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  1. #include <stdio.h>
  2.  
  3. #define RFID_AS_CRC_TABLE_SIZE    256
  4. #define RFID_AS_MSB_16            (1<<15)
  5. #define RFID_AS_MSB_8             (1<<7)
  6. #define RFID_AS_BYTE_LEN           8
  7. #define RFID_AS_CRC5_LEN           5
  8. #define RFID_AS_CRC16_LEN          16
  9. #define RFID_AS_CRC5_POLYNOMIAL   (0x9)
  10. #define RFID_AS_CRC16_POLYNOMIAL  (0x1021)
  11. #define RFID_AS_CRC5_POLYNOMIAL_BMSK ((1<<RFID_AS_CRC5_LEN)-1)
  12. #define RFID_AS_CRC5_SEED (0x9)
  13. #define RFID_AS_CRC16_SEED (0xFFFF)
  14. #define RFID_AS_CRC5_RESIDUAL 0x0
  15. #define RFID_AS_CRC16_RESIDUAL (0xFFFF-0x1D0F)
  16.  
  17. typedef struct
  18. {
  19.   unsigned int                                                  TRext:1;
  20.   unsigned int                                                  M:2;
  21.   unsigned int                                                  DR:1;
  22.   unsigned int                                                  Command:4; // end of byte 0
  23.   unsigned int                                                  Q_high:3;
  24.   unsigned int                                                  Target:1;
  25.   unsigned int                                                  Session:2;
  26.   unsigned int                                                  Sel:2; // end of byte 1
  27.   unsigned int                                                  reserved_0:2;
  28.   unsigned int                                                  CRC:5;
  29.   unsigned int                                                  Q_low:1; // end of byte 2
  30.   unsigned int                                                  reserved_1:8;
  31. } query_cmd_s;
  32.  
  33. unsigned char rfid_as_crc5_table[RFID_AS_CRC_TABLE_SIZE];
  34. unsigned short rfid_as_crc16_table[RFID_AS_CRC_TABLE_SIZE];
  35.  
  36. void rfid_crc5_init()
  37. {
  38.   unsigned char bit_pos, remainder;
  39.   unsigned short byte_val;
  40.  
  41.   for(byte_val = 0; byte_val < RFID_AS_CRC_TABLE_SIZE; byte_val++)
  42.   {
  43.     remainder = byte_val;
  44.  
  45.     for(bit_pos = 0; bit_pos < RFID_AS_BYTE_LEN; bit_pos++)
  46.     {
  47.       if(remainder & RFID_AS_MSB_8)
  48.       {
  49.         remainder = (remainder << 1) ^ (RFID_AS_CRC5_POLYNOMIAL << (RFID_AS_BYTE_LEN - RFID_AS_CRC5_LEN));
  50.       }
  51.       else
  52.       {
  53.         remainder = remainder << 1;
  54.       }
  55.     }
  56.  
  57.     rfid_as_crc5_table[byte_val] = remainder >> (RFID_AS_BYTE_LEN - RFID_AS_CRC5_LEN);
  58.  
  59. #if 0    
  60.     printf("0x%02x, ", rfid_as_crc5_table[byte_val]);
  61.     if((byte_val + 1)%8 == 0)
  62.     printf("\n");
  63. #endif
  64.   }
  65.  
  66.   return;
  67. }
  68.  
  69. void rfid_crc16_init()
  70. {
  71.   unsigned char  bit_pos;
  72.   unsigned short byte_val, remainder;
  73.  
  74.  
  75.   for(byte_val = 0; byte_val < RFID_AS_CRC_TABLE_SIZE; byte_val++)
  76.   {
  77.     remainder = byte_val << (RFID_AS_CRC16_LEN-RFID_AS_BYTE_LEN);
  78.  
  79.     for(bit_pos = 0; bit_pos < RFID_AS_BYTE_LEN; bit_pos++)
  80.     {
  81.       if(remainder & RFID_AS_MSB_16)
  82.       {
  83.         remainder = (remainder << 1) ^ RFID_AS_CRC16_POLYNOMIAL;
  84.       }
  85.       else
  86.       {
  87.         remainder = remainder << 1;
  88.       }
  89.     }
  90.  
  91.     rfid_as_crc16_table[byte_val] = remainder;
  92.  
  93. #if 0
  94.     printf("0x%04x, ", rfid_as_crc16_table[byte_val]);
  95.     if((byte_val + 1)%8 == 0)
  96.     printf("\n");
  97. #endif
  98.   }
  99.  
  100.   return;
  101. }
  102.  
  103. unsigned char rfid_crc5_cal
  104. (
  105.   unsigned char *buf_ptr,
  106.   unsigned short bit_len
  107. )
  108. {
  109.   unsigned char crc5, last_byte;
  110.  
  111.   for(crc5 = RFID_AS_CRC5_SEED; bit_len >= RFID_AS_BYTE_LEN; bit_len -= RFID_AS_BYTE_LEN, buf_ptr++)
  112.   {
  113.     crc5 = rfid_as_crc5_table[(crc5 << (RFID_AS_BYTE_LEN-RFID_AS_CRC5_LEN)) ^ *buf_ptr];
  114.   }
  115.  
  116.   if(bit_len !=0)
  117.   {
  118.     last_byte = *buf_ptr;
  119.  
  120.     while(bit_len-- != 0)
  121.     {
  122.       if(((crc5 << (RFID_AS_BYTE_LEN - RFID_AS_CRC5_LEN)) ^ last_byte) & RFID_AS_MSB_8)
  123.       {
  124.         crc5 = ((crc5 << 1) ^ RFID_AS_CRC5_POLYNOMIAL) & RFID_AS_CRC5_POLYNOMIAL_BMSK;
  125.       }
  126.       else
  127.       {
  128.         crc5 = (crc5 << 1) & RFID_AS_CRC5_POLYNOMIAL_BMSK;
  129.       }
  130.  
  131.       last_byte <<= 1;
  132.     }
  133.   }
  134.  
  135.   return crc5;
  136. }
  137.  
  138. unsigned short rfid_crc16_cal
  139. (
  140.   unsigned char *buf_ptr,
  141.   unsigned short bit_len
  142. )
  143. {
  144.   unsigned short crc16, last_byte;
  145.  
  146.   for(crc16 = RFID_AS_CRC16_SEED; bit_len >= RFID_AS_BYTE_LEN; bit_len -= RFID_AS_BYTE_LEN, buf_ptr++)
  147.   {
  148.     crc16 = rfid_as_crc16_table[(crc16 >> (RFID_AS_CRC16_LEN - RFID_AS_BYTE_LEN)) ^ *buf_ptr] ^ (crc16 << RFID_AS_BYTE_LEN);
  149.   }
  150.  
  151.   if(bit_len !=0)
  152.   {
  153.     last_byte = (*buf_ptr) << (RFID_AS_CRC16_LEN - RFID_AS_BYTE_LEN);
  154.  
  155.     while(bit_len-- != 0)
  156.     {
  157.       if((crc16 ^ last_byte) & RFID_AS_MSB_16)
  158.       {
  159.         crc16 = (crc16 << 1) ^ RFID_AS_CRC16_POLYNOMIAL;
  160.       }
  161.       else
  162.       {
  163.         crc16 = crc16 << 1;
  164.       }
  165.  
  166.       last_byte <<= 1;
  167.     }
  168.   }
  169.  
  170.   return ~crc16;
  171. }
  172.  
  173. void main()
  174. {
  175.     rfid_crc5_init();
  176.     rfid_crc16_init();
  177.  
  178.     unsigned char data[] = {0x80,0xb6,0xa4,0x41,0xec,0xB2,0xDD,0xD9,0x01,0x40, 0xC4, 0xF3};
  179.  
  180.     unsigned short crc = rfid_crc16_cal(data, 41);
  181.  
  182.     printf("crc 0x%x \n", crc);
  183. }
  184.  
Success #stdin #stdout 0s 5284KB
comments (?)
stdin 
45
stdout 
crc 0xf2d1
https://ideone.com/34KXq9
language:
C (gcc 8.3)
created:
3 hours ago
visibility:
public

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