WriteFile() Function in VBA Excel not work correctly, it returns zero.

Question

Hello! i'm using the updated library for 64bits modCOMM - Written by: David M. Hitchner but i can't send data for serial port. The writefile() function returns zero all the time.

Below I copy the entry to the function. The readfile function is very similar, but it works fine. Please if anyone can help me I would appreciate it.

------------------- here the code-------------

Public Function CommWrite(intPortID As Integer, strData As String) As Long

Dim i As Integer
Dim lngStatus As Long, lngSize As Long
Dim lngWrSize As Long, lngWrStatus As Long

On Error GoTo Routine_Error

' Get the length of the data.
lngSize = Len(strData)

' Output the data.
lngWrStatus = WriteFile(udtPorts(intPortID).lngHandle, strData, lngSize, _
    lngWrSize, udtCommOverlap)

' Note that normally the following code will not execute because the driver
' caches write operations. Small I/O requests (up to several thousand bytes)
' will normally be accepted immediately and WriteFile will return true even
' though an overlapped operation was specified.

DoEvents

If lngWrStatus = 0 Then
    lngStatus = GetLastError

Answer 1

hEvent As LongPtr

Answer 2

Hi, Everyone

I am also Working on this modCOMM Code. I use this code to communicate with my weight scale. But can't figure out it which function or routine that i call on caommand button click Event.

----------------here is the code--------------

Option Compare Database

Private Sub Command157_Click()
    Dim intPortID As Integer ' Ex. 1, 2, 3, 4 for COM1 - COM4
    Dim lngStatus As Long
    Dim strError  As String
    Dim strData   As String


    ' Initialize Communications
    lngStatus = commopen(intPortID, "COM3" & CStr(intPortID), _
        "baud=9600 parity=N data=8 stop=1")
    If lngStatus <> 0 Then
    ' Handle error.
        lngStatus = CommGetError(strError)
    MsgBox "COM Error: " & strError
    End If
    

    ' Set modem control lines.
    lngStatus = CommSetLine(intPortID, LINE_RTS, True)
    lngStatus = CommSetLine(intPortID, LINE_DTR, True)

    ' Write data to serial port.
    lngSize = Len(strData)
    lngStatus = CommWrite(intPortID, strData)
    If lngStatus <> lngSize Then
    ' Handle error.
    End If



    ' Read maximum of 64 bytes from serial port.
    lngStatus = CommRead(intPortID, strData, 64)
    If lngStatus > 0 Then
        ' Process data.
    ElseIf lngStatus < 0 Then
        ' Handle error.
    End If

    ' Reset modem control lines.
    lngStatus = CommSetLine(intPortID, LINE_RTS, False)
    lngStatus = CommSetLine(intPortID, LINE_DTR, False)



    ' Close communications.
    Call CommClose(intPortID)
End Sub