linux下RFID卡（门禁卡，Mifare卡）的编程

    我使用的是串口读卡器，RFID卡是philips的Mifare-M1卡。操作读卡器，就是操作串口设备。串口设备的基础只是，请参考 https://www.ibm.com/developerworks/cn/linux/l-serials/ ，此文讲得很详细。
    在嵌入式平台下，串口设置需要做得更全一些，以避免一些特殊字符问题。本文描述了一种用select进行非阻塞方式读取的方法，方便了应用程序进行整合。
1，打开串口

int open_comm (const char* device) {
    if (device == NULL) return -1;
    int fd = open (device, O_RDWR|O_NOCTTY|O_NDELAY);
    return fd;
}

2，设置串口

static int speed_arr[] = {B115200, B38400, B19200, B9600, B4800, B2400, B1200, B300,
                          B38400, B19200, B9600, B4800, B2400, B1200, B300, };
static int name_arr[] = { 115200, 38400,  19200,  9600,  4800,  2400,  1200,  300,
                          38400,  19200,  9600, 4800, 2400, 1200,  300, };

int set_options (int fd, int speed, int databits, int stopbits, int parity) {
    struct termios options;
    int status = 0;
    if ((status = tcgetattr (fd, &options)) != 0) {
        ERROR ("fail: status=%d, %s", status, strerror (errno));
        return -1;
    }

    int bSpeed = -1;
    for (int i = 0; i < sizeof(speed_arr) / sizeof(int); i++) {
        if (speed == name_arr[i]) {
            bSpeed = speed_arr[i];
            break;
        }
    }
    if (bSpeed == -1) {
        ERROR ("wrong speed=%d", speed);
        return -1;
    }
    cfsetispeed (&options, bSpeed);
    cfsetospeed (&options, bSpeed);

    /*允许接收并且设置为本地模式*/
    options.c_cflag |= (CLOCAL|CREAD);

    /*设置数据位数*/
    options.c_cflag &= ~CSIZE;
    switch (databits)
    {
    case 7:
        options.c_cflag |= CS7;
        break;
    case 8:
        options.c_cflag |= CS8;
        break;
    default:
        ERROR ("Unsupported data size");
        return -1;
    }

    switch (parity)
    {
    case 'n':
    case 'N':
        options.c_cflag &= ~PARENB;   /* Clear parity enable */
        options.c_iflag &= ~INPCK;     /* Enable parity checking */
        break;
    case 'o':
    case 'O':
        options.c_cflag |= (PARODD | PARENB);  /* 设置为奇效验*/
        options.c_iflag |= INPCK;             /* Disnable parity checking */
        break;
    case 'e':
    case 'E':
        options.c_cflag |= PARENB;     /* Enable parity */
        options.c_cflag &= ~PARODD;   /* 转换为偶效验*/
        options.c_iflag |= INPCK;       /* Disnable parity checking */
        break;
    case 'S':
    case 's':  /*as no parity*/
        options.c_cflag &= ~PARENB;
        options.c_cflag &= ~CSTOPB;
        break;
    default:
        ERROR ("Unsupported parity");
        return -1;
    }

    /* 设置停止位*/
    switch (stopbits)
    {
    case 1:
        options.c_cflag &= ~CSTOPB;
        break;
    case 2:
        options.c_cflag |= CSTOPB;
        break;
    default:
        ERROR ("Unsupported stop bits");
        return -1;
    }

    /* Set input parity option */
    //if (parity != 'n')
    //  options.c_iflag |= INPCK;

    options.c_cc[VINTR] = 0;
    options.c_cc[VQUIT] = 0;
    options.c_cc[VERASE] = 0;
    options.c_cc[VKILL] = 0;
    options.c_cc[VEOF] = 0;
    options.c_cc[VTIME] = 1;
    options.c_cc[VMIN] = 0;
    options.c_cc[VSWTC] = 0;
    options.c_cc[VSTART] = 0;
    options.c_cc[VSTOP] = 0;
    options.c_cc[VSUSP] = 0;
    options.c_cc[VEOL] = 0;
    options.c_cc[VREPRINT] = 0;
    options.c_cc[VDISCARD] = 0;
    options.c_cc[VWERASE] = 0;
    options.c_cc[VLNEXT] = 0;
    options.c_cc[VEOL2] = 0;
    //options.c_cc[VTIME] = 150; // 15 seconds
    //options.c_cc[VMIN] = 0;

    tcflush (fd,TCIFLUSH); /* Update the options and do it NOW */
    if ((status = tcsetattr (fd,TCSANOW,&options)) != 0) {
        ERROR ("fail: status=%d, %s", status, strerror (errno));
        return -1;
    }
    return 0;
}

3，在一定超时时间内读取数据

static int cmd_read_timeout (int fd, unsigned char* buf, int msec) {
    if (fd < 0 || buf == NULL) {
        ERROR ("fd = %d, buf=%p", fd, buf);
        return -1;
    }

    int maxfd = fd;
    fd_set fdread;

    FD_ZERO (&fdread);
    FD_SET (fd, &fdread);

    /* set a suitable timeout to play around with */
    struct timeval timeout;
    timeout.tv_sec = 0;
    timeout.tv_usec = msec*1000;

    int nread = 0;
    int rc = select (maxfd+1, &fdread, NULL, NULL, &timeout);
    switch (rc) {
    case -1:
        ERROR ("error: %s", strerror (errno));
        /* select error */
        nread = -1;
        break;
    case 0:
        //DEBUG ("timeout!");
        nread = -1;
        break;
    default:
    {
        /* readable sockets */
        if (FD_ISSET (fd, &fdread)) {
            nread = read (fd, buf, 512);
            //DEBUG ("read(%d):%s\n", nread, buf);
            if ((buf[1] + 2) == nread) {
                // checksum
                unsigned char checksum = 0;
                for (int i = 0; i < nread; i++) {
                    checksum = checksum^buf[i];
                }
                if (checksum == 0) {
                    // get right command.
                } else {
                    nread = 0;
                }
            } else {
                // ERROR cmd lenght;
                DEBUG ("cmd length not right! got data len=%d, require=%d", nread, buf[1]+2);
                nread = 0;
            }
        } else {
            ERROR ("fd not set! maybe error!");
            nread = -1;
        }
        break;
    }
    }
    return nread;
}

4，读取唯一的卡号和sector0上block1的数据。

//============================================
//  Command List, preamble + length + command
//============================================
static const unsigned char SelectCard[]=      {0xBA,0x02,0x01 };
static const unsigned char LoginSector0[]=    {0xBA,0x0A,0x02,0x00,0xAA,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF};
static const unsigned char LoginSector1[]=    {0xBA,0x0A,0x02,0x01,0xAA,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF};
static const unsigned char ReadBlock1[]=      {0xBA,0x03,0x03,0x01};
static const unsigned char WriteBlock1[]=     {0xBA,0x13,0x04,0x01,0x00,0x11,0x22,0x33,0x44,0x55,0x66,0x77,0x88,0x99,0xAA,0xBB,0xCC,0xDD,0xEE,0xFF};
static const unsigned char ReadValue[]=       {0xBA,0x03,0x05,0x05};
static const unsigned char InitializeValue[]=   {0xBA,0x07,0x06,0x04,0x00,0x00,0x00,0x01};
static const unsigned char IncrementValue[]=  {0xBA,0x07,0x08,0x04,0x00,0x00,0x00,0x20};
static const unsigned char DecrementValue[]=  {0xBA,0x07,0x09,0x04,0x03,0x00,0x00,0x00};
static const unsigned char CopyValue[]=       {0xBA,0x04,0x0A,0x04,0x05};
static const unsigned char ReadULPage5[]=     {0xBA,0x03,0x10,0x05};
static const unsigned char WriteULPage5[]=    {0xBA,0x07,0x11,0x05,0x11,0x22,0x33,0x44};
static const unsigned char TurnOnRedLed[]=    {0xBA,0x03,0x40,0x01};
static const unsigned char TurnOffRedLed[]=   {0xBA,0x03,0x40,0x00};

static int wrap_data (unsigned char* dest, const unsigned char* src, int len) {
    if (dest == NULL || src == NULL || len == 0) return -1;
    memcpy (dest, src, len);
    unsigned char checksum = 0;
    for (int i = 0; i < len; i++) {
        checksum = checksum ^ src[i];
    }
    dest[len] = checksum;
    return 0;
}

int clear_comm (int fd) {
    tcflush(fd,TCIFLUSH);
    return 0;
}

int read_card_id_name (int fd, unsigned char* id, unsigned char* name) {
    if (id == NULL || name == NULL) return -1;
    unsigned char data_send[512] = {0};
    unsigned char data_recv[512] = {0};
    int nWrite = 0;
    int nRead = 0;

    tcflush(fd,TCIFLUSH);

    wrap_data (data_send, SelectCard, sizeof (SelectCard));
    nWrite = write (fd, data_send, sizeof (SelectCard) + 1);
    if ((nRead = cmd_read_timeout (fd, data_recv, 300)) <= 0) {
        return -1;
    }
    //DEBUG ("(%d) %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x", nRead, data_recv[0], data_recv[1], data_recv[2], data_recv[3], data_recv[4], data_recv[5], data_recv[6], data_recv[7], data_recv[8], data_recv[9]);
    if ((data_recv[2] != 0x01) || (data_recv[3] != 0)) {
        return -1;
    }

    int retcode = 0;
    unsigned char card_type = data_recv[data_recv[1]];
    switch (card_type) {
    case 1:
    case 4:
        memcpy (id, &data_recv[4], 4);
#if 1
        // verify password of sector0
        wrap_data (data_send, LoginSector0, sizeof (LoginSector0));
        nWrite = write (fd, data_send, sizeof (LoginSector0) + 1);
        if ((nRead = cmd_read_timeout (fd, data_recv, 300)) <= 0) {
            return -1;
        }
        if ((data_recv[2] != 0x02) || (data_recv[3] != 0x02)) {
            return -1;
        }

        // read data from block1
        wrap_data (data_send, ReadBlock1, sizeof (ReadBlock1));
        nWrite = write (fd, data_send, sizeof (ReadBlock1) + 1);
        if ((nRead = cmd_read_timeout (fd, data_recv, 300)) <= 0) {
            return -1;
        }
        if ((data_recv[2] != 0x03) || (data_recv[3] != 0)) {
            return -1;
        }
        memcpy (name, &data_recv[4], 16);
#endif
        retcode = 0;
        break;
    case 3:
        memcpy (id, &data_recv[4], 7);
        retcode = -1;
        break;
    case 2:
    case 5:
    case 6:
    default:
        retcode = -1;
        break;
    }
    if (retcode != 0) {
        return retcode;
    }
    // Glare Red Led to indicate working ok
    wrap_data (data_send, TurnOnRedLed, sizeof (TurnOnRedLed));
    nWrite = write (fd, data_send, sizeof (TurnOnRedLed) + 1);
    nRead = cmd_read_timeout (fd, data_recv, 300);
    usleep (200*1000);
    wrap_data (data_send, TurnOffRedLed, sizeof (TurnOffRedLed));
    nWrite = write (fd, data_send, sizeof (TurnOffRedLed) + 1);
    nRead = cmd_read_timeout (fd, data_recv, 300);

    return 0;
}

5，闪烁红灯，提示操作成功。

int GlareLed (int fd) {
    int retcode = 0;
    unsigned char data_send[512] = {0};
    unsigned char data_recv[512] = {0};
    int nWrite = 0;
    int nRead = 0;

    // Glare Red Led to indicate working ok
    wrap_data (data_send, TurnOnRedLed, sizeof (TurnOnRedLed));
    nWrite = write (fd, data_send, sizeof (TurnOnRedLed) + 1);
    nRead = cmd_read_timeout (fd, data_recv, 300);
    DEBUG ("get %d bytes", nRead);
    usleep (200*1000);
    wrap_data (data_send, TurnOffRedLed, sizeof (TurnOffRedLed));
    nWrite = write (fd, data_send, sizeof (TurnOffRedLed) + 1);
    nRead = cmd_read_timeout (fd, data_recv, 300);
    DEBUG ("get %d bytes", nRead);
    return 0;
}

6，主函数

int main(int argc, char **argv)
{
    const char *dev ="/dev/ttyUSB0";
    if (argc > 1) dev = argv[1];

    int fd = open (dev, O_RDWR|O_NOCTTY|O_NDELAY);         //| O_NOCTTY | O_NDELAY
    if (fd < 0) {
        ERROR ("Can't Open Serial Port");
        return -1;
    }
    if (set_options (fd, B115200, 8, 1, 'N') != 0) {
        ERROR ("Set Parity Error");
        close (fd);
        return -1;
    }

    while (1) {
        unsigned char id[10];
        unsigned char name[20];
        int ret = read_card_id_name (fd, id, name);
        if (ret == 0) {
            printf ("%02x%02x%02x%02x\n ", id[0], id[1], id[2], id[3]);
        }
        //GlareLed (fd);
        //DEBUG ("");
        //string content = getdata (fd);
        //printf ("%s", content.c_str ());
        //write(fd, "AT1", 3);
        usleep (300*1000);
    }
    close(fd);
    return 0;
}

7，遇到问题
在开发过程中，发现在嵌入式环境中，接收的数据经常会莫名丢失，0x13，0x11经常会不见了，丢失的都是这两个数，后来加上如下这段就好了。

    options.c_cc[VINTR] = 0;
    options.c_cc[VQUIT] = 0;
    options.c_cc[VERASE] = 0;
    options.c_cc[VKILL] = 0;
    options.c_cc[VEOF] = 0;
    options.c_cc[VTIME] = 1;
    options.c_cc[VMIN] = 0;
    options.c_cc[VSWTC] = 0;
    options.c_cc[VSTART] = 0;
    options.c_cc[VSTOP] = 0;
    options.c_cc[VSUSP] = 0;
    options.c_cc[VEOL] = 0;
    options.c_cc[VREPRINT] = 0;
    options.c_cc[VDISCARD] = 0;
    options.c_cc[VWERASE] = 0;
    options.c_cc[VLNEXT] = 0;
    options.c_cc[VEOL2] = 0;

8，有问题可以联系 [email protected]