Implementation of CRC16 ISO 13239

Question

I am trying to implement Crc16 in C #. I have already tried many different implementations, but most of them give me different meanings. Here are some of the codes I've already used.

private static int POLYNOMIAL = 0x8408; private static int PRESET_VALUE = 0xFFFF; public static int crc16(byte[] data) { int current_crc_value = PRESET_VALUE; for (int i = 0; i < data.Length; i++) { current_crc_value ^= data[i] & 0xFF; for (int j = 0; j < 8; j++) { if ((current_crc_value & 1) != 0) { current_crc_value = (current_crc_value >> 1) ^ POLYNOMIAL; } else { current_crc_value = current_crc_value >> 1; } } } current_crc_value = ~current_crc_value; return current_crc_value & 0xFFFF; } 

this is another implementation i used but both give different values

  const ushort polynomial = 0xA001; ushort[] table = new ushort[256]; public ushort ComputeChecksum(byte[] bytes) { ushort crc = 0; for (int i = 0; i < bytes.Length; ++i) { byte index = (byte)(crc ^ bytes[i]); crc = (ushort)((crc >> 8) ^ table[index]); } return crc; } public byte[] ComputeChecksumBytes(byte[] bytes) { ushort crc = ComputeChecksum(bytes); return BitConverter.GetBytes(crc); } public Crc16() { ushort value; ushort temp; for (ushort i = 0; i < table.Length; ++i) { value = 0; temp = i; for (byte j = 0; j < 8; ++j) { if (((value ^ temp) & 0x0001) != 0) { value = (ushort)((value >> 1) ^ polynomial); } else { value >>= 1; } temp >>= 1; } table[i] = value; } } 

The value I am using is Octet String "[jp3] TEST [fl] Flashes [/ fl]" , and its expected value is 95F9 in hexadecimal format. This is an example of NTCIP.

thanks

Answer 1

It:

 static readonly ushort[] fcstab = new ushort[] { 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 }; static ushort compute_fcs(byte[] data) { return compute_fcs(data, 0, data.Length); } static ushort compute_fcs(byte[] data, int start, int length) { ushort fcs = 0xFFFF; int end = start + length; for (int i = start; i < end; i++) { fcs = (ushort)(((ushort)(fcs >> 8)) ^ fcstab[(fcs ^ data[i]) & 0xFF]); } return (ushort)(~fcs); } static void Main(string[] args) { byte[] pattern = new byte[] { 0x02, 0x07, 0x01, 0x03, 0x01, 0x02, 0x00, 0x34, 0x07, 0x07, 0x1C, 0x59, 0x34, 0x6F, 0xE1, 0x83, 0x00, 0x00, 0x41, 0x06, 0x06, 0x7B, 0x3C, 0xFF, 0xCF, 0x3C, 0xC0 }; // http://www.ite.org/standards/1203v03-04%20Part%201%20dms2011.pdf // Page 158, CRC = 0x52ED ushort fcs = compute_fcs(pattern); // 0x52ED } 

will work only for this test http://www.ite.org/standards/1203v03-04%20Part%201%20dms2011.pdf (about p. 158, CRC = 0x52ED ).

For example, a PDF line, as written on some pages later:

"Indicates a CRC-16 value (polynomial defined in ISO / IEC 3309) created using dmsMessageMultiString (MULTI-Message), dmsMessageBeacon and dmsMessagePixelService objects in the specified order, not including OER fields or lengths. Note that the calculation should accept the value 0 (0) for the dmsMessageBeacon object and / or for dmsMessagePixelService if they are not supported

(in italics)

So:

 string str = "[jp3]TEST [fl]Flashing[/fl]"; var bytes = Encoding.ASCII.GetBytes(str); Array.Resize(ref bytes, bytes.Length + 2); // Note that these two rows are useless, because the Array.Resize will have already filled with 0 bytes[bytes.Length - 2] = 0; // dmsMessageBeacon bytes[bytes.Length - 1] = 0; // dmsMessagePixelService ushort fcs2 = compute_fcs(bytes); // 0xF995 var bytes2 = BitConverter.GetBytes(fcs2); // 0x95 0xF9 

This shows that the protocol is not numerous (like my computer, this is Intel). In fact, the CRC-16 string has a value of 0xF995, but these 16 bits in memory are displayed as 0x95 0xF9 (as in the example where single bytes are shown).

Answer 2

There are many CRC-16 calculation algorithms.

For instance:

• The CRC-16-IBM, which is used in the Modbus protocol, USB, etc., is the most popular.
• CRC-16-CCITT is used in Bluetooth.

I use CRC-16-IBM in my applications that work with industrial controllers.

 public static UInt16 FastCRC16(byte[] Buffer, UInt16 ui_length) { UInt16[] crc_table = { 0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241, 0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440, 0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40, 0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841, 0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40, 0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41, 0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641, 0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040, 0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240, 0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441, 0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41, 0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840, 0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41, 0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40, 0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640, 0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041, 0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240, 0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441, 0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41, 0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840, 0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41, 0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40, 0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640, 0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041, 0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241, 0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440, 0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40, 0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841, 0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40, 0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41, 0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641, 0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040}; UInt16 Crc = 65535; UInt16 x; for (UInt16 i = 0; i < ui_length; i++) { x = (UInt16)(Crc ^ Buffer[i]); Crc = (UInt16)((Crc >> 8) ^ crc_table[x & 0x00FF]); } return Crc; }