Serial Port Interfacing in Microsoft Access

An example how to use the StrokeReader ActiveX to control a serial port from Microsoft Access.

How to Proceed

Download and install the ActiveX;
Open the VBA IDE and add a reference to the StrokeReader ActiveX control;
Paste the below code into a form module.

We intentionally do not place the ActiveX on a form. Instead, we dynamically create the object when the form is loading.

Anybody who wants to place the object on a form, be prepared to deal with Access bugs or manually connect to the port by setting Connected=True using a button or when the form is loading. Do not set the Connected=True in the ActiveX properties at the design time.

The Code Example

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Dim WithEvents sr As StrokeReader

Private Sub Form_Load()
  Set sr = CreateObject("STROKESCRIBE.StrokeReaderCtrl.1")

  sr.Port = 3  ' Specify your serial port number here
  sr.BaudRate = 9600
  sr.Parity = NOPARITY
  sr.DataBits = 8
  sr.StopBits = ONESTOPBIT
  sr.Connected = True
  
  If sr.Error Then
     Debug.Print sr.ErrorDescription
  End If
End Sub

Private Sub Form_UnLoad(Cancel As Integer)
   Set sr = Nothing  ' Destroys the serial port object when the form is unloading
End Sub

' The serial port event handler.
' The data reception process is asynchronous. You don't need to poll the port.
Private Sub sr_CommEvent(ByVal Evt As StrokeReaderLib.Event, ByVal data As Variant)
  Select Case Evt
    Case EVT_DISCONNECT
        Debug.Print "Disconnected"
    Case EVT_CONNECT
        Debug.Print "Connected"
    Case EVT_DATA
        buf = sr.Read(TEXT) ' Use BINARY to receive a byte array
        Debug.Print buf
  End Select
End Sub

Open the Immediate Window (press Ctrl+G in VBA) to see output of the Debug.Print statements.

Sending the Data

If you want to send data to to the remote device, use the following code:

Sub send()
  sr.Send "ABCD" ' A text string
End Sub

To send an array of bytes, use this code:

Sub send()
  Dim x(3) As Byte  'A byte array
  x(1) = 1
  x(2) = 2
  x(3) = 3
  sr.Send x
End Sub

Hardware Flow Control

If a serial device requires specific handshaking, use the following code to control the state of DTR/RTS lines:

sr.DTR = True
sr.RTS = True