问题描述
你好
我正在尝试从以下代码中计算出冗余校验字节，当?与！.交换
希望您能提供帮助！
步骤如下
计算LRC字节.
生成LRC的过程是:
添加消息中的所有字节，但开头的冒号"除外.所有进位都被丢弃.
LCR =-(8位值);两个人的补语
示例:
Packet [10]是一个10字节的char数组，分配如下:
数据包[0] =‘?'= 0x3F
封包[1] ="F" = 0x46
封包[2] =‘l’= 0x6C
封包[3] ='o'= 0x6F
封包[4] =’w’= 0x77
Packet [5] = 0//将是LRC的高字节
Packet [6] = 0//将是LRC的低字节
Packet [7] = 0//将返回回车； 0x0D
Packet [8] = 0//将作为换行符； 0x0A
Packet [9] = 0//C可选字节中的字符串终止符
packetLength = strlen(Packet)//packetLength = 5;
C解析为数组无符号字节LRC = 0的前0////以0 LRC值开始
For(i ＝ 0； i ＜packetLength； i ++)LRC ＝ LRC + Packet [i]； //将所有字节添加到LRC
对于此示例:LRC = 0x3F + 0x46 + 0x6C + 0x6F + 0x77 = 0x1D7(如果未舍弃进位)
LRC = 0xD7放弃了进位LRC = -LRC//两个补码
二进制补码是〜(0xD7)+ 1 = 0x28 +1 = 0x29(〜是非运算符)(有关非运算符或二进制补码的更多信息，请参阅Wikipedia)
现在将结果分为高位和低位2和9.
将这些值中的每一个都转换为等效的ASCII十六进制.
2-> 0x32
9-> 0x39
Packet [5] =转换为ASCII的LRC的高4位，2-> 0x32
数据包[6] ＝ LRC的低4位转换为ASCII，9-＞ 0. 0x39
Packet [7] = 0x0D//回车Packet [8] = 0x0A//换行
回顾:
1)在消息中添加所有字节
2)将NOT应用于结果并添加1(2的补数)
3)将字节分成高段和低段
4)将高低段转换为ASCII十六进制值
代码:
使用系统；
使用System.Collections.Generic;
使用System.Linq;
使用System.Text;
命名空间LabVIEWInterface
{
公共类Calcbyte
{
公共静态字节[] CalcLRC(字节[] cmnd)
{
int i，j，bSize = cmnd.Length;
uint lrc，高，低，CR，LF；
字符串temp;
byte []个字节=新的字节[(((bSize)+ 4)];
lrc = 0x00;
CR = 0x0d;
LF = 0x0a;
//循环遍历输入字节数组
对于(i = 0; i< cmnd.Length; i ++)
{
//求和消息字节
lrc = lrc +(uint)cmnd [i];
//将每个消息字节插入到结果中
bytes [i] = cmnd [i];
}
//删除剩余部分
如果(lrc> 256)
{
lrc = lrc-(uint)(256 * Math.Floor((double)lrc/256));
}
//对和执行2的补码
lrc =(ushort)(〜lrc);
lrc = lrc + 1;
//删除剩余部分
如果(lrc> 256)
{
lrc = lrc-(uint)(256 * Math.Floor((double)lrc/256));
}
//分为高低位
temp = lrc.ToString("X");
高=(uint)temp [0];
低=(uint)temp [1];
//将高，低，回车符和换行符插入结果
bytes [[bSize)] =(byte)high;
bytes [(bSize +1)] =(低)字节；
bytes [(bSize + 2)] =(byte)CR;
bytes [(bSize + 3)] =(byte)LF;
//返回具有输入，LRC，CR，LF的结果字节数组
返回字节；
}
}
}
Hello
I am trying to calculate redundancy check bytes from following code, the bytes does not change when ? is exchanged with !.
I hope you can help!
the procedure is as follows
Calculating the LRC bytes.
A procedure for generating an LRC is:
Add all bytes in the message, excluding the starting ‘colon’. All carries are discarded.
LCR = -(8 bit value ) ; two’s complement
Example:
Packet[10] is a 10 byte char array assigned as follows
Packet[0] = ‘?’ = 0x3F
Packet[1] =’F’ = 0x46
Packet[2]=’l’ =0x6C
Packet[3]=’o’ =0x6F
Packet[4]=’w’ =0x77
Packet[5]=0 // will be high byte of LRC
Packet[6]=0 // will be low byte of LRC
Packet[7]=0 // will be carriage return; 0x0D
Packet[8]=0 // will be line feed; 0x0A
Packet[9]=0 // string terminator in C optional byte
packetLength = strlen(Packet) // packetLength= 5;
C parses to first 0 in the array unsigned byte LRC=0 // start with 0 LRC value
For(i=0; i<packetLength; i++) LRC = LRC + Packet[i]; // add all bytes into LRC
For this example: LRC = 0x3F + 0x46 + 0x6C + 0x6F + 0x77 = 0x1D7 (if carries are not discarded)
LRC = 0xD7 discarding the carry LRC = -LRC // two’s complement
Two’s complement is ~(0xD7) + 1 = 0x28 + 1 = 0x29 (The ~ is the not operator) (see Wikipedia for more on not operator or two’s complement)
Now split the result into high and low bits, 2 and 9.
Convert each of these values to their ASCII hex equivalent.
2 -> 0x32
9 -> 0x39
Packet[5] = high 4 bits of LRC converted to ASCII, 2 -> 0x32
Packet[6] = low 4 bits of LRC converted to ASCII, 9 -> 0x39
Packet[7] = 0x0D // carriage return Packet[8]= 0x0A // line feed
Recap:
1) Add all bytes in message
2) Apply NOT to result and add 1 (2’s complement)
3) Split byte into high and low segments
4) Convert high and low segments to ASCII Hex value</packetlength;>
code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LabVIEWInterface
{
public class Calcbyte
{
public static byte[] CalcLRC(byte[] cmnd)
{
int i, j, bSize = cmnd.Length;
uint lrc, high, low, CR, LF;
string temp;
byte[] bytes = new byte[((bSize) + 4)];
lrc = 0x00;
CR = 0x0d;
LF = 0x0a;
//loop through input byte array
for (i = 0; i < cmnd.Length; i++)
{
//sum message bytes
lrc = lrc + (uint)cmnd[i];
//insert each message byte into result
bytes[i] = cmnd[i];
}
//remove remainder
if (lrc > 256)
{
lrc = lrc - (uint)(256 * Math.Floor((double)lrc / 256));
}
//perform 2's complement on sum
lrc = (ushort)(~lrc);
lrc = lrc + 1;
//remove remainder
if (lrc > 256)
{
lrc = lrc - (uint)(256 * Math.Floor((double)lrc / 256));
}
//split into high and low bits
temp = lrc.ToString("X");
high = (uint)temp[0];
low = (uint)temp[1];
//insert high, low, carriage return, and line feed into result
bytes[(bSize)] = (byte)high;
bytes[(bSize + 1)] = (byte)low;
bytes[(bSize + 2)] = (byte)CR;
bytes[(bSize + 3)] = (byte)LF;
//return result byte array with input, LRC, CR, LF
return bytes;
}
}
}
这篇关于cmnd =“?Flow"之间没有区别.和“！Flow"的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！