How to Implement the Omron Host Link Protocol Part 2 – VBA

ACC Omron Host Link VBA

In Part 1, we used VB6 to communicate from the computer to the PLC. We will now use Visual Basic for Applications (VBA) to accomplish the same task. NETComm will be the serial driver and Excel will be the program that we will use. Using Excel we will have access to the Excel Object Model so we can utilize worksheets, ranges etc.

Please refer to Part 1 (How to Implement the Omron PLC Host Link Protocol) for the details of the wiring of the serial port and protocol sequence.

The first step in using VBA is to download and register NETComm.ocx. To use serial communications with VBA you must register the NETComm.ocx driver.

Download the NETComm.ocx file to the c:\ directory.

Call up a dos prompt with administrator authority. (Right click on the cmd.exe program and select run as administrator.)

Type ‘regsvr32 netcomm.ocx’

An information box will be shown indicating that the NETComm.ocx was registered successfully.

Now open Excel and make the following on Sheet 1.

Select Developer and then Visual Basic.

If you do not have the Developer option to select, then do the following:
Select File : Options: Customized Ribbon
Select Developer and hit OK

VBA – Visual Basic for Applications will open

Insert a user form.

Add NETComm1 to UserForm1. If it is not on your Toolbar, then select additional controls and select NETCommOCX.NETComm. Press the OK. Then drag this control onto your form.

Create three command buttons. This can be done by going to Design Mode,  and under the Insert menu you can select Command Buttons.

Here is the entire code for the application:

Private T$ ' Modual Scope for variable
Private TRead$
Private NumWords
Private startcycle
Private Sub CommandButton1_Click()
If NumWords = "" Then
    MsgBox "Set Read String"
    Exit Sub
End If
If startcycle = 0 Then
    startcycle = 1
    CommandButton1.BackColor = "&H0000FF00"
    startcycle = 0
    CommandButton1.BackColor = "&H8000000F"
    UserForm1.NETComm1.PortOpen = False ' Close Communication Port
    Exit Sub
End If
UserForm1.NETComm1.PortOpen = True ' Open Communication Port
Application.EnableEvents = True
    T$ = TRead$ ' Reset the Transmitted Information
    charreturn = 11 + (NumWords * 4) ' Determine the return characters
    GoSub FCS ' Checksum
    GoSub communicate ' Get informaiton
    'Check returned information and Display
    If Mid(rxd$, 6, 2) = "00" And (Len(rxd$)) >= charreturn Then
        For x = 1 To Sheets("Sheet1").Range("D7")
            Sheets("Sheet1").Range("B" & x + 10 - 1) = Mid(rxd$, x * 4 + 4, 4)
        Next 'x
    End If
    DoEvents ' Do other tasks
    'Update the date and time
    Sheets("Sheet1").Range("C09") = Format(Date, "YYYY/MM/DD") + "    " + Format(Time, "HH:MM:SS")
Loop While startcycle = 1
If startcycle = 0 Then Exit Sub
rxd$ = ""
Buffer = T$ + FCS$ + "*" + Chr$(13)
UserForm1.NETComm1.Output = Buffer
Time1 = Now
Timeout = Now + TimeValue("0:00:02")
    If Timeout <= Time1 Then GoTo timeoutcom
    Time1 = Now()
Loop Until UserForm1.NETComm1.InBufferCount >= charreturn
rxd$ = UserForm1.NETComm1.InputData
fcs_rxd$ = Left((Right(rxd$, 4)), 2)
If Left(rxd$, 1) = "@" Then
    T$ = Mid(rxd$, 1, (Len(rxd$) - 4))
ElseIf Mid(rxd$, 2, 1) = "@" Then
    T$ = Mid(rxd$, 2, (Len(rxd$) - 5))
    rxd$ = Mid(rxd$, 2, (Len(rxd$) - 1))
End If
If FCS <> fcs_rxd$ Then
    rxd$ = ""
End If
clearbuffer$ = UserForm1.NETComm1.InputData
    L = Len(T$)
    A = 0
    For J = 1 To L
        TJ$ = Mid$(T$, J, 1)
        A = Asc(TJ$) Xor A
    Next J
    FCS$ = Hex$(A)
    If Len(FCS$) = 1 Then FCS$ = "0" + FCS$
If startcycle = 0 Then Exit Sub
clearbuffer$ = UserForm1.NETComm1.InputData
rxd$ = ""
End Sub
Private Sub CommandButton2_Click()
If startcycle = 0 Then
    UserForm1.NETComm1.CommPort = Sheets("Sheet1").Range("A4")
    UserForm1.NETComm1.Settings = Sheets("Sheet1").Range("B4") & "," & Sheets("Sheet1").Range("C4") & "," & Sheets("Sheet1").Range("D4") & "," & Sheets("Sheet1").Range("E4")
    MsgBox UserForm1.NETComm1.Settings
    MsgBox "Stop Reading Parameters to Set MSComm"
End If
End Sub
Private Sub CommandButton3_Click()
If startcycle = 0 Then
    Unit = Sheets("Sheet1").Range("A7")
    If Len(Unit) < 2 Then Unit = "0" & Unit
    StartADD = Sheets("Sheet1").Range("C7")
        If Len(StartADD) < 4 Then
            StartADD = "0" & StartADD
        End If
    Loop Until Len(StartADD) = 4
    NumWords = Sheets("Sheet1").Range("D7")
        If Len(NumWords) < 4 Then
            NumWords = "0" & NumWords
        End If
    Loop Until Len(NumWords) = 4
    T$ = "@" & Unit & "RD" & StartADD & NumWords
    TRead$ = T$
    MsgBox T$
    For x = 1 To Sheets("Sheet1").Range("D7")
        Sheets("Sheet1").Range("A" & x + 10 - 1) = "DM " & Sheets("Sheet1").Range("C7") + x - 1
        Sheets("Sheet1").Range("B" & x + 10 - 1) = ""
    Next 'x
    For x = Sheets("Sheet1").Range("D7") To 200
        Sheets("Sheet1").Range("A" & x + 10) = ""
        Sheets("Sheet1").Range("B" & x + 10) = ""
    Next 'x
    MsgBox "Stop Reading Parameters to Set Read String"
End If
End Sub
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
End Sub

Note: The Chart on Sheet1 is just a selection of the first ten DM areas and insert a bar graph.

Running the program produces the following information:

Download the excel file ACC Omron Host Link VBA.XLS. This is the complete program mentioned above.


When you open the file it will warn you about macros. This is the VBA application. Press ‘Enable Macros’.

When changing the parameters on the screen, you will also get a warning about Active X. This is the NETComm.ocx which was registered above. Press ‘OK’ to run the application.

Additional Information:
Excel – Conditional Movement of Data

Watch on YouTube : How to Implement the Omron Host Link Protocol Part 2 – VBA
If you have any questions or need further information please contact me.
Thank you,

If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.

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2 thoughts on “How to Implement the Omron Host Link Protocol Part 2 – VBA”

  1. HI,

    I was looking around the website and came across this article “How to Implement the Omron PLC Host Link Protocol” and Garry you mentioned that you are able to give a copy of the program. Could I possible obtain this copy, as currently I’m working on a project and I having difficulties in getting a suitable VB example that would let send commands to Cable LC-RS9 RS232 9 pin for IBM PCXT for a weighting scale (SAG105 SAG105 mettler toledo ). Maybe this software is able to accomplish this. Unless you provide something that might be more related.

    Many thanks
    Satvir Singh

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