ModBus RTU,CRC,数据转换代码

 1 //======================================================================
 2 
 3 function ModBusCRC(Data: string): string; //生成modbus CRC数据
 4 var
 5   CRC16Lo, CRC16Hi, CL, CH, UseHi, UseLo: Dword;
 6   i, index: integer;
 7 begin
 8   CRC16Lo := $FF; //CRC16Lo为CRC寄存器低8位
 9   CRC16Hi := $FF; //CRC16Hi为CRC寄存器高8位
10   CL := $1;
11   CH := $A0; // A001 H 是CRC－16多项式代码
12   for i := 1 to Length(Data) do  begin
13     CRC16Lo := CRC16Lo xor ord(Data[i]); //每一个数据与CRC寄存器异或
14     for index := 0 to 7 do begin
15       UseHi := CRC16Hi;
16       UseLo := CRC16Lo;
17       CRC16Hi := CRC16Hi shr 1;
18       CRC16Lo := CRC16Lo shr 1; //右移一位
19       if ((UseHi and $1) = $1) then //如果高位字节最后一位是1的话
20         CRC16Lo := CRC16Lo or $80; //低位字节右移后前面补1
21 
22       if ((UseLo and $1) = $1) then begin//如果LSB 为1，则与多项式进行异或
23         CRC16Hi := CRC16Hi xor CH;
24         CRC16Lo := CRC16Lo xor CL;
25       end;
26     end;
27   end;
28 
29   Result := Char(CRC16Lo) + Char(CRC16Hi);
30 end;

 1 function  ModBusDataToSingle(st: string; var Value: Single): Boolean;
 2 var
 3   Pb: PByteArray;
 4 begin
 5   Result := False;
 6   if Length(st) &lt; 4 then
 7     Exit;
 8   Pb := PByteArray(@Value);
 9   Pb[3] := Ord(st[3]);
10   Pb[2] := Ord(st[4]);
11   Pb[1] := Ord(st[1]);
12   Pb[0] := Ord(st[2]);
13   Result := True;
14 end;
15 
16 function  ModBusDataToWord(st: string; var Value: Word): Boolean;
17 begin
18   Result := False;
19   if Length(st) &lt; 2 then
20     Exit;
21   Value := MakeWord(Ord(st[2]), Ord(st[1]));
22   Result := True;
23 end;