RFID

RFID is the acronym for Radio Frequency Identification. RFID is the technology that uses a radio frequency transmitter and a receiver to detect the presence of an object. The RFID technology is the most reliable and effective technology that can be used for the identification of uniqueness and presence of an object.

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The RFID transmitter is a fixed module which continues to emit radio signals through its antenna. The RFID receiver is also integrated with the same module to receive radio frequency.

The steps of RFID are :

  • The receiver sends Radio signals continuously.
  • The Signals received by the tag will activate the transponder of the tag and it will also generate a signal.
  • The Signal from the Tag is received by the receiver and the signal is response is checked in the database.
  • If a match is found, then a particular operation can be performed.

There are different ways to implement the RFID technology, based on the different frequency ranges used. They are:

  • Low Frequency : In the low-frequency system, the operational frequency ranges from 125 kHz to 134 kHz. The working distance(sending and receiving) is about 1 to 10 cm.
  • High Frequency : In the High-Frequency system, the operational frequency is about 13.56 MHz. The working distance is up to 1 meters
  • Ultra-High Frequency : In the Ultra High-Frequency system, the operational frequency is about 860-960 MHz. The working distance is up to 15 meters.

In the Low and High-frequency system, the internal frequency matching operation is done by inductive coupling. Inductive coupling is the process of inducing electromagnetic field into a coil due to another coil and vice versa.

In the case of the RFID, the inductive coupling does three things:

  • Induce enough current to activate the transponder in the RFID Tag.
  • Start the synchronization clock inside the Tag.
  • Carrier for the data which will be returned from the Tag.

In the Ultra High-Frequency system, the receiver or the reader will send signals continuously, this signal will be sensed by the Tag, and it will send a feedback signal, which is called the back-scattered signal.

This signal will be weaker compared to the reader's signal, but if the load on the Tag is matched, then the signal will have a significant magnitude. This is called Far Field Coupling. Through, this way also the RFID can be implemented.

There are two different types of RFID Tags which are available in the market:

  • Active RFID Tag : Active RFID Tag is the one that has its own power supply inside it, and only the transponder inside it has to be activated with the help of the reader's signal. This is used only in areas where the sensing has to be done very fast, and there are no problems if the Tag size is larger.
  • Passive RFID Tag : Passive RFID Tag is the one that does not have its own power supply. It can start its operation only when it is brought closer to the RFID reader(the transmitter & receiver). Passive RFID tags are handy and compact and are used in different areas.

Applications of RFID

There are infinite applications of RFID Technology. Some of the most appreciable applications are as follows:

  • Logistics : RFID has a very huge impact on producing real-time data on delivery of items or products which are dispatched from a logistics. Also in the case of supply chain and manufacturing, in different phases, the implementation of RFID to detect the completed phases, can be very useful in saving time.
  • Games and sports : There are many games and outdoor sports which are based on timings. For, example, in the case of a Racing game, the RFID Tag is integrated with the Sportswear that the athletes wear. Now, in this case, the RFID will automatically detect the distance covered and also whether the completion ribbon is reached or not. This RFID can be applied in such cases to give unbiased results.
  • Attendance Management System : There are companies, warehouses or repositories where there are hundreds of employees and workers working. Therefore, the automatic attendance system can help to decrease the overhead of keeping records of attendance, and all the individual employees carry out the work for himself.
  • Authorized Access : There can be different areas where authorized access is required, in such cases the RFID Tags can be provided to only those individuals who are authorized. The applicable areas may be parking lots, doors, lockers, etc.
  • Kiosk : Kiosks are nowadays the most reliable form of business. Here, the customers can automatically check and uncheck items and decide whether and which items to buy in the absence of the shop owner or the Vendor. In such a case, the RFID Tags to be given to the verified customers who can directly swipe or enter the card in the Kiosk and make a purchase.
  • Digital Library Systems : In the Digital Library Systems, the books contain an RFID Tag (in the form of a small chip inside it), when the authorized card is produced in the Kiosk, the student gains an access to the interface which asks for the credentials and this can issue the book without any paperwork.
  • Real-Time Location System : There are areas where the movements of the workers or employees should be recorded. In such cases also the RFID can play a very important role in tracking the location of the workers or of the robot.

RFID with Arduino (RC522 Module)

There are different RFID modules which are the integrated component of RFID transmitter and receiver. And also, there are different types of Tags. Tags are used for unique identification. The tags can be in the form of a Card(ATM card sized) or in the form of a key-ring or any custom sized.

RFID - RC522 Module

This module is the most compact, advanced and most reliable to use. This module can be easily integrated with any versions of the Arduino Board. As this is the most used RFID module, we shall confine our study and project with the RC522 RFID module.

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Features & Specifications :
  • Highly integrated.
  • Operating Frequency: 13.56 MHz
  • Operating Voltage(Supply): 3.3 volts.
  • Current: 13 to 16 mA.
  • Reading Range: 3 cm approx.
  • Data transfer rate: 10 Mb/sec (maximum)
  • Physical Dimension: 60 mm * 39 mm.
  • Connecting Interface: SPI.

Components Required:

  • Arduino Uno Board.
  • RC522 RFID Module.
  • Breadboard.
  • Jumper Wires.
  • 16 * 2 LCD Display.

Connecting the LCD Module to the Arduino

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Connecting the RC522 Module to the Arduino

Add the steps and image here..

Edit the following code into the Arduino Editor

#include <SPI.h>
#include <LiquidCrystal.h>
#include<Servo.h>
Servo myservo;
#define uchar unsigned char
# define uint unsigned int
//data array maxium length
# define MAX_LEN 16
const int chipSelectPin = 10;
const int NRSTPD = 9;
LiquidCrystal lcd(2, 3, 4, 5, 8, 7);
int buzzerpin = 8;
int mypin = 6;
//MF522 command bits
#define PCD_IDLE 0x00 //NO action; cancel current commands
# define PCD_AUTHENT 0x0E //verify password key
# define PCD_RECEIVE 0x08 //receive data
# define PCD_TRANSMIT 0x04 //send data
# define PCD_TRANSCEIVE 0x0C //send and receive data
# define PCD_RESETPHASE 0x0F //reset
# define PCD_CALCCRC 0x03 //CRC check and caculation

//Mifare_One card command bits
# define PICC_REQIDL 0x26 //Search the cards that not into sleep mode in the antenna area 
# define PICC_REQALL 0x52 //Search all the cards in the antenna area
# define PICC_ANTICOLL 0x93 //prevent conflict
# define PICC_SElECTTAG 0x93 //select card
# define PICC_AUTHENT1A 0x60 //verify A password key
# define PICC_AUTHENT1B 0x61 //verify B password key
# define PICC_READ 0x30 //read 
# define PICC_WRITE 0xA0 //write
# define PICC_DECREMENT 0xC0 //deduct value
# define PICC_INCREMENT 0xC1 //charge up value
# define PICC_RESTORE 0xC2 //Restore data into buffer
# define PICC_TRANSFER 0xB0 //Save data into buffer
# define PICC_HALT 0x50 //sleep mode

//THe mistake code that return when communicate with MF522
# define MI_OK 0# define MI_NOTAGERR 1# define MI_ERR 2

//------------------MFRC522 register ---------------
//Page 0:Command and Status
# define Reserved00 0x00
# define CommandReg 0x01
# define CommIEnReg 0x02
# define DivlEnReg 0x03
# define CommIrqReg 0x04
# define DivIrqReg 0x05
# define ErrorReg 0x06
# define Status1Reg 0x07
# define Status2Reg 0x08
# define FIFODataReg 0x09
# define FIFOLevelReg 0x0A
# define WaterLevelReg 0x0B
# define ControlReg 0x0C
# define BitFramingReg 0x0D
# define CollReg 0x0E
# define Reserved01 0x0F
//Page 1:Command 
# define Reserved10 0x10
# define ModeReg 0x11
# define TxModeReg 0x12
# define RxModeReg 0x13
# define TxControlReg 0x14
# define TxAutoReg 0x15
# define TxSelReg 0x16
# define RxSelReg 0x17
# define RxThresholdReg 0x18
# define DemodReg 0x19
# define Reserved11 0x1A
# define Reserved12 0x1B
# define MifareReg 0x1C
# define Reserved13 0x1D
# define Reserved14 0x1E
# define SerialSpeedReg 0x1F
//Page 2:CFG 
# define Reserved20 0x20
# define CRCResultRegM 0x21
# define CRCResultRegL 0x22
# define Reserved21 0x23
# define ModWidthReg 0x24
# define Reserved22 0x25
# define RFCfgReg 0x26
# define GsNReg 0x27
# define CWGsPReg 0x28
# define ModGsPReg 0x29
# define TModeReg 0x2A
# define TPrescalerReg 0x2B
# define TReloadRegH 0x2C
# define TReloadRegL 0x2D
# define TCounterValueRegH 0x2E
# define TCounterValueRegL 0x2F
//Page 3:TestRegister 
# define Reserved30 0x30
# define TestSel1Reg 0x31
# define TestSel2Reg 0x32
# define TestPinEnReg 0x33
# define TestPinValueReg 0x34
# define TestBusReg 0x35
# define AutoTestReg 0x36
# define VersionReg 0x37
# define AnalogTestReg 0x38
# define TestDAC1Reg 0x39
# define TestDAC2Reg 0x3A
# define TestADCReg 0x3B
# define Reserved31 0x3C
# define Reserved32 0x3D
# define Reserved33 0x3E
# define Reserved34 0x3F
//-----------------------------------------------

//4 bytes Serial number of card, the 5 bytes is verfiy bytes
uchar serNum[5];

void setup() {

    myservo.attach(mypin);
    SPI.begin();
    lcd.begin(16, 2);
    lcd.clear();
    pinMode(buzzerpin, OUTPUT);
    pinMode(chipSelectPin, OUTPUT);
    digitalWrite(chipSelectPin, LOW); // Activate the RFID reader
    pinMode(NRSTPD, OUTPUT); // Set digital pin 5 , Not Reset and Power-down

    MFRC522_Init();
}

void loop() {

    lcd.setCursor(0, 0); // set the cursor to column 0, line 0
    lcd.print("Swipe Card"); // Print a message of "Temp: "to the LCD.
    uchar status;
    uchar str[MAX_LEN];

    //  lcd.setCursor(0, 0); // set the cursor to column 0, line 0
    //  lcd.print("Swipe Card");// Print a message of "Temp: "to the LCD.

    // Search card, return card types
    status = MFRC522_Request(PICC_REQIDL, str);
    if (status != MI_OK) {
        return;
    }

    // Show card type
    ShowCardType(str);

    //Prevent conflict, return the 4 bytes Serial number of the card
    status = MFRC522_Anticoll(str);

    // str[0..3]: serial number of the card
    // str[4]: XOR checksum of the SN.
    if (status == MI_OK) {
        Serial.print("The card's number is: ");
        memcpy(serNum, str, 5);
        ShowCardID(serNum);

        // Check people associated with card ID
        uchar * id = serNum;
        lcd.setCursor(8, 0);
        int lcdid = 4;
        for (int i = 0; i < lcdid; i++) {
            //  lcd.print(0x0F & (id[i]>>4), HEX);
            // lcd.print(0x0F & id[i],HEX);

        }

        if (id[0] == 0xE9 && id[1] == 0x76 && id[2] == 0xFE && id[3] == 0x15) {
            Serial.println("Welcome Chercher.tech");
            lcd.setCursor(0, 1); // set the cursor to column 0, line 0
            // lcd.print("Swipe Card");// Print a message of "Temp: "to the LCD.
            myservo.write(360);
            lcd.print("door open");

        } else if (id[0] == 0x03 && id[1] == 0xA2 && id[2] == 0x67 && id[3] == 0x00) {
            Serial.println("Hello Tom!      ");
            lcd.setCursor(0, 1); // set the cursor to column 0, line 0
            lcd.print("   Hello Tom!   "); // Print a message of "Temp: "to the LCD.
        } else {
            Serial.println("Hello unkown guy");
            lcd.setCursor(0, 1); // set the cursor to column 0, line 0
            lcd.print("Door Locked"); // Print a message of "Temp: "to the LCD.
            myservo.write(0);
        }

    }

    MFRC522_Halt(); //command the card into sleep mode 
    for (int n = 1; n < 100; n++) {
        digitalWrite(buzzerpin, HIGH);
        delayMicroseconds(500);
        digitalWrite(buzzerpin, LOW);
    }
    delay(2000);
}

void ShowCardID(uchar * id) {
    int IDlen = 4;
    for (int i = 0; i < IDlen; i++) {
        Serial.print(0x0F & (id[i] >> 4), HEX);
        Serial.print(0x0F & id[i], HEX);
    }
    Serial.println("");
}

void ShowCardType(uchar * type) {
    Serial.print("Card type: ");
    if (type[0] == 0x04 && type[1] == 0x00)
        Serial.println("MFOne-S50");
    else if (type[0] == 0x02 && type[1] == 0x00)
        Serial.println("MFOne-S70");
    else if (type[0] == 0x44 && type[1] == 0x00)
        Serial.println("MF-UltraLight");
    else if (type[0] == 0x08 && type[1] == 0x00)
        Serial.println("MF-Pro");
    else if (type[0] == 0x44 && type[1] == 0x03)
        Serial.println("MF Desire");
    else
        Serial.println("Unknown");
}

/*
 * Function:Write_MFRC5200
 * Description:write a byte data into one register of MR RC522
 * Input parameter:addr--register address;val--the value that need to write in
 * Return:Null
 */
void Write_MFRC522(uchar addr, uchar val) {
    digitalWrite(chipSelectPin, LOW);

    //address format:0XXXXXX0
    SPI.transfer((addr << 1) & 0x7E);
    SPI.transfer(val);

    digitalWrite(chipSelectPin, HIGH);
}

/*
 * Function:Read_MFRC522
 * Description:read a byte data into one register of MR RC522
 * Input parameter:addr--register address
 * Return:return the read value
 */
uchar Read_MFRC522(uchar addr) {
    uchar val;

    digitalWrite(chipSelectPin, LOW);

    //address format:1XXXXXX0
    SPI.transfer(((addr << 1) & 0x7E) | 0x80);
    val = SPI.transfer(0x00);

    digitalWrite(chipSelectPin, HIGH);

    return val;
}

/*
 * Function:SetBitMask
 * Description:set RC522 register bit
 * Input parameter:reg--register address;mask--value
 * Return:null
 */
void SetBitMask(uchar reg, uchar mask) {
    uchar tmp;
    tmp = Read_MFRC522(reg);
    Write_MFRC522(reg, tmp | mask); // set bit mask
}

/*
 * Function:ClearBitMask
 * Description:clear RC522 register bit
 * Input parameter:reg--register address;mask--value
 * Return:null
 */
void ClearBitMask(uchar reg, uchar mask) {
    uchar tmp;
    tmp = Read_MFRC522(reg);
    Write_MFRC522(reg, tmp & (~mask)); // clear bit mask
}

/*
 * Function:AntennaOn
 * Description:Turn on antenna, every time turn on or shut down antenna need at least 1ms delay
 * Input parameter:null
 * Return:null
 */
void AntennaOn(void) {
    uchar temp;

    temp = Read_MFRC522(TxControlReg);
    if (!(temp & 0x03)) {
        SetBitMask(TxControlReg, 0x03);
    }
}

/*
 * Function:AntennaOff
 * Description:Turn off antenna, every time turn on or shut down antenna need at least 1ms delay
 * Input parameter:null
 * Return:null
 */
void AntennaOff(void) {
    ClearBitMask(TxControlReg, 0x03);
}

/*
 * Function:ResetMFRC522
 * Description: reset RC522
 * Input parameter:null
 * Return:null
 */
void MFRC522_Reset(void) {
    Write_MFRC522(CommandReg, PCD_RESETPHASE);
}

/*
 * Function:InitMFRC522
 * Description:initilize RC522
 * Input parameter:null
 * Return:null
 */
void MFRC522_Init(void) {
    digitalWrite(NRSTPD, HIGH);

    MFRC522_Reset();

    //Timer: TPrescaler*TreloadVal/6.78MHz = 24ms
    Write_MFRC522(TModeReg, 0x8D); //Tauto=1; f(Timer) = 6.78MHz/TPreScaler
    Write_MFRC522(TPrescalerReg, 0x3E); //TModeReg[3..0] + TPrescalerReg
    Write_MFRC522(TReloadRegL, 30);
    Write_MFRC522(TReloadRegH, 0);

    Write_MFRC522(TxAutoReg, 0x40); //100%ASK
    Write_MFRC522(ModeReg, 0x3D); //CRC initilizate value 0x6363 ???

    //ClearBitMask(Status2Reg, 0x08); //MFCrypto1On=0
    //Write_MFRC522(RxSelReg, 0x86); //RxWait = RxSelReg[5..0]
    //Write_MFRC522(RFCfgReg, 0x7F); //RxGain = 48dB

    AntennaOn(); //turn on antenna
}

/*
 * Function:MFRC522_Request
 * Description:Searching card, read card type
 * Input parameter:reqMode--search methods,
 * TagType--return card types
 * 0x4400 = Mifare_UltraLight
 * 0x0400 = Mifare_One(S50)
 * 0x0200 = Mifare_One(S70)
 * 0x0800 = Mifare_Pro(X)
 * 0x4403 = Mifare_DESFire
 * return:return MI_OK if successed
 */
uchar MFRC522_Request(uchar reqMode, uchar * TagType) {
    uchar status;
    uint backBits; //the data bits that received

    Write_MFRC522(BitFramingReg, 0x07); //TxLastBists = BitFramingReg[2..0] ???

    TagType[0] = reqMode;
    status = MFRC522_ToCard(PCD_TRANSCEIVE, TagType, 1, TagType, & backBits);

    if ((status != MI_OK) || (backBits != 0x10)) {
        status = MI_ERR;
    }

    return status;
}

/*
 * Function:MFRC522_ToCard
 * Description:communicate between RC522 and ISO14443
 * Input parameter:command--MF522 command bits
 * sendData--send data to card via rc522
 * sendLen--send data length 
 * backData--the return data from card
 * backLen--the length of return data
 * return:return MI_OK if successed
 */
uchar MFRC522_ToCard(uchar command, uchar * sendData, uchar sendLen, uchar * backData, uint * backLen) {
    uchar status = MI_ERR;
    uchar irqEn = 0x00;
    uchar waitIRq = 0x00;
    uchar lastBits;
    uchar n;
    uint i;

    switch (command) {
    case PCD_AUTHENT: //verify card password
        {
            irqEn = 0x12;
            waitIRq = 0x10;
            break;
        }
    case PCD_TRANSCEIVE: //send data in the FIFO
        {
            irqEn = 0x77;
            waitIRq = 0x30;
            break;
        }
    default:
        break;
    }

    Write_MFRC522(CommIEnReg, irqEn | 0x80); //Allow interruption
    ClearBitMask(CommIrqReg, 0x80); //Clear all the interrupt bits
    SetBitMask(FIFOLevelReg, 0x80); //FlushBuffer=1, FIFO initilizate

    Write_MFRC522(CommandReg, PCD_IDLE); //NO action;cancel current command ???

    //write data into FIFO
    for (i = 0; i < sendLen; i++) {
        Write_MFRC522(FIFODataReg, sendData[i]);
    }

    //procceed it
    Write_MFRC522(CommandReg, command);
    if (command == PCD_TRANSCEIVE) {
        SetBitMask(BitFramingReg, 0x80); //StartSend=1,transmission of data starts 
    }

    //waite receive data is finished
    i = 2000; //i should adjust according the clock, the maxium the waiting time should be 25 ms???
    do {
        //CommIrqReg[7..0]
        //Set1 TxIRq RxIRq IdleIRq HiAlerIRq LoAlertIRq ErrIRq TimerIRq
        n = Read_MFRC522(CommIrqReg);
        i--;
    }
    while ((i != 0) && !(n & 0x01) && !(n & waitIRq));

    ClearBitMask(BitFramingReg, 0x80); //StartSend=0

    if (i != 0) {
        if (!(Read_MFRC522(ErrorReg) & 0x1B)) //BufferOvfl Collerr CRCErr ProtecolErr
        {
            status = MI_OK;
            if (n & irqEn & 0x01) {
                status = MI_NOTAGERR; //?? 
            }

            if (command == PCD_TRANSCEIVE) {
                n = Read_MFRC522(FIFOLevelReg);
                lastBits = Read_MFRC522(ControlReg) & 0x07;
                if (lastBits) {
                    * backLen = (n - 1) * 8 + lastBits;
                } else {
                    * backLen = n * 8;
                }

                if (n == 0) {
                    n = 1;
                }
                if (n > MAX_LEN) {
                    n = MAX_LEN;
                }

                //read the data from FIFO
                for (i = 0; i < n; i++) {
                    backData[i] = Read_MFRC522(FIFODataReg);
                }
            }
        } else {
            status = MI_ERR;
        }

    }

    //SetBitMask(ControlReg,0x80); //timer stops
    //Write_MFRC522(CommandReg, PCD_IDLE); 

    return status;
}

/*
 * Function:MFRC522_Anticoll
 * Description:Prevent conflict, read the card serial number 
 * Input parameter:serNum--return the 4 bytes card serial number, the 5th byte is recheck byte
 * return:return MI_OK if successed
 */
uchar MFRC522_Anticoll(uchar * serNum) {
    uchar status;
    uchar i;
    uchar serNumCheck = 0;
    uint unLen;

    //ClearBitMask(Status2Reg, 0x08); //strSensclear
    //ClearBitMask(CollReg,0x80); //ValuesAfterColl
    Write_MFRC522(BitFramingReg, 0x00); //TxLastBists = BitFramingReg[2..0]

    serNum[0] = PICC_ANTICOLL;
    serNum[1] = 0x20;
    status = MFRC522_ToCard(PCD_TRANSCEIVE, serNum, 2, serNum, & unLen);

    if (status == MI_OK) {
        //Verify card serial number
        for (i = 0; i < 4; i++) {
            serNumCheck ^= serNum[i];
        }
        if (serNumCheck != serNum[i]) {
            status = MI_ERR;
        }
    }

    //SetBitMask(CollReg, 0x80); //ValuesAfterColl=1

    return status;
}

/*
 * Function:CalulateCRC
 * Description:Use MF522 to caculate CRC
 * Input parameter:pIndata--the CRC data need to be read,len--data length,pOutData-- the caculated result of CRC
 * return:Null
 */
void CalulateCRC(uchar * pIndata, uchar len, uchar * pOutData) {
    uchar i, n;

    ClearBitMask(DivIrqReg, 0x04); //CRCIrq = 0
    SetBitMask(FIFOLevelReg, 0x80); //Clear FIFO pointer
    //Write_MFRC522(CommandReg, PCD_IDLE);

    //Write data into FIFO 
    for (i = 0; i < len; i++) {
        Write_MFRC522(FIFODataReg, *(pIndata + i));
    }
    Write_MFRC522(CommandReg, PCD_CALCCRC);

    //waite CRC caculation to finish
    i = 0xFF;
    do {
        n = Read_MFRC522(DivIrqReg);
        i--;
    }
    while ((i != 0) && !(n & 0x04)); //CRCIrq = 1

    //read CRC caculation result
    pOutData[0] = Read_MFRC522(CRCResultRegL);
    pOutData[1] = Read_MFRC522(CRCResultRegM);
}

/*
 * Function:MFRC522_Write
 * Description:write block data
 * Input parameters:blockAddr--block address;writeData--Write 16 bytes data into block
 * return:return MI_OK if successed
 */
uchar MFRC522_Write(uchar blockAddr, uchar * writeData) {
    uchar status;
    uint recvBits;
    uchar i;
    uchar buff[18];

    buff[0] = PICC_WRITE;
    buff[1] = blockAddr;
    CalulateCRC(buff, 2, & buff[2]);
    status = MFRC522_ToCard(PCD_TRANSCEIVE, buff, 4, buff, & recvBits);

    if ((status != MI_OK) || (recvBits != 4) || ((buff[0] & 0x0F) != 0x0A)) {
        status = MI_ERR;
    }

    if (status == MI_OK) {
        for (i = 0; i < 16; i++) //Write 16 bytes data into FIFO
        {
            buff[i] = * (writeData + i);
        }
        CalulateCRC(buff, 16, & buff[16]);
        status = MFRC522_ToCard(PCD_TRANSCEIVE, buff, 18, buff, & recvBits);

        if ((status != MI_OK) || (recvBits != 4) || ((buff[0] & 0x0F) != 0x0A)) {
            status = MI_ERR;
        }
    }

    return status;
}

/*
 * Function:MFRC522_Halt
 * Description:Command the cards into sleep mode
 * Input parameters:null
 * return:null
 */
void MFRC522_Halt(void) {
    uchar status;
    uint unLen;
    uchar buff[4];

    buff[0] = PICC_HALT;
    buff[1] = 0;
    CalulateCRC(buff, 2, & buff[2]);

    status = MFRC522_ToCard(PCD_TRANSCEIVE, buff, 4, buff, & unLen);
}
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