Modbus Rtu Crc16 Calculation

I'm coding a MODBUS CRC16 calculator in C. What I have before is a python that do this, I wanted to convert it to C. I found some codes online but it's not giving me the correct an

Solution 1:

• WORD should be unsigned short (2 bytes), not unsigned long (4 or 8 bytes depended on platform)

  typedefunsignedshort WORD;
  

• As @paddy said, loop from 0 to 6 in the for loop:

  for (i=0; i<6; i++) {
      ...
  }
  

• crc_data should be of type WORD, not char

  WORD crc_data;
  

• use %04x in last printf()

  printf("this is CRC: %04x\n", crc_data);