RFID.h

#include <MFRC522.h>
#define SS_PIN    21
#define RST_PIN   22

String Card_code;
int scan_to_post = 0;

MFRC522 RFID(SS_PIN, RST_PIN);   // 創建新的RFID實例
MFRC522::MIFARE_Key key;
void RFID_init()
{
  SPI.begin();
  RFID.PCD_Init();

  for (byte i = 0; i < 6; i++)
  {
    key.keyByte[i] = 0xFF;
  }

}
void dump_byte_array(byte *buffer, byte bufferSize)
{
  Card_code = "";
  String code_temp[4];
  for (byte i = 0; i < bufferSize; i++)
  {
    code_temp[i] = buffer[i];
    Card_code += code_temp[i];
  }
  scan_to_post = 1;
  Serial.println(Card_code);
  Serial.println();

}

void read_RFID()
{
  if ( ! RFID.PICC_ReadCardSerial())
  {
    delay(50);
    return;
  }
  Serial.println("RFID Tag Detected...");
  Serial.print(F("Card UID:"));
  dump_byte_array(RFID.uid.uidByte, RFID.uid.size);
}

int money_dec(byte *buffer ,byte bufferSize)
{
  String tmp[3];
  for (byte i = 0; i < bufferSize; i++)
  {
    tmp[i] = String(buffer[i], HEX);
  }
  tmp[3] = tmp[0] + tmp[1];
  long money_dec = strtol(tmp[3].c_str(), NULL, 16);
  return money_dec;
}

int dump_byte_array_RW(byte *buffer, byte bufferSize)
{
    for (byte i = 0; i < bufferSize; i++)
    {
        Serial.print(buffer[i] < 0x10 ? " 0" : " ");
        Serial.print(buffer[i], HEX);
    }
    int money = money_dec(buffer,bufferSize);
    return money;
}


int read_RFID_sector()
{
    byte sector         = 1;
    byte blockAddr      = 4;

    byte buffer[18];
    byte size = sizeof(buffer);
    RFID.PICC_DumpMifareClassicSectorToSerial(&(RFID.uid), &key, sector);
    Serial.println();
    //read
    RFID.MIFARE_Read(blockAddr, buffer, &size);
    Serial.print(F("Data in block "));
    Serial.print(blockAddr);
    Serial.println(F(":"));
    int money = dump_byte_array_RW(buffer, 2);
    Serial.println();

    RFID.PICC_HaltA();
    // Stop encryption on PCD
    RFID.PCD_StopCrypto1();
    return money;
}

int write_rfid(int money)
{
  // Show some details of the PICC (that is: the tag/card)
    Serial.print(F("Card UID:"));
    dump_byte_array_RW(RFID.uid.uidByte, RFID.uid.size);
    Serial.println();
    Serial.print(F("PICC type: "));
    MFRC522::PICC_Type piccType = RFID.PICC_GetType(RFID.uid.sak);
    Serial.println(RFID.PICC_GetTypeName(piccType));

    // Check for compatibility
    if (    piccType != MFRC522::PICC_TYPE_MIFARE_MINI
        &&  piccType != MFRC522::PICC_TYPE_MIFARE_1K
        &&  piccType != MFRC522::PICC_TYPE_MIFARE_4K)
    {
        Serial.println(F("This sample only works with MIFARE Classic cards."));
        return '0';
    }


    byte sector         = 1;
    byte blockAddr      = 4;
    String tmp[3];
    tmp[2] =  String(money, HEX);
    tmp[0] = tmp[2].substring(0,2);
    tmp[1] = tmp[2].substring(2);

    byte tmp1 = strtol(tmp[0].c_str(), NULL, 16);
    byte tmp2 = strtol(tmp[1].c_str(), NULL, 16);
    byte dataBlock[]    =
    {
        tmp1, tmp2, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00
    };

    MFRC522::StatusCode status;
    byte buffer[18];
    byte size = sizeof(buffer);

    Serial.println(dataBlock[0]);
    Serial.println(dataBlock[1]);
    byte trailerBlock   = 7;

    // Authenticate using key A
    Serial.println(F("Authenticating using key A..."));
    status = (MFRC522::StatusCode) RFID.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, trailerBlock, &key, &(RFID.uid));
    if (status != MFRC522::STATUS_OK)
    {
        Serial.print(F("PCD_Authenticate() failed: "));
        Serial.println(RFID.GetStatusCodeName(status));
        return '1';
    }

    // Show the whole sector as it currently is
    Serial.println(F("Current data in sector:"));
    RFID.PICC_DumpMifareClassicSectorToSerial(&(RFID.uid), &key, sector);
    Serial.println();

    // Read data from the block
    Serial.print(F("Reading data from block ")); Serial.print(blockAddr);
    Serial.println(F(" ..."));
    status = (MFRC522::StatusCode) RFID.MIFARE_Read(blockAddr, buffer, &size);
    if (status != MFRC522::STATUS_OK)
    {
        Serial.print(F("MIFARE_Read() failed: "));
        Serial.println(RFID.GetStatusCodeName(status));
    }
    Serial.print(F("Data in block ")); Serial.print(blockAddr); Serial.println(F(":"));
    dump_byte_array_RW(buffer, 16); Serial.println();
    Serial.println();

    // Authenticate using key B
    Serial.println(F("Authenticating again using key B..."));
    status = (MFRC522::StatusCode) RFID.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_B, trailerBlock, &key, &(RFID.uid));
    if (status != MFRC522::STATUS_OK) {
        Serial.print(F("PCD_Authenticate() failed: "));
        Serial.println(RFID.GetStatusCodeName(status));
        return '2';
    }

    // Write data to the block
    Serial.print(F("Writing data into block ")); Serial.print(blockAddr);
    Serial.println(F(" ..."));
    dump_byte_array_RW(dataBlock, 16); Serial.println();
    status = (MFRC522::StatusCode) RFID.MIFARE_Write(blockAddr, dataBlock, 16);
    if (status != MFRC522::STATUS_OK)
    {
        Serial.print(F("MIFARE_Write() failed: "));
        Serial.println(RFID.GetStatusCodeName(status));
    }
    Serial.println();

    // Read data from the block (again, should now be what we have written)
    Serial.print(F("Reading data from block ")); Serial.print(blockAddr);
    Serial.println(F(" ..."));
    status = (MFRC522::StatusCode) RFID.MIFARE_Read(blockAddr, buffer, &size);
    if (status != MFRC522::STATUS_OK)
    {
        Serial.print(F("MIFARE_Read() failed: "));
        Serial.println(RFID.GetStatusCodeName(status));
    }
    Serial.print(F("Data in block ")); Serial.print(blockAddr); Serial.println(F(":"));
    dump_byte_array_RW(buffer, 16); Serial.println();

    // Check that data in block is what we have written
    // by counting the number of bytes that are equal
    Serial.println(F("Checking result..."));
    byte count = 0;
    for (byte i = 0; i < 16; i++)
    {
        // Compare buffer (= what we've read) with dataBlock (= what we've written)
        if (buffer[i] == dataBlock[i])
            count++;
    }
    Serial.print(F("Number of bytes that match = ")); Serial.println(count);
    if (count == 16)
    {
        Serial.println(F("Success :-)"));
    }
    else
    {
        Serial.println(F("Failure, no match :-("));
        Serial.println(F("  perhaps the write didn't work properly..."));
    }
    Serial.println();

    // Dump the sector data
    Serial.println(F("Current data in sector:"));
    RFID.PICC_DumpMifareClassicSectorToSerial(&(RFID.uid), &key, sector);
    Serial.println();

    // Halt PICC
    RFID.PICC_HaltA();
    // Stop encryption on PCD
    RFID.PCD_StopCrypto1();
}

void Detect_RFID()
{
  if ( ! RFID.PICC_IsNewCardPresent())
  {
    return;
  }
  read_RFID();
  int money = read_RFID_sector();
  money -= 60;
  delay(1000);
  write_rfid(money);
}