Back in the days of Visual Basic 6.0, you had to use the MSComm Control that was shipped with VB6, the only problem with this method was you needed to make sure you included that control in your installation package, not really that big of a deal. The control did exactly what was needed for the task.
We were then introduced to .Net 1.1, VB programmers loved the fact that Visual Basic had finally evolved to an OO language. It was soon discovered that, with all it's OO abilities, the ability to communicate via a serial port wasn't available, so once again VB developers were forced to rely on the MSComm Control from previous versionsof Visual Basic, still not that big of a deal, but some were upset that an intrinsic way of serial port communication wasn't offered with the .net Framework.
Then along comes .Net 2.0, and this time Microsoft added the System.IO.Ports Namespace, and within that was the SerialPort Class. DotNet developers finally had an intrinsic way of serial port communication, without having to deal with the complexities of interoping with an old legacy ActiveX OCX control. One of the most useful methods in the SerialPort class is the GetPortNames Method. This allows you to retrieve a list of available ports (COM1,COM2,etc.) available for the computer the application is running on.
Now that we have that out of the way, lets move on to programming our application. As with all application I create, I keep functionality separated from presentation, I do this by creating Manager classes that manage the functionality or a given process. What we will be looking at is the code in my CommManager class. As with anything you write in .Net you need to add the references to the Namespace's you'll be using:
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1 Imports System
2 Imports System.Text
3 Imports System.Drawing
4 Imports System.IO.Ports
5 Imports System.Windows.Forms
In this application I wanted to give the user the option of what format they wanted to send the message in, either string or binary, so we have an enumeration for that, and an enumerations for the type of message i.e; Incoming, Outgoing, Error, etc. The main purpose of this enumeration is for changing the color of the text displayed to the user according to message type. Here are the enumerations:
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01 #Region "Manager Enums"
02 ''' <summary>
03 ''' enumeration to hold our transmission types
04 ''' </summary>
05 Public Enum TransmissionType
06 Text
07 Hex
08 End Enum
09
10 ''' <summary>
11 ''' enumeration to hold our message types
12 ''' </summary>
13 Public Enum MessageType
14 Incoming
15 Outgoing
16 Normal
17 Warning
18 [Error]
19 End Enum
20 #End Region
Next we have our variable list, 6 of them are for populating our class Properties, the others are being access throughout the manager class so they are made Global. Things are a bit different when sealing with delegates and how objects are access through VB.Net than they are in C#, so in the VB.Net version there are 2 more properties, and an extra Boolean variable used to determine if the buffer is to write the current data to the serial port. Here are the variables needed for the manager class:
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01 #Region "Manager Variables"
02 'property variables
03 Private _baudRate As String = String.Empty
04 Private _parity As String = String.Empty
05 Private _stopBits As String = String.Empty
06 Private _dataBits As String = String.Empty
07 Private _portName As String = String.Empty
08 Private _transType As TransmissionType
09 Private _displayWindow As RichTextBox
10 Private _msg As String
11 Private _type As MessageType
12 'global manager variables
13 Private MessageColor As Color() = {Color.Blue, Color.Green, Color.Black, Color.Orange, Color.Red}
14 Private comPort As New SerialPort()
15 Private write As Boolean = True
16 #End Region
NOTE:I always separate my code into sections using the #region ... #end region to make it easier when scanning my code. It is a design choice so it's not necessary if you don't want to do it.
Now we need to create our class properties. All the properties in this class are public read/write properties. As stated above we needed to add 2 additional properties for the conversion from C# to VB.Net. We have properties for the following items:
* Baud Rate: A measure of the speed of serial communication, roughly equivalent to bits per second.
* Parity: The even or odd quality of the number of 1's or 0's in a binary code, often used to determine the integrity of data especially after transmission.
* Stop Bits: A bit that signals the end of a transmission unit
* Data Bits: The number of bits used to represent one character of data.
* Port Name: The port with which we're communicating through, i.e; COM1, COM2, etc.
* MessageType: Outgoing, Incoming, Error, Warning, etc.
* Message: This is the actual message being sent through the serial port
We also have 4 properties that aren't related to the port itself, but with where the data will be displayed, what transmission type to use, the message type, and the message itself:
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01 ''' <summary>
02 ''' property to hold the StopBits
03 ''' of our manager class
04 ''' </summary>
05 Public Property StopBits() As String
06 Get
07 Return _stopBits
08 End Get
09 Set(ByVal value As String)
10 _stopBits = value
11 End Set
12 End Property
13
14 ''' <summary>
15 ''' property to hold the DataBits
16 ''' of our manager class
17 ''' </summary>
18 Public Property DataBits() As String
19 Get
20 Return _dataBits
21 End Get
22 Set(ByVal value As String)
23 _dataBits = value
24 End Set
25 End Property
26
27 ''' <summary>
28 ''' property to hold the PortName
29 ''' of our manager class
30 ''' </summary>
31 Public Property PortName() As String
32 Get
33 Return _portName
34 End Get
35 Set(ByVal value As String)
36 _portName = value
37 End Set
38 End Property
39
40 ''' <summary>
41 ''' property to hold our TransmissionType
42 ''' of our manager class
43 ''' </summary>
44 Public Property CurrentTransmissionType() As TransmissionType
45 Get
46 Return _transType
47 End Get
48 Set(ByVal value As TransmissionType)
49 _transType = value
50 End Set
51 End Property
52
53 ''' <summary>
54 ''' property to hold our display window
55 ''' value
56 ''' </summary>
57 Public Property DisplayWindow() As RichTextBox
58 Get
59 Return _displayWindow
60 End Get
61 Set(ByVal value As RichTextBox)
62 _displayWindow = value
63 End Set
64 End Property
65
66 ''' <summary>
67 ''' Property to hold the message being sent
68 ''' through the serial port
69 ''' </summary>
70 ''' <value></value>
71 ''' <returns></returns>
72 ''' <remarks></remarks>
73 Public Property Message() As String
74 Get
75 Return _msg
76 End Get
77 Set(ByVal value As String)
78 _msg = value
79 End Set
80 End Property
81
82 ''' <summary>
83 ''' Message to hold the transmission type
84 ''' </summary>
85 ''' <value></value>
86 ''' <returns></returns>
87 ''' <remarks></remarks>
88 Public Property Type() As MessageType
89 Get
90 Return _type
91 End Get
92 Set(ByVal value As MessageType)
93 _type = value
94 End Set
95 End Property
96 #End Region
To be able to instantiate any class object we create we need Constructors. Constructors are the entry point to your class, and is the first code executed when instantiating a class object. We have 2 constructors for our manager class, one that sets our properties to a specified value, and one that sets our properties to an empty value, thus initializing the variables preventing a NullReferenceException from occurring. We also add an EventHandler in the constructor, the event will be executed whenever there's data waiting in the buffer:
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01 #Region "Manager Properties"
02 ''' <summary>
03 ''' Property to hold the BaudRate
04 ''' of our manager class
05 ''' </summary>
06 Public Property BaudRate() As String
07 Get
08 Return _baudRate
09 End Get
10 Set(ByVal value As String)
11 _baudRate = value
12 End Set
13 End Property
14
15 ''' <summary>
16 ''' property to hold the Parity
17 ''' of our manager class
18 ''' </summary>
19 Public Property Parity() As String
20 Get
21 Return _parity
22 End Get
23 Set(ByVal value As String)
24 _parity = value
25 End Set
26 End Property
27
28 #Region "Manager Constructors"
29 ''' <summary>
30 ''' Constructor to set the properties of our Manager Class
31 ''' </summary>
32 ''' <param name="baud">Desired BaudRate</param>
33 ''' <param name="par">Desired Parity</param>
34 ''' <param name="sBits">Desired StopBits</param>
35 ''' <param name="dBits">Desired DataBits</param>
36 ''' <param name="name">Desired PortName</param>
37 Public Sub New(ByVal baud As String, ByVal par As String, ByVal sBits As String, ByVal dBits As String, ByVal name As
38
39 String, ByVal rtb As RichTextBox)
40 _baudRate = baud
41 _parity = par
42 _stopBits = sBits
43 _dataBits = dBits
44 _portName = name
45 _displayWindow = rtb
46 'now add an event handler
47 AddHandler comPort.DataReceived, AddressOf comPort_DataReceived
48 End Sub
49
50 ''' <summary>
51 ''' Comstructor to set the properties of our
52 ''' serial port communicator to nothing
53 ''' </summary>
54 Public Sub New()
55 _baudRate = String.Empty
56 _parity = String.Empty
57 _stopBits = String.Empty
58 _dataBits = String.Empty
59 _portName = "COM1"
60 _displayWindow = Nothing
61 'add event handler
62 AddHandler comPort.DataReceived, AddressOf comPort_DataReceived
63 End Sub
64 #End Region
The first think you need to know about serial port communication is writing data to the port. The first thing we do in our WriteData method is to check what transmission mode the user has selected, since binary data needs to be converted into binary, then back to string for displaying to the user. Next we need to make sure the port is open, for this we use the IsOpen Property of the SerialPort Class. If the port isnt open we open it by calling the Open Method of the SerialPort Class.
For writing to the port we use the Write Method. It is in this method we utilize the new boolean variable, write to determine if we want to write the data.This is used to handling byte transmission type when the data is in the incorrect format:
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01 #Region "WriteData"
02 Public Sub WriteData(ByVal msg As String)
03 Select Case CurrentTransmissionType
04 Case TransmissionType.Text
05 'first make sure the port is open
06 'if its not open then open it
07 If Not (comPort.IsOpen = True) Then
08 comPort.Open()
09 End If
10 'send the message to the port
11 comPort.Write(msg)
12 'display the message
13 _type = MessageType.Outgoing
14 _msg = msg + "" + Environment.NewLine + ""
15 DisplayData(_type, _msg)
16 Exit Select
17 Case TransmissionType.Hex
18 Try
19 'convert the message to byte array
20 Dim newMsg As Byte() = HexToByte(msg)
21 'Determine if we are goint
22 'to write the byte data to the screen
23 If Not write Then
24 DisplayData(_type, _msg)
25 Exit Sub
26 End If
27 'send the message to the port
28 comPort.Write(newMsg, 0, newMsg.Length)
29 'convert back to hex and display
30 _type = MessageType.Outgoing
31 _msg = ByteToHex(newMsg) + "" + Environment.NewLine + ""
32 DisplayData(_type, _msg)
33 Catch ex As FormatException
34 'display error message
35 _type = MessageType.Error
36 _msg = ex.Message + "" + Environment.NewLine + ""
37 DisplayData(_type, _msg)
38 Finally
39 _displaywindow.SelectAll()
40 End Try
41 Exit Select
42 Case Else
43 'first make sure the port is open
44 'if its not open then open it
45 If Not (comPort.IsOpen = True) Then
46 comPort.Open()
47 End If
48 'send the message to the port
49 comPort.Write(msg)
50 'display the message
51 _type = MessageType.Outgoing
52 _msg = msg + "" + Environment.NewLine + ""
53 DisplayData(MessageType.Outgoing, msg + "" + Environment.NewLine + "")
54 Exit Select
55 End Select
56 End Sub
57 #End Region
You will notice in this method we call three methods:
* HexToByte
* ByteToHex
* DisplayData
These methods are required for this manager. The HexToByte method converts the data provided to binary format, then the ByteToHex converts it back to hex format for displaying. The last one, DisplayData is where we marshal a call to the thread that created the control for displaying the data, since UI controls can only be accessed by the thread that created them. First we'll look at converting the string provided to binary format:
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01 #Region "HexToByte"
02 ''' <summary>
03 ''' method to convert hex string into a byte array
04 ''' </summary>
05 ''' <param name="msg">string to convert</param>
06 ''' <returns>a byte array</returns>
07 Private Function HexToByte(ByVal msg As String) As Byte()
08 'Here we added an extra check to ensure the data
09 'was the proper length for converting to byte
10 If msg.Length Mod 2 = 0 Then
11 'remove any spaces from the string
12 _msg = msg
13 _msg = msg.Replace(" ", "")
14 'create a byte array the length of the
15 'divided by 2 (Hex is 2 characters in length)
16 Dim comBuffer As Byte() = New Byte(_msg.Length / 2 - 1) {}
17 For i As Integer = 0 To _msg.Length - 1 Step 2
18 comBuffer(i / 2) = CByte(Convert.ToByte(_msg.Substring(i, 2), 16))
19 Next
20 write = True
21 'loop through the length of the provided string
22 'convert each set of 2 characters to a byte
23 'and add to the array
24 'return the array
25 Return comBuffer
26 Else
27 'Message wasnt the proper length
28 'So we set the display message
29 _msg = "Invalid format"
30 _type = MessageType.Error
31 ' DisplayData(_Type, _msg)
32 'Set our boolean value to false
33 write = False
34 Return Nothing
35 End If
36 End Function
37 #End Region
Here we convert the provided string to a byte array, then the WriteData method sends it out the port. For displaying we need to convert it back into string format, so we use the ByteToHex method we created:
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01 #Region "ByteToHex"
02 ''' <summary>
03 ''' method to convert a byte array into a hex string
04 ''' </summary>
05 ''' <param name="comByte">byte array to convert</param>
06 ''' <returns>a hex string</returns>
07 Private Function ByteToHex(ByVal comByte As Byte()) As String
08 'create a new StringBuilder object
09 Dim builder As New StringBuilder(comByte.Length * 3)
10 'loop through each byte in the array
11 For Each data As Byte In comByte
12 builder.Append(Convert.ToString(data, 16).PadLeft(2, "0"c).PadRight(3, " "c))
13 'convert the byte to a string and add to the stringbuilder
14 Next
15 'return the converted value
16 Return builder.ToString().ToUpper()
17 End Function
18 #End Region
The last method that WriteData depends on is the DisplayData method. Here we use the Invoke Method of our RichTextBox, the control used to display the data, to create a new EventHandler which creates a new Delegate for setting the properties we wish for our message, then appending it to the value already displayed.
We had to change the format of the DisplayData method as VB.Net handles delegates completely different than C#. Instead of putting the functionality of the delegate in the method, we had to create a seperate method, then use the AddressOf Method to reference the procedure that will act as our delegate:
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01 #Region "DisplayData"
02 ''' <summary>
03 ''' Method to display the data to and
04 ''' from the port on the screen
05 ''' </summary>
06 ''' <remarks></remarks>
07 <STAThread()> _
08 Private Sub DisplayData(ByVal type As MessageType, ByVal msg As String)
09 _displaywindow.Invoke(New EventHandler(AddressOf DoDisplay))
10 End Sub
11 #End Region
NOTE: You will notice that we have added the STAThreadAttribute to our method. This is used when a single thread apartment is required by a control, like the RichTextBox.
Now we will look at our delegate method, which is responsible for setting all of the properties of our display window,
which is a RichTextBox, as it has text formatting options not available to the regular TextBox:
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1 #Region "DoDisplay"
2 Private Sub DoDisplay(ByVal sender As Object, ByVal e As EventArgs)
3 _displaywindow.SelectedText = String.Empty
4 _displaywindow.SelectionFont = New Font(_displaywindow.SelectionFont, FontStyle.Bold)
5 _displaywindow.SelectionColor = MessageColor(CType(_type, Integer))
6 _displaywindow.AppendText(_msg)
7 _displaywindow.ScrollToCaret()
8 End Sub
9 #End Region
If you will read my tutorial on Serial Port Communication in C# you will see the same exact functionality that is in the DisplayData method, except in VB.Net, as pointed out earlier, requires the AddressOf Operator to reference a method to act as the delegate.The next method we will look at it used when we need to open the port initially. Here we set the BaudRate, Parity, StopBits, DataBits and PortName Properties of the SerialPort Class:
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01 #Region "OpenPort"
02 Public Function OpenPort() As Boolean
03 Try
04 'first check if the port is already open
05 'if its open then close it
06 If comPort.IsOpen = True Then
07 comPort.Close()
08 End If
09
10 'set the properties of our SerialPort Object
11 comPort.BaudRate = Integer.Parse(_baudRate)
12 'BaudRate
13 comPort.DataBits = Integer.Parse(_dataBits)
14 'DataBits
15 comPort.StopBits = DirectCast([Enum].Parse(GetType(StopBits), _stopBits), StopBits)
16 'StopBits
17 comPort.Parity = DirectCast([Enum].Parse(GetType(Parity), _parity), Parity)
18 'Parity
19 comPort.PortName = _portName
20 'PortName
21 'now open the port
22 comPort.Open()
23 'display message
24 _type = MessageType.Normal
25 _msg = "Port opened at " + DateTime.Now + "" + Environment.NewLine + ""
26 DisplayData(_type, _msg)
27 'return true
28 Return True
29 Catch ex As Exception
30 DisplayData(MessageType.[Error], ex.Message)
31 Return False
32 End Try
33 End Function
34 #End Region
Now that we have opened our port for communication for sending data through, we need to be able to close the port when we are finished without our application. Here we simply call the Close Method of the SerialPort Object, which also disposes of the internal stream being used for the data transmission:
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01 #Region " ClosePort "
02 Public Sub ClosePort()
03 If comPort.IsOpen Then
04 _msg = "Port closed at " + DateTime.Now + "" + Environment.NewLine + ""
05 _type = MessageType.Normal
06 DisplayData(_type, _msg)
07 comPort.Close()
08 End If
09 End Sub
10 #End Region
Next lets take a look at our event handler. This event will be executed whenever there's data waiting in the buffer. This method looks identical to our WriteData method, because it has to do the same exact work:
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01 #Region "comPort_DataReceived"
02 ''' <summary>
03 ''' method that will be called when theres data waiting in the buffer
04 ''' </summary>
05 ''' <param name="sender"></param>
06 ''' <param name="e"></param>
07 Private Sub comPort_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
08 'determine the mode the user selected (binary/string)
09 Select Case CurrentTransmissionType
10 Case TransmissionType.Text
11 'user chose string
12 'read data waiting in the buffer
13 Dim msg As String = comPort.ReadExisting()
14 'display the data to the user
15 _type = MessageType.Incoming
16 _msg = msg
17 DisplayData(MessageType.Incoming, msg + "" + Environment.NewLine + "")
18 Exit Select
19 Case TransmissionType.Hex
20 'user chose binary
21 'retrieve number of bytes in the buffer
22 Dim bytes As Integer = comPort.BytesToRead
23 'create a byte array to hold the awaiting data
24 Dim comBuffer As Byte() = New Byte(bytes - 1) {}
25 'read the data and store it
26 comPort.Read(comBuffer, 0, bytes)
27 'display the data to the user
28 _type = MessageType.Incoming
29 _msg = ByteToHex(comBuffer) + "" + Environment.NewLine + ""
30 DisplayData(MessageType.Incoming, ByteToHex(comBuffer) + "" + Environment.NewLine + "")
31 Exit Select
32 Case Else
33 'read data waiting in the buffer
34 Dim str As String = comPort.ReadExisting()
35 'display the data to the user
36 _type = MessageType.Incoming
37 _msg = str + "" + Environment.NewLine + ""
38 DisplayData(MessageType.Incoming, str + "" + Environment.NewLine + "")
39 Exit Select
40 End Select
41 End Sub
42 #End Region
We have 3 small methods left, and these are actually optional, for the lack of a better word. These mthods are used to populate my ComboBoxe's on my UI with the port names available on the computer, Parity values and Stop Bit values. The Parity and Stop Bits are available in enumerations included with the .Net Framework 2.0:
* Parity Enumeration
* StopBits Enumeration
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01 #Region "SetParityValues"
02 Public Sub SetParityValues(ByVal obj As Object)
03 For Each str As String In [Enum].GetNames(GetType(Parity))
04 DirectCast(obj, ComboBox).Items.Add(str)
05 Next
06 End Sub
07 #End Region
08
09 #Region "SetStopBitValues"
10 Public Sub SetStopBitValues(ByVal obj As Object)
11 For Each str As String In [Enum].GetNames(GetType(StopBits))
12 DirectCast(obj, ComboBox).Items.Add(str)
13 Next
14 End Sub
15 #End Region
16
17 #Region "SetPortNameValues"
18 Public Sub SetPortNameValues(ByVal obj As Object)
19
20 For Each str As String In SerialPort.GetPortNames()
21 DirectCast(obj, ComboBox).Items.Add(str)
22 Next
23 End Sub
24 #End Region
That is how you do Serial Port Communication in VB.Net. Microsoft finally gave us intrinsic tools to perform this task, no more relying on legacy objects. I am providing this class and a sample application to show how to implement what we just learned. What I am providing is under the GNU General Public License meaning you can modify and distribute how you see fit, but the license header must stay in tact. I hope you found this tutorial useful and informative, thatnk you for reading.
Happy Coding :)
~ Arun