Machines without a serial port, virtual serial port software VSPD increase virtual serial port, compile environment VS2010 XP Sp3 (system), cut with API function to write a serial port on the vb.net application, createfile can open the serial port, but when settimeouts timeout error, refer to the great god ~ ~
Ps: I write serialport application can be normal use under the virtual serial port,
Procedure is As follows:

 Private Function Init_Com (ByVal ComNumber As String, ByVal Comsetting As String) As Boolean 
Try 
Dim ComSetup As DCB 
Dim Answer As COMSTAT 
Dim Start As COMSTAT 
Dim RetBytes As Long 
Dim retval As Long 
Dim CtimeOut As COMMTIMEOUTS 
Dim BarDCB As DCB 
Dim sa As SECURITY_ATTRIBUTES 

ComNum=CreateFile (ComNumber, & amp; HC0000000, 0, 0, & amp; H3, 0, 0) 
If - 1=ComNum Then 
MessageBox. Show (" port "& amp; ComNumber & amp; "Is invalid. Please correct Settings") 
Init_Com=False 
The Exit Function 
End the If 
'timeout 
CtimeOut. ReadIntervalTimeout=20 
CtimeOut. ReadTotalTimeoutConstant=1 
CtimeOut. ReadTotalTimeoutMultiplier=1 
CtimeOut. WriteTotalTimeoutConstant=10 
CtimeOut. WriteTotalTimeoutMultiplier=1 
Retval=SetCommTimeouts (ComNum CtimeOut) 'return 1, the wrong!!!!!!!!!!!!!! 
If retval=1 Then 
Retval=GetLastError () 
MessageBox. Show (" port timeouts is invalid "& amp; ComNumber & amp; "Error" & amp; Retval) 
Retval=CloseHandle (ComNum) 
Init_Com=False 
The Exit Function 
End the If 

Retval=BuildCommDCB (Comsetting BarDCB) 
If - 1=retval Then 
Retval=GetLastError () 
MessageBox. Show (" invalid device DCB piece "& amp; Comsetting & amp; "Error:" & amp; Retval) 
Retval=CloseHandle (ComNum) 
Init_Com=False 
The Exit Function 
End the If 

Retval=SetCommState (ComNum BarDCB) 
If - 1=retval Then 
Retval=GetLastError () 
MessageBox. Show (" invalid device DCB piece "& amp; Comsetting & amp; "Error" & amp; Retval) 
Retval=CloseHandle (ComNum) 
Init_Com=False 
The Exit Function 
End the If 
Catch the ex As Exception 
MessageBox. Show (ex. Message) 
End the Try 
End the Function 

CodePudding user response:

From the perspective of simplify code and design difficulty, or advise you, serial communication is realized by using MSComm control code is simple, and stable running, is the main idea of program design is to: to numerous to Jane

CodePudding user response:

If you must study the API, I give you an example of a VB6:
http://download.csdn.net/detail/veron_04/1339593

CodePudding user response:

 
//... 
If (hComm==INVALID_HANDLE_VALUE) {
HComm=0; 
Return FALSE; 
} 
//set to capture the event type 
SetCommMask (hComm EV_RXFLAG); 

//set the input and output buffer size 
SetupComm (hComm, 4096, 4096); 

//clear slow input/output impact area 
PurgeComm (hComm, PURGE_RXABORT | PURGE_RXCLEAR | PURGE_TXABORT | PURGE_TXCLEAR); 

//communication timeout parameter Settings 
COMMTIMEOUTS CommTimeOut; 
CommTimeOut. ReadIntervalTimeout=500;//set read timeout MAXDWORD 
CommTimeOut. ReadTotalTimeoutConstant=500; 
CommTimeOut. ReadTotalTimeoutMultiplier=500; 
CommTimeOut. WriteTotalTimeoutConstant=500; 
CommTimeOut. WriteTotalTimeoutMultiplier=100;//set to write timeout 
SetCommTimeouts (hComm, & amp; CommTimeOut);//set the timeout 
//...