Servo Controller: Servo Control via .NET Application

Using the Serial Monitor in the Arduino IDE was convenient for quick testing, but ultimately I want a custom application to control all my servos. So my next step was to recreate the Serial Monitor as my own application (that I could eventually expand upon).

I created a very simple VB.NET application to communicate over a serial port. A couple notes on it:

- The program automatically connects to the first COM port it finds. That's generally pretty safe as nowadays the average computer user doesn't have any devices that communicate over a serial port. (Ahh, I remember back in the day, before USB, when you plugged the mouse into a COM port. Or Doom over serial, good times.) This automatic connection is dangerous if you do have devices such as 3-D printers that communicate over a COM port.
- The baud rate and similar are hard coded to match my Arduino code, but you may want to expose that as a configurable item.

The application in action:

The application in Visual Studio's designer:

The first dropdown list is for the COM port (automatically selected to the first found at startup). It is named ddlCOMPort.

The buttons from left to right are: btnConnect, btnDisconnect, btnRefreshPorts, btnClear, and btnSend.

The input text box is txtSend, and the output read-only text box is txtReceive.

The code:

Imports System.IO.Ports

Public Class FormMain

    ''' <summary>
    ''' Definite a delegate to transfer incoming data from the background
    ''' (serial) thread to the foreground (UI) thread.
    ''' </summary>
    ''' <param name="incomingBuffer"></param>
    ''' <remarks></remarks>
    Private Delegate Sub ProcessIncomingTextDelegate(ByVal incomingBuffer As String)

    ''' <summary>
    ''' The serial port object that will communicate.
    ''' </summary>
    ''' <remarks></remarks>
    Private WithEvents connectedSerialPort As New SerialPort()

    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.

    End Sub

    Private Sub FormMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Try
            refreshPortsList()

            If ddlCOMPort.SelectedIndex >= 0 Then
                ' Port is found, attempt to connect to it.
                connectSerialPort()
            Else
                ' Update which controls are enabled (so disconnect button is disabled at startup).
                updateConnectedEnableFields()
            End If
        Catch ex As Exception
        End Try
    End Sub

    Private Sub btnConnect_Click(sender As Object, e As EventArgs) Handles btnConnect.Click
        Try
            connectSerialPort()
        Catch ex As Exception
        End Try
    End Sub

    Private Sub btnDisconnect_Click(sender As Object, e As EventArgs) Handles btnDisconnect.Click
        Try
            disconnectSerialPort()
        Catch ex As Exception
        End Try
    End Sub

    Private Sub btnSend_Click(sender As Object, e As EventArgs) Handles btnSend.Click
        Try
            connectedSerialPort.Write(txtSend.Text + vbCrLf)
            txtSend.Text = ""
        Catch ex As Exception
        End Try
    End Sub

    Private Sub connectedSerialPort_DataReceived(sender As Object, e As SerialDataReceivedEventArgs) Handles connectedSerialPort.DataReceived
        Try
            ' Received data from the serial port, send it for processing.
            processIncomingData(connectedSerialPort.ReadExisting())
        Catch ex As Exception
        End Try
    End Sub

    Private Sub connectedSerialPort_ErrorReceived(sender As Object, e As SerialErrorReceivedEventArgs) Handles connectedSerialPort.ErrorReceived
        Try
        Catch ex As Exception
        End Try
    End Sub

    Private Sub btnRefreshPorts_Click(sender As Object, e As EventArgs) Handles btnRefreshPorts.Click
        Try
            refreshPortsList()
        Catch ex As Exception
        End Try
    End Sub

    Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
        Try
            txtReceive.Text = ""
        Catch ex As Exception
        End Try
    End Sub

    ''' <summary>
    ''' Returns if the serial port is currently connected.
    ''' </summary>
    ''' <value></value>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Private ReadOnly Property isSerialPortConnected
        Get
            Return connectedSerialPort.IsOpen()
        End Get
    End Property

    ''' <summary>
    ''' Update whether or not each UI control should be enabled based on
    ''' the connection state.
    ''' </summary>
    ''' <remarks></remarks>
    Private Sub updateConnectedEnableFields()
        Try
            Dim isConnected As Boolean = isSerialPortConnected
            btnConnect.Enabled = Not isConnected
            btnDisconnect.Enabled = isConnected
            ddlCOMPort.Enabled = Not isConnected
            btnRefreshPorts.Enabled = Not isConnected
            btnSend.Enabled = isConnected
        Catch ex As Exception
        End Try
    End Sub

    ''' <summary>
    ''' Connect to the selected serial port.
    ''' </summary>
    ''' <remarks></remarks>
    Private Sub connectSerialPort()
        Try
            If ddlCOMPort.SelectedIndex >= 0 Then
                connectedSerialPort.PortName = ddlCOMPort.SelectedItem
                connectedSerialPort.BaudRate = 9600

                connectedSerialPort.WriteTimeout = -1
                connectedSerialPort.ReadTimeout = -1

                connectedSerialPort.ReadBufferSize = 4096
                connectedSerialPort.WriteBufferSize = 2048

                connectedSerialPort.Parity = IO.Ports.Parity.None
                connectedSerialPort.StopBits = IO.Ports.StopBits.One
                connectedSerialPort.DataBits = 8
                connectedSerialPort.Open()
            End If
            updateConnectedEnableFields()
        Catch ex As Exception
        End Try
    End Sub

    ''' <summary>
    ''' Disconnect the serial port.
    ''' </summary>
    ''' <remarks></remarks>
    Private Sub disconnectSerialPort()
        Try
            connectedSerialPort.Close()
            updateConnectedEnableFields()
        Catch ex As Exception
        End Try
    End Sub

    ''' <summary>
    ''' Detect available serial ports and update the COM port list.
    ''' </summary>
    ''' <remarks></remarks>
    Private Sub refreshPortsList()
        Try
            ' Keep track of the selected port so we can reselect it after fresh.
            Dim currentlySelectedPort As String = ddlCOMPort.SelectedItem

            ' Get the available ports and update the dropdown list.
            Dim availablePorts As Array = IO.Ports.SerialPort.GetPortNames()
            ddlCOMPort.Items.Clear()
            ddlCOMPort.Items.AddRange(availablePorts)

            ' Reselect the previously selected port as a default.
            If currentlySelectedPort IsNot Nothing Then
                If ddlCOMPort.Items.Contains(currentlySelectedPort) Then
                    ddlCOMPort.SelectedItem = currentlySelectedPort
                End If
            End If

            If ddlCOMPort.SelectedIndex = -1 AndAlso ddlCOMPort.Items.Count > 0 Then
                ' No port selected but one is available, default to it.
                ddlCOMPort.SelectedIndex = 0
            End If
        Catch ex As Exception
        End Try
    End Sub

    ''' <summary>
    ''' Function to process incoming data from the serial port.
    ''' </summary>
    ''' <param name="incomingBuffer"></param>
    ''' <remarks></remarks>
    Private Sub processIncomingData(ByVal incomingBuffer As String)
        Try
            If txtReceive.InvokeRequired Then
                ' On background (serial port) thread. Invoke a delegate to call this
                ' function again on the foreground (UI) thread.
                Dim incomingTextDelegate As New ProcessIncomingTextDelegate(AddressOf processIncomingData)
                Me.Invoke(incomingTextDelegate, New Object() {incomingBuffer})
            Else
                ' On foreground (UI) thread. Process the message.
                txtReceive.Text += incomingBuffer
            End If
        Catch ex As Exception
        End Try
    End Sub
End Class

The code within this post is released into the public domain. You're free to use it however you wish, but it is provided "as-is" without warranty of any kind. In no event shall the author be liable for any claims or damages in connection with this software.