关于CRC校验问题 (amobbs.com 阿莫电子技术论坛) -

yesful 发表于 2010-10-27 14:54:16

关于CRC校验问题

最近学习delphi写modbus协议串口通信，在CRC校验上遇到了问题，搞不是很明白。这是我参考网上资料写的一个程序，但校验结果与我想要的校验结果不一致。请大家帮我看一下什么原因，看一下我这校验方法是否正确。（多项式为CRC-16的）我在网上找了两个CRC校验工具，校验结果不一样的，不明白。
疑问：在RTU模式，单片机接收的指令串是8个16进制数，那我在上位机上，往单片机发送的是ASICC码，如何转换？如我想发送指令串‘010300010001+校验码’，是直接发送，还是用strtohex()转换成Hex？在数据CRC校验和发送的形式时，数据是以字符串形，还是以10进制，还是以16进制这个问题，很不清晰。
希望大家多多指教。
unit modbusread;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, CPortCtl, CPort;

type

TDataByte = array of byte;

TForm1 = class(TForm)
btnRead: TButton;
edAdress: TEdit;
edCRC: TEdit;
Label1: TLabel;
TXMemo: TMemo;
Label2: TLabel;
ComPort: TComPort;
ComLed1: TComLed;
ComLed2: TComLed;
ComLed3: TComLed;
Label3: TLabel;
Label4: TLabel;
Label5: TLabel;
btnSet: TButton;
RXMemo: TMemo;
Label6: TLabel;
Label7: TLabel;
Button2: TButton;
btnCom: TButton;
procedure btnSetClick(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure btnComClick(Sender: TObject);
procedure ComPortAfterOpen(Sender: TObject);
procedure ComPortAfterClose(Sender: TObject);
procedure btnReadClick(Sender: TObject);
procedure SendString(const Str : string);

private
{ Private declarations }
public
{ Public declarations }
end;

const
   CRCHi: array of byte =
(
$00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0, $80, $41, $00,
$C1, $81, $40, $01, $C0, $80, $41, $00, $C1, $81, $40, $00, $C1,
$81, $40, $01, $C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81,
$40, $00, $C1, $81, $40, $01, $C0, $80, $41, $00, $C1, $81, $40,
$01, $C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81, $40, $01,
$C0, $80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0,
$80, $41, $00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0, $80,
$41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41,
$01, $C0, $80, $41, $00, $C1, $81, $40, $01, $C0, $80, $41, $00,
$C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0,
$80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80,
$41, $00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0, $80, $41,
$00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41, $01,
$C0, $80, $41, $00, $C1, $81, $40, $01, $C0, $80, $41, $00, $C1,
$81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41, $00, $C1, $81,
$40, $01, $C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81, $40,
$01, $C0, $80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01,
$C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81, $40, $00, $C1,
$81, $40, $01, $C0, $80, $41, $00, $C1, $81, $40, $01, $C0, $80,
$41, $01, $C0, $80, $41, $00, $C1, $81, $40
) ;

CRCLo: array ofbyte =
(
$00, $C0, $C1, $01, $C3, $03, $02, $C2, $C6, $06, $07, $C7, $05,
$C5, $C4, $04, $CC, $0C, $0D, $CD, $0F, $CF, $CE, $0E, $0A, $CA,
$CB, $0B, $C9, $09, $08, $C8, $D8, $18, $19, $D9, $1B, $DB, $DA,
$1A, $1E, $DE, $DF, $1F, $DD, $1D, $1C, $DC, $14, $D4, $D5, $15,
$D7, $17, $16, $D6, $D2, $12, $13, $D3, $11, $D1, $D0, $10, $F0,
$30, $31, $F1, $33, $F3, $F2, $32, $36, $F6, $F7, $37, $F5, $35,
$34, $F4, $3C, $FC, $FD, $3D, $FF, $3F, $3E, $FE, $FA, $3A, $3B,
$FB, $39, $F9, $F8, $38, $28, $E8, $E9, $29, $EB, $2B, $2A, $EA,
$EE, $2E, $2F, $EF, $2D, $ED, $EC, $2C, $E4, $24, $25, $E5, $27,
$E7, $E6, $26, $22, $E2, $E3, $23, $E1, $21, $20, $E0, $A0, $60,
$61, $A1, $63, $A3, $A2, $62, $66, $A6, $A7, $67, $A5, $65, $64,
$A4, $6C, $AC, $AD, $6D, $AF, $6F, $6E, $AE, $AA, $6A, $6B, $AB,
$69, $A9, $A8, $68, $78, $B8, $B9, $79, $BB, $7B, $7A, $BA, $BE,
$7E, $7F, $BF, $7D, $BD, $BC, $7C, $B4, $74, $75, $B5, $77, $B7,
$B6, $76, $72, $B2, $B3, $73, $B1, $71, $70, $B0, $50, $90, $91,
$51, $93, $53, $52, $92, $96, $56, $57, $97, $55, $95, $94, $54,
$9C, $5C, $5D, $9D, $5F, $9F, $9E, $5E, $5A, $9A, $9B, $5B, $99,
$59, $58, $98, $88, $48, $49, $89, $4B, $8B, $8A, $4A, $4E, $8E,
$8F, $4F, $8D, $4D, $4C, $8C, $44, $84, $85, $45, $87, $47, $46,
$86, $82, $42, $43, $83, $41, $81, $80, $40
);

var
Form1: TForm1;

WriteComStr : string; //写命令字
ReadComStr : string; // 读命令字

{对象参数}
Address : string ;//对象地址

implementation

{$R *.dfm}

function crc16(var dataaddress :byte; datalength: byte): word;
var
   hi: byte;
   lo: byte;
   i: byte;
   index: byte;
   datadd: pbytearray;
begin
   hi := $FF;
   lo := $FF;
datadd := @dataaddress;
   i := 0;
   while (datalength > 0) do
   begin
   index := (hi xor datadd^);
   i := i + 1;
   hi := lo xor crchi;
   lo := crclo;
   datalength := datalength - 1;
   end;
   crc16 := hi shl 8 or lo;
end;

function ModBusCRC(Data: string): string; //生成modbus CRC数据
var
   CRC16Lo, CRC16Hi, CL, CH, UseHi, UseLo: Dword;
   i, index: integer;
begin
   CRC16Lo := $FF; //CRC16Lo为CRC寄存器低8位
   CRC16Hi := $FF; //CRC16Hi为CRC寄存器高8位
   CL := $01;
   CH := $A0; //A001 H 是CRC－16多项式代码
   for i := 1 to Length(Data) do
   begin
   CRC16Lo := CRC16Lo xor ord(Data); //每一个数据与CRC寄存器异或
   for index := 0 to 7 do
   begin
      UseHi := CRC16Hi;
      UseLo := CRC16Lo;
      CRC16Hi := CRC16Hi shr 1;
      CRC16Lo := CRC16Lo shr 1; //右移一位
      if ((UseHi and $1) = $1) then //如果高位字节最后一位是1的话
         CRC16Lo := CRC16Lo or $80; //低位字节右移后前面补1

      if ((UseLo and $1) = $1) then //如果LSB 为1，则与多项式进行异或
   begin
         CRC16Hi := CRC16Hi xor CH;
         CRC16Lo := CRC16Lo xor CL;
      end;
   end;
   end;

   Result := IntToHex(CRC16Lo, 2) + IntToHex(CRC16Hi, 2);
end;

function StrToHexStr(const S:string):string;
//字符串转换成16进制字符串
var
I:Integer;
begin
for I:=1 to Length(S) do
begin
if I=1 then
   Result:=IntToHex(Ord(S),2)
else Result:=Result+' '+IntToHex(Ord(S),2);
end;
end;

function HexStrToStr(const S:string):string;
//16进制字符串转换成字符串
var
t:Integer;
ts:string;
M,Code:Integer;
begin
t:=1;
Result:='';
while t<=Length(S) do
begin
while not (S in ['0'..'9','A'..'F','a'..'f']) do
   inc(t);
if (t+1>Length(S))or(not (S in ['0'..'9','A'..'F','a'..'f'])) then
   ts:='$'+S
else
   ts:='$'+S+S;
Val(ts,M,Code);
if Code=0 then
   Result:=Result+Chr(M);
inc(t,2);
end;
end;

procedure TForm1.btnSetClick(Sender: TObject);
begin
   ComPort.ShowSetupDialog;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
Form1.close;
end;

procedure TForm1.btnComClick(Sender: TObject);
begin
if ComPort.Connected then
   ComPort.close
   else ComPort.open;
end;

procedure TForm1.ComPortAfterOpen(Sender: TObject);
begin
btnCom.Caption:='stop';
// ShowStatus;
end;

procedure TForm1.ComPortAfterClose(Sender: TObject);
begin
btnCom.Caption:='open';
//ShowStatus;
end;

procedure TForm1.SendString(const Str : string);
var obj : PAsync;
begin
InitAsync(obj);
try
ComPort.WriteStrAsync(str,obj);
ComPort.WaitForAsync(obj);
// FTXNum := FTXNum + Length(Str);
finally
DoneAsync(obj);
// Timer1.Enabled := True;
// ShowTX;
end;
end;

procedure TForm1.btnReadClick(Sender: TObject);
var str : string;
   Data1 : TDataByte;
   c:word;
   i,l:integer;
begin
if not ComPort.Connectedthen
showmessage('please opten compot!')
else
begin
   ReadComStr := edAdress.text+'0300010001' ;
   Str := ReadComStr+ModBusCRC(ReadComStr);
   l := Length(ReadComStr);
      Setlength(Data1,l);
      for i:=0 to l-1 do
      Data1:= ord(ReadComStr);
      c:=CRC16(Data1,l);
   edCRC.text := inttohex(C,4);
   SendString(Str);
   TXMemo.Text := TXMemo.Text + Str+'';
end;
end;

end.

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关于CRC校验问题