_send-basic-commands-in-visual-basic.md

title	layout	meta-description	share	author	about	cats	simple-description	date
Send Basic Commands in Visual Basic	text-width-sidebar	How to use the SerialPort class to send basic commands to the microbit	true	jez	How to open a send simple serial commands to the microbit.	visual basic	Advanced VB & microbit	2016-12-23 10:20:00 UTC

Introduction to VB

With the connection manager to the microbit written, it's very easy to send simple commands to the microbit.

In this example the microbit runs python (a blank program can be flashed). Visual Basic will send commands to the microbit:

• display.show(Image.HAPPY)
• display.show(Image.SAD)

Form Setup

Code

With the connection manager written and with the new form elements added there are only two things to do:

• Do something if btnHappy and btnSad are clicked
• Disable btnHappy and btnSad if not connected to the microbit.

Send Command on Click

If the btnHappy or btnSad send a python command to show the corresponding face on the microbit display.

{% highlight vb %} Private Sub btnHappy_Click(sender As Object, e As EventArgs) Handles btnHappy.Click port.WriteLine("display.show(Image.HAPPY)") End Sub

Private Sub btnSAD_Click(sender As Object, e As EventArgs) Handles btnSad.Click port.WriteLine("display.show(Image.SAD)") End Sub {% endhighlight %}

Disable btnHappy & btnSad

Dimming the buttons is simply a matter of updating the buttonState() function:

{% highlight vb %} Function buttonState() 'toggle buttons if connected If port.IsOpen Then btnConnect.Enabled = False btnDisconnect.Enabled = True cmbBox.Enabled = False btnScan.Enabled = False ' add new buttons btnHappy.Enabled = True btnSad.Enabled = True Else btnConnect.Enabled = True btnDisconnect.Enabled = False cmbBox.Enabled = True btnScan.Enabled = True ' add new buttons btnHappy.Enabled = False btnSad.Enabled = False End If End Function {% endhighlight %}

Final 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
        btnHappy.Enabled = True
        btnSad.Enabled = True
    Else
        btnConnect.Enabled = True
        btnDisconnect.Enabled = False
        cmbBox.Enabled = True
        btnScan.Enabled = True
        btnHappy.Enabled = False
        btnSad.Enabled = False
    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

Private Sub btnHappy_Click(sender As Object, e As EventArgs) Handles btnHappy.Click
    port.WriteLine("display.show(Image.HAPPY)")
End Sub

Private Sub btnSAD_Click(sender As Object, e As EventArgs) Handles btnSad.Click
    port.WriteLine("display.show(Image.SAD)")
End Sub

End Class{% endhighlight %}

Notes

• A better solution would be to use events to handle the dimming of buttons and boxes.