Visual Basic

Private Const NUM_VALUES As Integer = 10
Const INTEGER_SIZE As Integer = 4

Private m_TextBoxes() As TextBox

' Load saved values.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal _
    e As System.EventArgs) Handles MyBase.Load
    m_TextBoxes = New TextBox() {TextBox1, TextBox2, _
        TextBox3, TextBox4, TextBox5, TextBox6, TextBox7, _
        TextBox8, TextBox9, TextBox10}

    ' Get the file name.
    Dim file_name As String = GetFileName()

    ' See if the file exists.
    If System.IO.File.Exists(file_name) Then
        ' Open the file.
        Dim file_num As Integer = FreeFile()
        FileOpen(file_num, file_name, _
            OpenMode.Binary, OpenAccess.Read, _
            OpenShare.Shared, INTEGER_SIZE)

        ' Read the array.
        Dim integers(NUM_VALUES - 1) As Integer
        FileGet(file_num, integers)

        ' Close the file.
        FileClose(file_num)

        ' Display values.
        For i As Integer = 0 To NUM_VALUES - 1
            m_TextBoxes(i).Text = integers(i).ToString()
        Next i
    End If
End Sub

' Save the current values.
Private Sub Form1_FormClosing(ByVal sender As Object, ByVal _
    e As System.Windows.Forms.FormClosingEventArgs) Handles _
    Me.FormClosing
    ' Get the file name.
    Dim file_name As String = GetFileName()

    ' Create the file.
    Dim file_num As Integer = FreeFile()
    FileOpen(file_num, file_name, _
        OpenMode.Binary, OpenAccess.Write, _
        OpenShare.Shared, INTEGER_SIZE)

    ' Write the array.
    Dim integers(NUM_VALUES - 1) As Integer
    For i As Integer = 0 To NUM_VALUES - 1
        integers(i) = Val(m_TextBoxes(i).Text)
    Next i
    FilePut(file_num, integers)

    ' Close the file.
    FileClose(file_num)
End Sub

<DllImport("myCom.dll", CharSet:=CharSet.Unicode)> Public Function RFID_Comms(ByVal sTx As IntPtr, ByVal sRx As IntPtr, ByVal sRxSize As UShort, ByVal timeout As UShort) As Integer

<DllImport("myCom.dll", CharSet:=CharSet.Unicode)> Public Function RFID_Comms(ByVal sTx As IntPtr, ByVal sRx As IntPtr, ByVal sRxSize As UShort, ByVal timeout As UShort) As Integer
   End Function

sTx = Marshal.AllocHGlobal(100)
       sRx = Marshal.AllocHGlobal(300)
       sTx = StringToBSTR("RSD" & vbCr)
       result = RFID_Comms(sTx, sRx, 3000, 1000)
       lblOuput.Text = "Result: " & result
       txtBxOutput.Text = PtrToStringUni(sRx)

<DllImport("myCom.dll", CharSet:=CharSet.Unicode)> Function RFID_wGetVersion(ByVal s As IntPtr, ByVal size As UShort) As Integer
   End Function

Dim memString As String 
        Dim addrPTr As IntPtr = Marshal.AllocHGlobal(40) 
        res = RFIDP1_wGetVersion(addrPTr, 40)
        memString = PtrToStringUni(addrPTr)

        lblOuput.Text = "Result: " & res
        txtBxOutput.Text = memString
        lblOuput.Refresh()
        Marshal.FreeHGlobal(addrPTr)

Declare Function RFID_Comms Lib "myCom.dll" Alias "LibraryFunctionNameHere" (sTx As String, sRx As String, sRxSize As UShort, timeout As UShort)

Dave Kreskowiak wrote:

It's very strange to see Short integers being used where they are.

Public Declare Function RFIDP1_TagComms Lib "myCom.dll" Alias "RFIDP1_TagComms" (ByVal sTx As IntPtr, ByVal sRx As IntPtr, ByVal sRxSize As Integer, ByVal timeout As Integer) As Integer

tagRead = "SRD" 'various codes
Dim code() As Byte = System.Text.Encoding.ASCII.GetBytes(tagRead)
Dim codeLen As Integer = code.Length
'turn on rfid module!!!
result = PwrCtrl(1, True) 'targets separate PDA DLL
Threading.Thread.Sleep(500) 'allow power to stabilse
txtBxOutput.Text = "Module On"

Dim pointer As IntPtr = Marshal.AllocHGlobal(codeLen)
Marshal.Copy(code, 0, pointer, codeLen)
Dim sRx As IntPtr = Marshal.AllocHGlobal(127)
result = RFIDP1_TagComms(pointer, sRx, 127, 500)
If result = 0 Then
    lbltagResult.Text = "Tag Read"
Else
    lbltagResult.Text = result
End If
deCode(sRx)

Public Sub deCode(ByVal addr As IntPtr)
        'deCode the ascii code at the pointer
        Dim managedArray2(127) As Byte
        Marshal.Copy(addr, managedArray2, 0, 127)
        Dim enc As New System.Text.ASCIIEncoding() 'convert chars
        txtBxTN.Text = enc.GetString(managedArray2, 0, 18) 'to letters 
 End Sub