Linux下RFID卡（門禁卡，Mifare卡）的編程

我使用的是串口讀卡器，RFID卡是philips的Mifare-M1卡。操作讀卡器，就是操作串口設備。串口設備的基礎只是，請參考 https://www.ibm.com/developerworks/cn/linux/l-serials/ ，此文講得很詳細。

在嵌入式平台下，串口設置需要做得更全一些，以避免一些特殊字符問題。本文描述了一種用select進行非阻塞方式讀取的方法，方便了應用程序進行整合。

1，打開串口

1. int open_comm (const char* device) {
2. if (device == NULL) return -1;
3. int fd = open (device, O_RDWR|O_NOCTTY|O_NDELAY);
4. return fd;
5. }

1. static int speed_arr[] = {B115200, B38400, B19200, B9600, B4800, B2400, B1200, B300,
2. B38400, B19200, B9600, B4800, B2400, B1200, B300, };
3. static int name_arr[] = { 115200, 38400, 19200, 9600, 4800, 2400, 1200, 300,
4. 38400, 19200, 9600, 4800, 2400, 1200, 300, };
6. int set_options (int fd, int speed, int databits, int stopbits, int parity) {
7. struct termios options;
8. int status = 0;
9. if ((status = tcgetattr (fd, &options)) != 0) {
10. ERROR ("fail: status=%d, %s", status, strerror (errno));
11. return -1;
12. }
14. int bSpeed = -1;
15. for (int i = 0; i < sizeof(speed_arr) / sizeof(int); i++) {
16. if (speed == name_arr[i]) {
17. bSpeed = speed_arr[i];
18. break;
19. }
20. }
21. if (bSpeed == -1) {
22. ERROR ("wrong speed=%d", speed);
23. return -1;
24. }
25. cfsetispeed (&options, bSpeed);
26. cfsetospeed (&options, bSpeed);
28. /*允許接收並且設置為本地模式*/
29. options.c_cflag |= (CLOCAL|CREAD);
31. /*設置數據位數*/
32. options.c_cflag &= ~CSIZE;
33. switch (databits)
34. {
35. case 7:
36. options.c_cflag |= CS7;
37. break;
38. case 8:
39. options.c_cflag |= CS8;
40. break;
41. default:
42. ERROR ("Unsupported data size");
43. return -1;
44. }
46. switch (parity)
47. {
48. case 'n':
49. case 'N':
50. options.c_cflag &= ~PARENB; /* Clear parity enable */
51. options.c_iflag &= ~INPCK; /* Enable parity checking */
52. break;
53. case 'o':
54. case 'O':
55. options.c_cflag |= (PARODD | PARENB); /* 設置為奇效驗*/
56. options.c_iflag |= INPCK; /* Disnable parity checking */
57. break;
58. case 'e':
59. case 'E':
60. options.c_cflag |= PARENB; /* Enable parity */
61. options.c_cflag &= ~PARODD; /* 轉換為偶效驗*/
62. options.c_iflag |= INPCK; /* Disnable parity checking */
63. break;
64. case 'S':
65. case 's': /*as no parity*/
66. options.c_cflag &= ~PARENB;
67. options.c_cflag &= ~CSTOPB;
68. break;
69. default:
70. ERROR ("Unsupported parity");
71. return -1;
72. }
74. /* 設置停止位*/
75. switch (stopbits)
76. {
77. case 1:
78. options.c_cflag &= ~CSTOPB;
79. break;
80. case 2:
81. options.c_cflag |= CSTOPB;
82. break;
83. default:
84. ERROR ("Unsupported stop bits");
85. return -1;
86. }
88. /* Set input parity option */
89. //if (parity != 'n')
90. // options.c_iflag |= INPCK;
92. options.c_cc[VINTR] = 0;
93. options.c_cc[VQUIT] = 0;
94. options.c_cc[VERASE] = 0;
95. options.c_cc[VKILL] = 0;
96. options.c_cc[VEOF] = 0;
97. options.c_cc[VTIME] = 1;
98. options.c_cc[VMIN] = 0;
99. options.c_cc[VSWTC] = 0;
100. options.c_cc[VSTART] = 0;
101. options.c_cc[VSTOP] = 0;
102. options.c_cc[VSUSP] = 0;
103. options.c_cc[VEOL] = 0;
104. options.c_cc[VREPRINT] = 0;
105. options.c_cc[VDISCARD] = 0;
106. options.c_cc[VWERASE] = 0;
107. options.c_cc[VLNEXT] = 0;
108. options.c_cc[VEOL2] = 0;
109. //options.c_cc[VTIME] = 150; // 15 seconds
110. //options.c_cc[VMIN] = 0;
112. tcflush (fd,TCIFLUSH); /* Update the options and do it NOW */
113. if ((status = tcsetattr (fd,TCSANOW,&options)) != 0) {
114. ERROR ("fail: status=%d, %s", status, strerror (errno));
115. return -1;
116. }
117. return 0;
118. }