C# ----串口开发之CRC校验码

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CRC 即循环冗余校验码(Cyclic Redundancy Check)

循环冗余校验码(CRC)的基本原理是:在K位信息码后再拼接R位的校验码,整个编码长度为N位,因此,这种编码也叫(N,K)码。对于一个给定的(N,K)码,可以证明存在一个最高次幂为N-K=R的多项式G(x)。根据G(x)可以生成K位信息的校验码,而G(x)叫做这个CRC码的生成多项式。 校验码的具体生成过程为:假设要发送的信息用多项式C(X)表示,将C(x)左移R位(可表示成C(x)*2R),这样C(x)的右边就会空出R位,这就是校验码的位置。用 C(x)*2R 除以生成多项式G(x)得到的余数就是校验码。

 

CRC校验码 涉及到位运算,比如 位异或(^)、位左移(<<)、位右移(>>);详细可参考C#位操作

CRC校验码示例1:

        #region CRC

        //===============================================

        //CRC校验计算

        //===============================================

        private void RsCrc(byte[] a, int n, out byte H, out byte L)   //传入要校验的数组 和要校验的数据个数

        {

            //A    01  03  01  (E1  30)

            //B    01  03  02  (A1  31)

            //C    01  03  03  (60  F1)

            //D    01  03  04  (21  33)



            int i = 0;                          //CRC循环中的索引

            int j = 0;                          //

            byte crc_h = 0xFF;                                //高CRC字节初始化

            byte crc_l = 0xFF;                                //低CRC字节初始化



            for (i = 0; i < n; i++)

            {

                //j = crc_h^a[i];   

                j = crc_h ^ a[i];

                crc_h = Convert.ToByte(crc_l ^ crc_tab_h[j]);

                crc_l = Convert.ToByte(crc_tab_l[j]);

            }

            H = crc_h;

            L = crc_l;

        }

        //===============================================

        //CRC校验表

        //===============================================

        private static byte[] crc_tab_h = {

                                           0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,

                                           0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,

                                           0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,

                                           0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,

                                           0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,

                                           0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,

                                           0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,

                                           0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,

                                           0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,

                                           0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,

                                           0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,

                                           0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,

                                           0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,

                                           0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,

                                           0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,

                                           0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,

                                           0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,

                                           0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,

                                           0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,

                                           0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,

                                           0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,

                                           0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,

                                           0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,

                                           0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,

                                           0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,

                                           0x80, 0x41, 0x00, 0xC1, 0x81, 0x40

                                          };



        private static byte[] crc_tab_l ={

                                          0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06,

                                          0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,

                                          0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,

                                          0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A,

                                          0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4,

                                          0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,

                                          0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,

                                          0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4,

                                          0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,

                                          0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29,

                                          0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED,

                                          0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,

                                          0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60,

                                          0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,

                                          0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,

                                          0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,

                                          0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E,

                                          0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,

                                          0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71,

                                          0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92,

                                          0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,

                                          0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B,

                                          0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,

                                          0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,

                                          0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42,

                                          0x43, 0x83, 0x41, 0x81, 0x80, 0x40

                                         };

        #endregion
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CRC校验码示例2:

        #region 计算CRC校验码

        /// <summary>

        /// 计算CRC校验码

        /// Cyclic Redundancy Check 循环冗余校验码

        /// 是数据通信领域中最常用的一种差错校验码

        /// 特征是信息字段和校验字段的长度可以任意选定

        /// </summary>

        /// <param name="data"></param>

        /// <returns></returns>

        public byte[] CRC16_C(byte[] data)

        {

            byte num = 0xff;

            byte num2 = 0xff;



            byte num3 = 1;

            byte num4 = 160;

            byte[] buffer = data;



            for (int i = 0; i < buffer.Length; i++)

            {

                //位异或运算

                num = (byte)(num ^ buffer[i]);



                for (int j = 0; j <= 7; j++)

                {

                    byte num5 = num2;

                    byte num6 = num;



                    //位右移运算

                    num2 = (byte)(num2 >> 1);

                    num = (byte)(num >> 1);



                    //位与运算

                    if ((num5 & 1) == 1)

                    {

                        //位或运算

                        num = (byte)(num | 0x80);

                    }

                    if ((num6 & 1) == 1)

                    {

                        num2 = (byte)(num2 ^ num4);

                        num = (byte)(num ^ num3);

                    }

                }

            }

            return new byte[] { num, num2 };

        }

        /// <summary>

        /// 转换为16进制字节数组

        /// </summary>

        /// <param name="hexString"></param>

        /// <returns></returns>

        private static byte[] strToHexByte(string hexString)

        {

            hexString = hexString.Replace(" ", "");

            //判断奇偶位数

            if ((hexString.Length % 2) != 0)

            {

                hexString = hexString + " ";

            }

            //声明字符串变量

            byte[] buffer = new byte[hexString.Length / 2];



            for (int i = 0; i < buffer.Length; i++)

            {

                //将指定基的数字的字符串表示形式转换为等效的8位无符号整数

                //即将字符串转换为16进制形式的字节

                buffer[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 0x10);

            }

            return buffer;

        }

        #endregion
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