如题,客户要在WINCC中实现MODBUS RTU 协议(做为从站)与一个远端的DCS进行通讯.我已经用了很多方法,可就是这样,在C脚本中用MSCOMM控件无法发送0字符,在VB中又无法发送大于128的字符.当然我更希望在C脚本中实现发送0字符,毕竟C脚本处理数据的功能要强很多.
最后的方法我就是使用API了!不过实在不希望使用API.

几经努力，这个问题应该算是可以得到解决了，呵呵。

对于字符串来说，C中的ASCII 0代表结束符，而VBS的CHR只支持到0~127，所以要解决这个问题，MsComm控件发送时必须使用Byte()格式的字节数组数据，接收也必须使用comInputModeBinary的接收方式。
不过遗憾的是VBS并不直接支持Byte()格式，其实我们声明的Dim SendByte(x)只是Variant()格式，因此需要想办法将其转换为Byte()格式就能拿来用了。
目前我的做法是用VB编写一个DLL文件，用于实现Variant()和Byte()之间的互相转化。
经测试，0~255的ASCII均可发送和接受，下面是效果图：




示例文件如下(WinCC V6.2 SP3)以及DLL文件（使用之前请选用RegSvr32.exe 注册一下）见附件：

点击此处查看附件

在全局C脚本中写一个全局动作,动作的触发条件是TAG触发,触发变量为"TrigComm"
#include "apdefap.h"

int gscAction( void )
{
typedef struct _COMMTIMEOUTS {
DWORD ReadIntervalTimeout; /* Maximum time between read chars. */
DWORD ReadTotalTimeoutMultiplier; /* Multiplier of characters. */
DWORD ReadTotalTimeoutConstant; /* Constant in milliseconds. */
DWORD WriteTotalTimeoutMultiplier; /* Multiplier of characters. */
DWORD WriteTotalTimeoutConstant; /* Constant in milliseconds. */
} COMMTIMEOUTS,*LPCOMMTIMEOUTS;
typedef struct _DCB {
DWORD DCBlength; /* sizeof(DCB) */
DWORD BaudRate; /* Baudrate at which running */
DWORD fBinary: 1; /* Binary Mode (skip EOF check) */
DWORD fParity: 1; /* Enable parity checking */
DWORD fOutxCtsFlow:1; /* CTS handshaking on output */
DWORD fOutxDsrFlow:1; /* DSR handshaking on output */
DWORD fDtrControl:2; /* DTR Flow control */
DWORD fDsrSensitivity:1; /* DSR Sensitivity */
DWORD fTXContinueOnXoff: 1; /* Continue TX when Xoff sent */
DWORD fOutX: 1; /* Enable output X-ON/X-OFF */
DWORD fInX: 1; /* Enable input X-ON/X-OFF */
DWORD fErrorChar: 1; /* Enable Err Replacement */
DWORD fNull: 1; /* Enable Null stripping */
DWORD fRtsControl:2; /* Rts Flow control */
DWORD fAbortOnError:1; /* Abort all reads and writes on Error */
DWORD fDummy2:17; /* Reserved */
WORD wReserved; /* Not currently used */
WORD XonLim; /* Transmit X-ON threshold */
WORD XoffLim; /* Transmit X-OFF threshold */
BYTE ByteSize; /* Number of bits/byte, 4-8 */
BYTE Parity; /* 0-4=None,Odd,Even,Mark,Space */
BYTE StopBits; /* 0,1,2 = 1, 1.5, 2 */
char XonChar; /* Tx and Rx X-ON character */
char XoffChar; /* Tx and Rx X-OFF character */
char ErrorChar; /* Error replacement char */
char EofChar; /* End of Input character */
char EvtChar; /* Received Event character */
WORD wReserved1; /* Fill for now. */
} DCB, *LPDCB;
#pragma code("kernel32.dll")
BOOL WriteFile( HANDLE hFile, LPCVOID lpBuffer,DWORD nNumberOfBytesToWrite,LPDWORD lpNumberOfBytesWritten, LPVOID lpOverlapped );
DWORD GetLastError(VOID);
VOID Sleep( DWORD dwMilliseconds );
BOOL CloseHandle(
HANDLE hObject
);
HANDLE CreateFileA(
LPCSTR lpFileName,
DWORD dwDesiredAccess,
DWORD dwShareMode,
LPSECURITY_ATTRIBUTES lpSecurityAttributes,
DWORD dwCreationDisposition,
DWORD dwFlagsAndAttributes,
HANDLE hTemplateFile
);
BOOL GetCommTimeouts( HANDLE hFile, LPCOMMTIMEOUTS lpCommTimeouts );
BOOL SetCommTimeouts(HANDLE hFile,LPCOMMTIMEOUTS lpCommTimeouts );
BOOL GetCommState( HANDLE hFile, LPDCB lpDCB );
BOOL SetCommState( HANDLE hFile, LPDCB lpDCB );
BOOL BuildCommDCBA(LPCSTR lpDef,LPDCB lpDCB );
#pragma code()

#define GetObjectA GetObject
int i;
union{ /*定义一个联合*/
float f1;
struct{ /*在联合中定义一个结构*/
char first;
char second;
char third;
char forth;
}half;
}data;

struct{
DWORD Internal;
DWORD InternalHigh;
DWORD Offset;
DWORD OffsetHigh;
LONG hEvent;
}ov1,*ov2;

char st1[100];
unsigned short crc;
DWORD n1;
HANDLE hFile;
COMMTIMEOUTS ctmoOld,ctmoNew;
DCB dcbCommPort;
__object *pdl = NULL;
__object *pic = NULL;
__object *obj = NULL;

if (GetTagBit("TrigComm")==0) return 0;
pdl = __object_create("PDLRuntime");
pic = pdl->GetPicture("MAIN");
obj = pic->GetObject("MScomm1");
data.f1=GetTagFloat("AA1");//获取数据
st1[0]=02;
st1[1]=03;
st1[2]=8;
st1[3]=data.half.first;
st1[4]=data.half.second;
st1[5]=data.half.third;
st1[6]=data.half.forth;
data.f1=GetTagFloat("AA2");
st1[7]=data.half.first;
st1[8]=data.half.second;
st1[9]=data.half.third;
st1[10]=data.half.forth;
crc=Calc_Crc((unsigned char *)st1,11);//计算CRC
st1[11]=crc & 0x00ff;
st1[12]=(crc & 0xff00)>>8;
obj->PortOpen=FALSE;
hFile = CreateFileA("COM3",0x80000000 0x40000000,0,NULL,3,0,NULL);
printf("HFILE=%d",hFile);
GetCommTimeouts(hFile,&ctmoOld);
ctmoNew.ReadTotalTimeoutConstant = 100;
ctmoNew.ReadTotalTimeoutMultiplier = 0;
ctmoNew.WriteTotalTimeoutMultiplier = 0;
ctmoNew.WriteTotalTimeoutConstant = 0;
SetCommTimeouts(hFile, &ctmoNew);
dcbCommPort.DCBlength = sizeof(DCB);
GetCommState(hFile, &dcbCommPort);
BuildCommDCBA("9600,N,8,1", &dcbCommPort);
SetCommState(hFile, &dcbCommPort);
WriteFile(hFile, st1,13, &n1, NULL);//通过串口发送数据
printf("n1=%d",n1);
Sleep(400);
CloseHandle(hFile);
obj->PortOpen=TRUE;
SetTagBit("TrigComm",FALSE);
__object_delete(obj);
__object_delete(pic);
__object_delete(pdl);
return 0;
最终显示效果如下:

在VBS脚本里变量都是以变体的形式存在的，但也还是有各种数据类型，只是有些是在VBS里无法构建的，比如Byte（）
接收可以按楼上“四书五经”的方法直接解析，为了方便，我也做了转换的函数

附件包含ＤＬＬ及ＶＢ源码和使用方法


点击此处查看附件