Need help on ModbusTCPCom

[halosome]

Hello Archie,

Is there a doc or tutorials to explain how to use the functions and events of ModbusTCPCom?

I am able to read and write holding registers but still need to understand deeper and more. For example, are there signals indicating the status of ModbusTCPCom.read() / ModbusTCPCom.write(), like processing, finished, timeout, failed? Do I need to wait for one read/write finished before I start another read/write?

Thanks!

[Archie]

See if this helps any, this is common to all drivers:

https://advancedhmi.com/documentation/index.php?title=IComComponent

[halosome]

ase on that information, read/write should be always avoided.

I tried but I could not find the function beginreadmultiple/beginwritemultiple, they seems not included in ModBusTCPCOM.vb?

What would be the correct way to read or write 32 continuous integer? I tried beginread/beginwrite as below, but they don't seem to be the correct usage:

ModbusTCPCom.begineRead(40001.tostring, 32, arrayA as short())
FunctionHold200mS()
ModbusTCPCom.begineRead(40033.tostring, 32, arrayB as short())
FunctionHold200mS()
ModbusTCPCom.begineRead(40065.tostring, 32, arrayC as short())
FunctionHold200mS()

[Archie]

ModbusTCPCom1.BeginRead("40001",32)

[halosome]

do you have a whole code sample of the usage of ModbusTCPCom1.BeginRead("40001",32) and BeginWrite?

[Godra]

You can see some code here:

https://www.advancedhmi.com/forum/index.php?topic=1503.msg8027#msg8027

https://www.advancedhmi.com/forum/index.php?topic=1365.msg11532#msg11532

[halosome]

Thanks a lot! The code works.

[halosome]

Hello Godra,

Just some ideas on your code:
1) Data_received might need a watchdog for timeout;
2) BeginRead might need a try catch for communication broken;
3) Select case e.PlcAddress might be better, case "40001" ...

Thanks again.

[Godra]

Since you made suggestions then why not post your code as well, so other members can see it !?

[halosome]

I only wrote the select case but when I ran the program I realized the timeout and comm broken problems. Since you mentioned it, i just write a sample code for people who wants to have a look:


    Private Sub PLC_Read_Timer_Tick(sender As Object, e As EventArgs) Handles PLC_Read_Timer.Tick
         '100mS Timer

        PLC_Scan = IIf(PLC_Scan >= 9, 0, PLC_Scan + 1)

        Try

            Select Case PLC_IO_Scan
            Case 0
                 '
            Case 1
                ModbusTCPCom1.BeginRead("40001", 32)
            Case 2
                ModbusTCPCom1.BeginRead("43001", 32)
            Case 3
                ModbusTCPCom1.BeginRead("43101", 32)
            Case 4
                ModbusTCPCom1.BeginRead("40001", 32)
            Case 5
                ModbusTCPCom1.BeginRead("43001", 32)
            Case 6
                ModbusTCPCom1.BeginRead("43101", 32)
            Case 7
                ModbusTCPCom1.BeginRead("40001", 32)
            Case 8
                ModbusTCPCom1.BeginRead("43001", 32)
            Case 9
                ModbusTCPCom1.BeginRead("43101", 32)
            Case Else
                '
        End Select
        Catch ex As Exception
            ‘MessageBox.Show("Alarm: PLC Cannot be read!!")
        End Try

    End Sub

    Private Sub ModbusTCPCom1_DataReceived(sender As Object, e As Drivers.Common.PlcComEventArgs) Handles ModbusTCPCom1.DataReceived
        Dim ind As Integer = 0


Comm_WatchDog_Timer.Enabled = False

        Select Case e.PlcAddress
            Case "40001"
                ‘MessageBox.Show("PLC_Address = 40001”)
            Case "43101"
                For ind = 0 To 31
                    PC_Array(ind) = CInt(e.Values(ind))
                Next
            Case "43133"
                ‘MessageBox.Show("PLC_Address = 40001”)

            Case Else
                ‘MessageBox.Show("PLC_Error”)
        End Select

Comm_WatchDog_Timer.Enabled = True

    End Sub


    Private Sub Comm_WatchDog_Timer_Tick(sender As Object, e As EventArgs) Handles Comm_WatchDog_Timer.Tick
                      '5000mS Timer
                      ‘MessageBox.Show("Comm Timeout”)
    End Sub

[Godra]

Cool.