Tag Archives: Visual Basic For Applications

How to Implement Modbus TCP Protocol using VBA with Excel

We will use Visual Basic for Applications (VBA) to communicate to a PLC using Modbus TCP protocol. Reading ten registers in the PLC and displaying a bar graph in Excel. Previously we have used VB6 to communicate Modbus TCP.
The following steps will be done:

  1. Explain Modbus TCP protocol
  2. Install OstroSoft Winsock Component
    – Winsock API Calls for communication on network
  3. Develop the Excel and VBA application
    (Microsoft Excel 2010)
  4. Communicate to the PLC and sample code
    (Do-More Simulator)

 

The Modbus TCP/IP or Modbus TCP is a Protocol  that is used for communications over TCP/IP networks. This is done on port 502. Modbus TCP does not require a checksum calculation as lower layers already provide checksum protection. You can think of this as a letter being sent and Ethernet TCP/IP acts like an envelope for the Modbus Commands. I will not go into the details of the communication protocol but here are some links to references:
Introduction to Modbus TCP/IP
Simply Modbus – Modbus TCP

 

OstroSoft Winsock Component
OSWINSCK.dll serves as a wrapper for the Winsock API and helps programmers to abstract from the complexity of API calls and focus on application functionality. Works with programming and scripting languages supporting COM.
You will need to download and install the OstroSoft Winsock Component on your computer.
For use with .NET, Visual Basic 4 or 5, Visual C++, ASP, VBA, VBScript, JavaScript or any other language, supporting COM:
1. Download oswinsck.exe
Modbus TCP using VBA Excel 001-min

2. Run downloaded file from Windows Explorer or command-line
Modbus TCP using VBA Excel 002-min
Hit OK
Modbus TCP using VBA Excel 003-min
I use the default directories where the program will be installed. Click the button to install.
Modbus TCP using VBA Excel 004-min
Leave the program group to the default so I know what the program is after installation. Click continue.
Modbus TCP using VBA Excel 005-min
Click OK
The OstroSoft Winsock Component is now installed.

Start Microsoft Excel.

Modbus TCP using VBA Excel 010-min
Select ‘Developer’ along the top tabs.
Modbus TCP using VBA Excel 020-min

If the Developer tab is not present then we must turn on the developer tab.
Select File | Options Modbus TCP using VBA Excel 021-minSelect ‘Customize Ribbon’Modbus TCP using VBA Excel 022-minCheck the ‘Developer’ under Main Tabs. Modbus TCP using VBA Excel 023-min

Under the Developer menu. Select ‘Visual Basic’
Modbus TCP using VBA Excel 030-minThe Visual Basic Editor window will now be displayed. Modbus TCP using VBA Excel 040-min
From the menu – Tools | References
We can now add the OstroSoft Winsock Component to our application.
Select OK
Modbus TCP using VBA Excel 050-minSelect Sheet1(Sheet1). Modbus TCP using VBA Excel 060-min

Now put the visual basic code in the Sheet1(Sheet1)
Here is the code:

‘This example uses OstroSoft Winsock Component
‘http://www.ostrosoft.com/oswinsck.asp

Option Explicit

Dim bytesTotal As Long
Dim sPage As String
Dim MbusQuery
Dim returnInfo
Dim wsTCPgdb
Dim WithEvents wsTCP As OSWINSCK.Winsock
Dim SetObject
Dim RetrieveData

Private Sub CommandButton1_Click() ‘ Retrieve Data
On Error GoTo ErrHandler
  Dim sServer As String
  Dim nPort As Long
  Dim StartTime
 
  DoEvents
  nPort = 502 ‘ See configuration in Do-More Designer
  ‘ Set the IP address of the PLC
  sServer = Sheets(“Sheet1”).Range(“B4″) ‘”192.168.1.3”
  RetrieveData = 1
  CommandButton1.BackColor = “&H0000FF00” ‘ Set colour to Green

‘Check to see if the object has been created. If not set wsTCP.
If SetObject = “” Then
Set wsTCP = CreateObject(“OSWINSCK.Winsock”)
wsTCP.Protocol = sckTCPProtocol
SetObject = 1
  End If

‘ Check the state of the TCP connection
‘0 sckClosed connection closed
‘1 sckOpen open
‘2 sckListening listening for incoming connections
‘3 sckConnectionPending connection pending
‘4 sckResolvingHost resolving remote host name
‘5 sckHostResolved remote host name successfully resolved
‘6 sckConnecting connecting to remote host
‘7 sckConnected connected to remote host
‘8 sckClosing Connection Is closing
‘9 sckError error occured

‘ If TCP is not connected, try to connect again.
If wsTCP.State <> 7 Then
    If (wsTCP.State <> sckClosed) Then
      wsTCP.CloseWinsock
    End If
    ‘ Open the connection
    wsTCP.Connect sServer, nPort
    StartTime = Timer ‘ Use the timer to determine if a connection cannot be made
    Do While ((Timer < StartTime + 2) And (wsTCP.State <> 7))
        DoEvents
    Loop
    If (wsTCP.State = 7) Then
    Else
       Exit Sub
    End If
End If

‘ If we are connected then request the information.
If (wsTCP.State = 7) Then
    MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(6) + Chr(0) + Chr(3) + Chr(0) + Chr(0) + Chr(0) + Chr(20)
    wsTCP.SendData MbusQuery ‘Send out the Modbus Information
    ‘ Read the information
    ‘0000:    Transaction Identifier
    ‘0000:    Protocol Identifier
    ‘0006:    Message Length (6 bytes to follow)
    ’00:      The Unit Identifier
    ’03:      The Function Code (read MHR Read Holding Registers)
    ‘0000:    The Data Address of the first register
    ‘0002:    The number of registers to write
   
    ‘ Write the information
    ‘0000:    Transaction Identifier
    ‘0000:    Protocol Identifier
    ‘0009:    Message Length (6 bytes to follow)
    ’01:      The Unit Identifier
    ’16:      The Function Code (read Analog Output Holding Registers)
    ‘0000:    The Data Address of the first register
    ‘0001:    The number of registers to write
    ’02:      The number of data bytes to follow
    ‘0030     The number to put into the register
   
    ‘ Note: Addresses are offset by 1
    ‘   Example: MHR1 = Address 0000
    ‘   Example: MHR30 = Address 0029
   
End If
  Exit Sub

ErrHandler:
  MsgBox “Error ” & Err.Number & “: ” & Err.Description
End Sub
Private Sub CommandButton2_Click() ‘ Stop the communication
RetrieveData = 0
CommandButton1.BackColor = “&H8000000F” ‘ Set the default colour
End Sub

Private Sub wsTCP_OnDataArrival(ByVal bytesTotal As Long)
  Dim sBuffer
  Dim i
  Dim MbusByteArray(500)
  Dim h As Integer
  Dim txtSource
wsTCP.GetData sBuffer
  txtSource = txtSource & sBuffer
 
Dim j As Byte
returnInfo = “”
For i = 1 To bytesTotal
    wsTCP.GetData j, vbByte
    MbusByteArray(i) = Asc(Mid(sBuffer, i, 2))
    returnInfo = returnInfo & Asc(Mid(sBuffer, i, 2))
Next
 txtSource = returnInfo
 txtSource = Val(Str((MbusByteArray(10) * 256) + MbusByteArray(11)))
 Sheets(“Sheet1”).Range(“B10”) = Val(Str((MbusByteArray(10) * 256) + MbusByteArray(11)))
 Sheets(“Sheet1”).Range(“B11”) = Val(Str((MbusByteArray(12) * 256) + MbusByteArray(13)))
 Sheets(“Sheet1”).Range(“B12”) = Val(Str((MbusByteArray(14) * 256) + MbusByteArray(15)))
 Sheets(“Sheet1”).Range(“B13”) = Val(Str((MbusByteArray(16) * 256) + MbusByteArray(17)))
 Sheets(“Sheet1”).Range(“B14”) = Val(Str((MbusByteArray(18) * 256) + MbusByteArray(19)))
 Sheets(“Sheet1”).Range(“B15”) = Val(Str((MbusByteArray(20) * 256) + MbusByteArray(21)))
 Sheets(“Sheet1”).Range(“B16”) = Val(Str((MbusByteArray(22) * 256) + MbusByteArray(23)))
 Sheets(“Sheet1”).Range(“B17”) = Val(Str((MbusByteArray(24) * 256) + MbusByteArray(25)))
 Sheets(“Sheet1”).Range(“B18”) = Val(Str((MbusByteArray(26) * 256) + MbusByteArray(27)))
 Sheets(“Sheet1”).Range(“B19”) = Val(Str((MbusByteArray(28) * 256) + MbusByteArray(29)))

DoEvents
‘ Determine if we retrieve the data again.
If RetrieveData = 1 Then
    Call CommandButton1_Click
End If
End Sub

Private Sub wsTCP_OnError(ByVal Number As Integer, Description As String, ByVal Scode As Long, ByVal Source As String, ByVal HelpFile As String, ByVal HelpContext As Long, CancelDisplay As Boolean)
  MsgBox Number & “: ” & Description
End Sub

Private Sub wsTCP_OnStatusChanged(ByVal Status As String)
  Debug.Print Status
End Sub

Note: The program utilizes the CHR and STR functions to convert the data from binary to ASCII and back.
The highest value of a byte of data is 256. This is why we have to multiply the highest significant byte with 256

Interface:
Go back to Sheet1 and we can now put on the worksheet what we would like to see.

Note the following:
IP Address = B4
MHR 1 to 10 values located at B10 to B19
‘Stop Data’ – CommandButton2
‘Retrieve Data’  – CommandButton1

Modbus TCP using VBA Excel 070-min

 

Communication to the PLC

Start the Do-More Designer software.
Under the Project Browser select ‘System Configuration’
Modbus TCP using VBA Excel 125-min
Make note of the IP address. If you are running the simulator then this is automatically filled in.
Modbus TCP using VBA Excel 126-min
Ensure that the Enable Modbus/TCP Server is checked. Also make sure that the TCP Port Number is 502.
Modbus TCP using VBA Excel 127-min

The sample PLC program will write values in the range from 0 to 4000. These values will be put in MHR 1 to MHR 10.

Here is the first couple of rungs of the PLC program. It will use clock bit flags to increment the MHR 1 channel. When it gets to the value above 4000, a move instruction will put a 0 back into MHR 1.
If input X0 turns on then the value in XW0 will be moved into MHR1 and the previous clock bit will not be in effect. Values will be between 0 and 4096. (12 bit resolution)
Modbus TCP using VBA Excel 150-min

This is repeated with different internal clock bit flags up to MHR10.

Running the program will produce the following:Modbus TCP using VBA Excel 120-min

As you can see the Modbus TCP protocol is easy to implement with visual basic for applications.
Download the PLC program and Excel file.

Additional Information:
Excel – Conditional Movement of Data

Watch on YouTube : How to Implement Modbus TCP Protocol using VBA with Excel
If you have any questions or need further information please contact me.
Thank you,
Garry



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.

To get this free article, subscribe to my free email newsletter.


Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.




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.)
Command Prompt

Type ‘regsvr32 netcomm.ocx’
RegSvr32

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

Now open Excel and make the following on Sheet 1.
Excel Omron Host Link 01

Select Developer and then Visual Basic. Excel Omron Host Link 02

If you do not have the Developer option to select, then do the following:
Select File : Options: Customized Ribbon
Excel Omron Host Link 03Select Developer and hit OK

Microsoft-VBA-Large

VBA – Visual Basic for Applications will open
Excel Omron Host Link 04

Insert a user form.
Excel Omron Host Link 05

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.
Excel Omron Host Link 06

Create three command buttons. This can be done by going to Design Mode,  and under the Insert menu you can select Command Buttons.Excel Omron Host Link 07

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"
Else
    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
Do
    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$, x * 4 + 4, 4)
        Next 'x
    End If
    DoEvents ' Do other tasks
    'Update the date and time
    Sheets("Sheet1").Range("C09") = Format(Date, "YYYY/MM/DD") + "    " + Format(Time, "HH:MM:SS")
Loop While startcycle = 1
If startcycle = 0 Then Exit Sub
communicate:
rxd$ = ""
Buffer = T$ + FCS$ + "*" + Chr$(13)
UserForm1.NETComm1.Output = Buffer
Time1 = Now
Timeout = Now + TimeValue("0:00:02")
Do
    If Timeout <= Time1 Then GoTo timeoutcom
    DoEvents
    Time1 = Now()
Loop Until UserForm1.NETComm1.InBufferCount >= charreturn
rxd$ = 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
GoSub FCS
If FCS <> fcs_rxd$ Then
    rxd$ = ""
End If
clearbuffer$ = UserForm1.NETComm1.InputData
Return
FCS:
    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$
Return
timeoutcom:
If startcycle = 0 Then Exit Sub
clearbuffer$ = UserForm1.NETComm1.InputData
rxd$ = ""
Return
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
Else
    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")
    Do
        If Len(StartADD) < 4 Then
            StartADD = "0" & StartADD
        End If
    Loop Until Len(StartADD) = 4
    NumWords = Sheets("Sheet1").Range("D7")
    Do
        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
Else
    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:
 Excel Omron Host Link 08

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’.
Security Warning

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.
VBA Warning

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,
Garry



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.

To get this free article, subscribe to my free email newsletter.


Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.