_connect-to-microbit-in-visual-basic.md

title	layout	meta-description	share	author	about	cats	simple-description	date
Connect to the Microbit in Visual Basic	text-width-sidebar	Connect to the microbit in Visual Basic with .NET Framework's SerialPort Class	true	jez	How to open a connection to the microbit in Visual Basic with .NET Framework's Serial Port Class.	visual basic	Basic VB & microbit	2016-12-23 10:20:00 UTC

Introduction to VB

Communicating with the microbit with VB is pretty straight-forward. This is the code that is reused throughout the howto section when connecting to the microbit.

This example uses Visual Studio Community Edition 2015 which is free. The code is a Visual Basic Windows Forms Application on .NET Framework .4.5.2.

Form Setup

Very (Very!) Basic Connection Manager

{% highlight vb %} Imports System.IO.Ports

Public Class Form1 Public Property PortName As String Dim WithEvents port As New SerialPort

Private Sub btnConnect_Click(sender As Object, e As EventArgs) Handles btnConnect.Click
    port.BaudRate = 115200
    port.PortName = cmbBox.SelectedItem.ToString
    port.Parity = Parity.None
    port.DataBits = 8
    port.StopBits = 1
    port.Open()
End Sub

Private Sub btnScan_Click(sender As Object, e As EventArgs) Handles btnScan.Click
    ' Show all available COM ports.
    For Each foundPort As String In My.Computer.Ports.SerialPortNames
        cmbBox.Items.Add(foundPort)
    Next
End Sub

Private Sub btnDisconnect_Click(sender As Object, e As EventArgs) Handles btnDisconnect.Click
    Try
        port.Close()
        Exit Sub
    Catch
        MessageBox.Show("Could Not Disconnect.")
    End Try
End Sub

End Class

{% endhighlight %}

Whilst this will happily connect to the microbit, there are a number of problems:

• Closing the application leaves the port open.
• Clicking 'Disconnect' without a connection raises an exception.
• Clicking 'Scan' populates cmbBox with items each time it's clicked.
• Clicking 'Connect' raises an exception if it cannot connect.

... and many others!

Fixing the code

{% highlight vb %} Imports System.IO.Ports

Public Class Form1 Public Property PortName As String Dim WithEvents port As New SerialPort

Function buttonState()
    'toggle buttons if connected
    If port.IsOpen Then
        btnConnect.Enabled = False
        btnDisconnect.Enabled = True
        cmbBox.Enabled = False
        btnScan.Enabled = False
    Else
        btnConnect.Enabled = True
        btnDisconnect.Enabled = False
        cmbBox.Enabled = True
        btnScan.Enabled = True
    End If

End Function

Private Sub btnConnect_Click(sender As Object, e As EventArgs) Handles btnConnect.Click
    ' Connect: open port and toggle button state.
    Try
        port.BaudRate = 115200
        port.PortName = cmbBox.SelectedItem.ToString
        port.Parity = Parity.None
        port.DataBits = 8
        port.StopBits = 1
        port.NewLine = vbCr ' EOL character to CR or \r in .WriteLine and .ReadLine
        port.Open()
        buttonState()

    Catch
        port.Close()
        MessageBox.Show("Could Not Connect. Is mu REPL open?")
    End Try
End Sub

Private Sub btnScan_Click(sender As Object, e As EventArgs) Handles btnScan.Click
    ' Scan: Populate cmbBox with found COM ports & Clear prev scans.
    cmbBox.Items.Clear()
    For Each sport As String In My.Computer.Ports.SerialPortNames
        cmbBox.Items.Add(sport)
    Next
    cmbBox.SelectedIndex = 0 ' select first COM port in cmbBox

End Sub

Private Sub btnDisconnect_Click(sender As Object, e As EventArgs) Handles btnDisconnect.Click
    ' Disconnect: Close ports & toggle button state.
    Try
        port.Close()
        buttonState()
        Exit Sub
    Catch
        MessageBox.Show("Could Not Disconnect.")
    End Try
End Sub

Private Sub Form1_FormClosing(sender As System.Object, e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing
    ' Close Application: Close serial port if open.
    If port.IsOpen() Then
        port.Close()
    End If
End Sub

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    buttonState()
End Sub

End Class {% endhighlight %}

Notes

• This code won't actually do anything apart from connect to the microbit.
• A better solution would be to use events to handle the dimming of buttons and boxes when connected.
• Adapted from waihung's blog & Martyn Currey's blog