType = PICC_TYPE_TNP3XXX; break;
+ default:
+ if (sak & 0x20)
+ {
+ retType = PICC_TYPE_ISO_14443_4;
+ }
+ else if (sak & 0x40)
+ {
+ retType = PICC_TYPE_ISO_18092;
+ }
+ break;
+ }
+ }
+
+ return (retType);
+} // End PICC_GetType()
+
+/**
+ * Returns a string pointer to the PICC type name.
+ *
+ */
+std::string MFRC522::PICC_GetTypeName(uint8_t piccType)
+{
+ if(piccType == PICC_TYPE_NOT_COMPLETE)
+ {
+ return ("SAK indicates UID is not complete.");
+ }
+
+ return(_TypeNamePICC[piccType]);
+} // End PICC_GetTypeName()
+
+/**
+ * Returns a string pointer to a status code name.
+ *
+ */
+std::string MFRC522::GetStatusCodeName(uint8_t code)
+{
+ return(_ErrorMessage[code]);
+} // End GetStatusCodeName()
+
+/**
+ * Calculates the bit pattern needed for the specified access bits. In the [C1 C2 C3] tupples C1 is MSB (=4) and C3 is LSB (=1).
+ */
+void MFRC522::MIFARE_SetAccessBits(uint8_t *accessBitBuffer, ///< Pointer to byte 6, 7 and 8 in the sector trailer. Bytes [0..2] will be set.
+ uint8_t g0, ///< Access bits [C1 C2 C3] for block 0 (for sectors 0-31) or blocks 0-4 (for sectors 32-39)
+ uint8_t g1, ///< Access bits C1 C2 C3] for block 1 (for sectors 0-31) or blocks 5-9 (for sectors 32-39)
+ uint8_t g2, ///< Access bits C1 C2 C3] for block 2 (for sectors 0-31) or blocks 10-14 (for sectors 32-39)
+ uint8_t g3) ///< Access bits C1 C2 C3] for the sector trailer, block 3 (for sectors 0-31) or block 15 (for sectors 32-39)
+{
+ uint8_t c1 = ((g3 & 4) << 1) | ((g2 & 4) << 0) | ((g1 & 4) >> 1) | ((g0 & 4) >> 2);
+ uint8_t c2 = ((g3 & 2) << 2) | ((g2 & 2) << 1) | ((g1 & 2) << 0) | ((g0 & 2) >> 1);
+ uint8_t c3 = ((g3 & 1) << 3) | ((g2 & 1) << 2) | ((g1 & 1) << 1) | ((g0 & 1) << 0);
+
+ accessBitBuffer[0] = (~c2 & 0xF) << 4 | (~c1 & 0xF);
+ accessBitBuffer[1] = c1 << 4 | (~c3 & 0xF);
+ accessBitBuffer[2] = c3 << 4 | c2;
+} // End MIFARE_SetAccessBits()
+
+/////////////////////////////////////////////////////////////////////////////////////
+// Convenience functions - does not add extra functionality
+/////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Returns true if a PICC responds to PICC_CMD_REQA.
+ * Only "new" cards in state IDLE are invited. Sleeping cards in state HALT are ignored.
+ *
+ * @return bool
+ */
+bool MFRC522::PICC_IsNewCardPresent()
+{
+ uint8_t bufferATQA[2];
+ uint8_t bufferSize = sizeof(bufferATQA);
+ uint8_t result = PICC_RequestA(bufferATQA, &bufferSize);
+ return (result == STATUS_OK || result == STATUS_COLLISION);
+} // End PICC_IsNewCardPresent()
+
+/**
+ * Simple wrapper around PICC_Select.
+ * Returns true if a UID could be read.
+ * Remember to call PICC_IsNewCardPresent(), PICC_RequestA() or PICC_WakeupA() first.
+ * The read UID is available in the class variable uid.
+ *
+ * @return bool
+ */
+bool MFRC522::PICC_ReadCardSerial()
+{
+ uint8_t result = PICC_Select(&uid);
+ return (result == STATUS_OK);
+} // End PICC_ReadCardSerial()