What the lack of CRC-CCITT (0xFFFF)?

Question

基于在线CRC计算，当我输入十六进制字符串data =

503002080000024400003886030400000000010100

I get result CRC-CCITT (0xFFFF) =

0x354E(预期结果)

.

我使用下面的代码，但是CalcCRC16()的结果是0xACEE。下面缺少什么脚本?

using System;
using System.Windows.Forms;
using System.Runtime.Remoting.Metadata.W3cXsd2001;
using System.Diagnostics;
namespace WindowsFormsApplication1 {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e) {
            string result = CalcCRC16("503002080000024400003886030400000000010100");            
            Debug.Print(result);
            // result = ACEE
            // result expected = 354E
        }
        // CRC-CCITT (0xFFFF) with poly 0x1021
        // input (hex string) =  "503002080000024400003886030400000000010100"
        // result expected (hex string) = "354E"
        public string CalcCRC16(string strInput) {
            ushort temp = 0;
            ushort crc = 0xFFFF;
            byte[] bytes = GetBytesFromHexString(strInput);
            for (int j = 0; j < bytes.Length; j++) {
                crc = (ushort)(crc ^ bytes[j]);
                for (int i = 0; i < 8; i++) {
                    if ((crc & 0x0001) == 1)
                        crc = (ushort)((crc >> 1) ^ 0x1021);
                    else
                        crc >>= 1;
                }
            }
            crc = (ushort)~(uint)crc;
            temp = crc;
            crc = (ushort)((crc << 8) | (temp >> 8 & 0xFF));
            return crc.ToString("X4");
        }
        public Byte[] GetBytesFromHexString(string strInput) {
            Byte[] bytArOutput = new Byte[] { };
            if (!string.IsNullOrEmpty(strInput) && strInput.Length % 2 == 0) {
                SoapHexBinary hexBinary = null;
                try {
                    hexBinary = SoapHexBinary.Parse(strInput);
                    if (hexBinary != null)
                        bytArOutput = hexBinary.Value;
                }
                catch (Exception ex) {
                    MessageBox.Show(ex.Message);
                }
            }
            return bytArOutput;
        }
    }
}

Answer 1

我找到了答案，我将在这里分享。可能对别人有用。

strInput = 503002080000024400003886030400000000010100

initial = 0xFFFF

poly = 0x1021

strOutput = 354E

reference = Online CRC Calc

public string CalcCRC16(string strInput) {
    ushort crc = 0xFFFF;
    byte[] data = GetBytesFromHexString(strInput);
    for (int i = 0; i < data.Length; i++) {
        crc ^= (ushort)(data[i] << 8);
        for (int j = 0; j < 8; j++) {
            if ((crc & 0x8000) > 0)
                crc = (ushort)((crc << 1) ^ 0x1021);
            else
                crc <<= 1;
        }
    }
    return crc.ToString("X4");
}
public Byte[] GetBytesFromHexString(string strInput) {
    Byte[] bytArOutput = new Byte[] { };
    if (!string.IsNullOrEmpty(strInput) && strInput.Length % 2 == 0) {
        SoapHexBinary hexBinary = null;
        try {
            hexBinary = SoapHexBinary.Parse(strInput);
            if (hexBinary != null) {
                bytArOutput = hexBinary.Value;
            }
        }
        catch (Exception ex) {
            MessageBox.Show(ex.Message);
        }
    }
    return bytArOutput;
}

Answer 2

下面是一个在我的应用程序中工作的示例。我有点挣扎，现在我知道这是因为我不得不使用char ptrs而不是16位int指针(因为CCIT是LSB顺序优先，所以我们从缓冲区中选择1个字节，将其移位8次使其变为16位以验证上MSB位0x8000)。

当人们与16位CRC斗争时发现的大多数原因(而大多数情况下8位有效):

• Buffer应该被8bit ptr
调用
• 在异或之前移动!
永远不要使用int或unsigned int..但要用短!我的应用程序运行在16位和32位Microchip PIC上，使用整数在16位PIC上产生16位值，在32位平台上产生32位值(这么多零!)。

BOOL = unsigned char。UINT16 = unsigned short;该函数在代码中运行，因此不是while/forloop。完成后，CRC被复制到* CRC所指向的地址。这样所有其他任务(M95调制解调器，MCP的I2C, Flash日志，TCP/IP等)将不会有太大的延迟。

BOOL CRC_16(UINT16 ui16_Bytes, char *src, UINT16 *crc)
{    
    static BOOL bNew = FALSE;
    static UINT16  remainder = 0;   
    static UINT16 i = 0;
    static UINT16 ui16_Loc_bytes;
    static char *ptr;
    static char locData;
    if(!bNew)
    {
    ui16_Loc_bytes = ui16_Bytes;
    ptr = src;
    locData = *ptr;
    i = 8;
    remainder = 0x0000;
    bNew = TRUE;
    }
    if(ui16_Loc_bytes)
    {
    if(i == 8)
    {
        remainder ^= (((UINT16)locData)<<8);                //Only 8bits at a time filled with zeros
    }
    if(i)
    {
        if (remainder & 0x8000)
        {
        remainder = (remainder << 1);
        remainder ^= POLYNOMIAL_16;
        }
        else
        {       
        remainder = (remainder << 1);
        }       
        i--;
    }
    else
    {
        ui16_Loc_bytes--;
        ptr++;
        locData = *ptr;
        //ptr++;
        i = 8;
    }
    }
    else
    {
    bNew = FALSE;
    *crc = remainder;
    return TRUE;
    }
    return FALSE;
}

if(SDKaart.ui16_RecBytes >= SDKaart.ui16_ByteLen)//30-5-2018 edited SDKaart.CMD[SDKaart.ui8_ActiefCMD].ui16_RecLen)
                    {
                    SD_DESELECT;
                    if(SDKaart.bInitReady && SDKaart.b_BlockRead)
                    {
                        if(CRC_16(512,(char*)&SDKaart.Mem_Block.SD_Buffer[0], &SDKaart.ui16_MemBlock_CRC))
                        {                       
                        if((((UINT16)SDKaart.Mem_Block.SD_Buffer[512]<<8)|(UINT16)SDKaart.Mem_Block.SD_Buffer[513]) == SDKaart.ui16_MemBlock_CRC)
                        {
                            SDKaart.bRXReady = TRUE;
                            SDKaart.TXStat = SPI_IDLE;
                            printf("CRC16 OK %xrn",SDKaart.ui16_MemBlock_CRC);
                        }
                        else
                        {
                            SDKaart.bRXReady = TRUE;
                            SDKaart.TXStat = SPI_IDLE;
                            printf("CRC16 %u != 0x%x 0x%xrn",SDKaart.ui16_MemBlock_CRC,SDKaart.Mem_Block.SD_Buffer[512], SDKaart.Mem_Block.SD_Buffer[513] );
                        }
                        //printf("CRC citt: %urn", Calculate_CRC_CCITT((char *)&SDKaart.Mem_Block.SD_Buffer[0],512));
                        }
                    }
                    else
                    {
                        SDKaart.bRXReady = TRUE;
                        SDKaart.TXStat = SPI_IDLE;
                    }
                    }
                    else
                    {                       
                    if(SD_SPI_TX_READY)
                    {
                        SDKaart.bNewSPIByte = TRUE;
                        SPI1BUF = SD_EMPTY_BYTE;                        
                    }
                }

我已经使用了许多在网上找到的crcs，但很多都不起作用。请注意，许多在线"示例"确实在XOR后面使用<<1，但必须在XOR之前完成。

POLY_16是0x1021。下一个机会是构建一个表选择器。:)

Greetz约翰。