ModbusTCP : Unable to write to a register

[Slowpaddle]

This is my first post so forgive me if I mess this up.

I am using ModbusTCP to communicate with an Arduino via Ethernet using mudbus.h. (The correct spelling) I can read and write bit values and read register values without any issues. But for some reason I cannot write data to a register.

I would like to read a text file and send the values to two registers when the program starts. These values represent offset values for two TOF sensors connected to the Arduino.

I am hoping to be able to use them to line up my two Y Axis stepper motor positions on my CNC gantry and use the offsets to allow for any mounting errors.

Code: [Select]

Private Sub MainForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        If My.Computer.FileSystem.FileExists("C:\axis_offsets.txt") Then

            Dim reader As New System.IO.StreamReader("C:\axis_offsets.txt")

            Dim MyValue1, MyValue2 As String

            MyValue1 = reader.ReadLine()
            Dim CurrentValueInt1 As Integer = CInt(MyValue1)

            MyValue2 = reader.ReadLine()
            Dim CurrentValueInt2 As Integer = CInt(MyValue2)

            reader.Close()

            ModbusTCPCom1.Write("40003", CurrentValueInt1)
            ModbusTCPCom1.Write("40004", CurrentValueInt2)

        Else
            Dim writer As New System.IO.StreamWriter("C:\axis_offsets.txt", False)
            writer.WriteLine(0)
            writer.WriteLine(0)
            writer.Close()
        End If
    End Sub

This button click code will not work either.

Code: [Select]

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        ModbusTCPCom1.Write("40003", 2)
        ModbusTCPCom1.Write("40004", 2)
    End Sub

If I could figure out a way to use an ESP8266 with AHMI, I'd give it a go. Save me the problem of storing offsets on my computer and saving them on the ESP8266.

I'm a recently retired Industrial Electrician (Canada) so maybe I'm just getting old and missed something simple?

Thank you for any help one of you can provide. It would be deeply appreciated.

[Slowpaddle]

Just to add, I am using V3.99v if that helps.

Tried this as well to see if an error was thrown. Alas, nothing.

Code: [Select]

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Try
            ModbusTCPCom1.Write("40003", 2)
        Catch ex As Exception
            System.Windows.Forms.MessageBox.Show("Couldn't write to PLC. Error: " & ex.Message)
        End Try
    End Sub