Welcome to my tutorial on Serial Port Communication in VB.Net. Lately Ive seen a lot of questions on how to send and receive data through a serial port, so I thought it was time to write on the topic. 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:
CODE
Imports System
Imports System.Text
Imports System.Drawing
Imports System.IO.Ports
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:
CODE
#Region "Manager Enums"
''' <summary>
''' enumeration to hold our transmission types
''' </summary>
Public Enum TransmissionType
Text
Hex
End Enum
''' <summary>
''' enumeration to hold our message types
''' </summary>
Public Enum MessageType
Incoming
Outgoing
Normal
Warning
[Error]
End Enum
#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:
CODE
#Region "Manager Variables"
'property variables
Private _baudRate As String = String.Empty
Private _parity As String = String.Empty
Private _stopBits As String = String.Empty
Private _dataBits As String = String.Empty
Private _portName As String = String.Empty
Private _transType As TransmissionType
Private _displayWindow As RichTextBox
Private _msg As String
Private _type As MessageType
'global manager variables
Private MessageColor As Color() = {Color.Blue, Color.Green, Color.Black, Color.Orange, Color.Red}
Private comPort As New SerialPort()
Private write As Boolean = True
#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:
CODE
''' <summary>
''' property to hold the StopBits
''' of our manager class
''' </summary>
Public Property StopBits() As String
Get
Return _stopBits
End Get
Set(ByVal value As String)
_stopBits = value
End Set
End Property
''' <summary>
''' property to hold the DataBits
''' of our manager class
''' </summary>
Public Property DataBits() As String
Get
Return _dataBits
End Get
Set(ByVal value As String)
_dataBits = value
End Set
End Property
''' <summary>
''' property to hold the PortName
''' of our manager class
''' </summary>
Public Property PortName() As String
Get
Return _portName
End Get
Set(ByVal value As String)
_portName = value
End Set
End Property
''' <summary>
''' property to hold our TransmissionType
''' of our manager class
''' </summary>
Public Property CurrentTransmissionType() As TransmissionType
Get
Return _transType
End Get
Set(ByVal value As TransmissionType)
_transType = value
End Set
End Property
''' <summary>
''' property to hold our display window
''' value
''' </summary>
Public Property DisplayWindow() As RichTextBox
Get
Return _displayWindow
End Get
Set(ByVal value As RichTextBox)
_displayWindow = value
End Set
End Property
''' <summary>
''' Property to hold the message being sent
''' through the serial port
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property Message() As String
Get
Return _msg
End Get
Set(ByVal value As String)
_msg = value
End Set
End Property
''' <summary>
''' Message to hold the transmission type
''' </summary>
''' <value></value>
''' <returns></returns>
''' <remarks></remarks>
Public Property Type() As MessageType
Get
Return _type
End Get
Set(ByVal value As MessageType)
_type = value
End Set
End Property
#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:
CODE
#Region "Manager Properties"
''' <summary>
''' Property to hold the BaudRate
''' of our manager class
''' </summary>
Public Property BaudRate() As String
Get
Return _baudRate
End Get
Set(ByVal value As String)
_baudRate = value
End Set
End Property
''' <summary>
''' property to hold the Parity
''' of our manager class
''' </summary>
Public Property Parity() As String
Get
Return _parity
End Get
Set(ByVal value As String)
_parity = value
End Set
End Property
#Region "Manager Constructors"
''' <summary>
''' Constructor to set the properties of our Manager Class
''' </summary>
''' <param name="baud">Desired BaudRate</param>
''' <param name="par">Desired Parity</param>
''' <param name="sBits">Desired StopBits</param>
''' <param name="dBits">Desired DataBits</param>
''' <param name="name">Desired PortName</param>
Public Sub New(ByVal baud As String, ByVal par As String, ByVal sBits As String, ByVal dBits As String, ByVal name As
String, ByVal rtb As RichTextBox)
_baudRate = baud
_parity = par
_stopBits = sBits
_dataBits = dBits
_portName = name
_displayWindow = rtb
'now add an event handler
AddHandler comPort.DataReceived, AddressOf comPort_DataReceived
End Sub
''' <summary>
''' Comstructor to set the properties of our
''' serial port communicator to nothing
''' </summary>
Public Sub New()
_baudRate = String.Empty
_parity = String.Empty
_stopBits = String.Empty
_dataBits = String.Empty
_portName = "COM1"
_displayWindow = Nothing
'add event handler
AddHandler comPort.DataReceived, AddressOf comPort_DataReceived
End Sub
#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:
CODE
#Region "WriteData"
Public Sub WriteData(ByVal msg As String)
Select Case CurrentTransmissionType
Case TransmissionType.Text
'first make sure the port is open
'if its not open then open it
If Not (comPort.IsOpen = True) Then
comPort.Open()
End If
'send the message to the port
comPort.Write(msg)
'display the message
_type = MessageType.Outgoing
_msg = msg + "" + Environment.NewLine + ""
DisplayData(_type, _msg)
Exit Select
Case TransmissionType.Hex
Try
'convert the message to byte array
Dim newMsg As Byte() = HexToByte(msg)
'Determine if we are goint
'to write the byte data to the screen
If Not write Then
DisplayData(_type, _msg)
Exit Sub
End If
'send the message to the port
comPort.Write(newMsg, 0, newMsg.Length)
'convert back to hex and display
_type = MessageType.Outgoing
_msg = ByteToHex(newMsg) + "" + Environment.NewLine + ""
DisplayData(_type, _msg)
Catch ex As FormatException
'display error message
_type = MessageType.Error
_msg = ex.Message + "" + Environment.NewLine + ""
DisplayData(_type, _msg)
Finally
_displayWindow.SelectAll()
End Try
Exit Select
Case Else
'first make sure the port is open
'if its not open then open it
If Not (comPort.IsOpen = True) Then
comPort.Open()
End If
'send the message to the port
comPort.Write(msg)
'display the message
_type = MessageType.Outgoing
_msg = msg + "" + Environment.NewLine + ""
DisplayData(MessageType.Outgoing, msg + "" + Environment.NewLine + "")
Exit Select
End Select
End Sub
#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:
CODE
#Region "HexToByte"
''' <summary>
''' method to convert hex string into a byte array
''' </summary>
''' <param name="msg">string to convert</param>
''' <returns>a byte array</returns>
Private Function HexToByte(ByVal msg As String) As Byte()
'Here we added an extra check to ensure the data
'was the proper length for converting to byte
If msg.Length Mod 2 = 0 Then
'remove any spaces from the string
_msg = msg
_msg = msg.Replace(" ", "")
'create a byte array the length of the
'divided by 2 (Hex is 2 characters in length)
Dim comBuffer As Byte() = New Byte(_msg.Length / 2 - 1) {}
For i As Integer = 0 To _msg.Length - 1 Step 2
comBuffer(i / 2) = CByte(Convert.ToByte(_msg.Substring(i, 2), 16))
Next
write = True
'loop through the length of the provided string
'convert each set of 2 characters to a byte
'and add to the array
'return the array
Return comBuffer
Else
'Message wasnt the proper length
'So we set the display message
_msg = "Invalid format"
_type = MessageType.Error
' DisplayData(_Type, _msg)
'Set our boolean value to false
write = False
Return Nothing
End If
End Function
#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:
CODE
#Region "ByteToHex"
''' <summary>
''' method to convert a byte array into a hex string
''' </summary>
''' <param name="comByte">byte array to convert</param>
''' <returns>a hex string</returns>
Private Function ByteToHex(ByVal comByte As Byte()) As String
'create a new StringBuilder object
Dim builder As New StringBuilder(comByte.Length * 3)
'loop through each byte in the array
For Each data As Byte In comByte
builder.Append(Convert.ToString(data, 16).PadLeft(2, "0"c).PadRight(3, " "c))
'convert the byte to a string and add to the stringbuilder
Next
'return the converted value
Return builder.ToString().ToUpper()
End Function
#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:
CODE
#Region "DisplayData"
''' <summary>
''' Method to display the data to and
''' from the port on the screen
''' </summary>
''' <remarks></remarks>
<STAThread()> _
Private Sub DisplayData(ByVal type As MessageType, ByVal msg As String)
_displayWindow.Invoke(New EventHandler(AddressOf DoDisplay))
End Sub
#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:
CODE
#Region "DoDisplay"
Private Sub DoDisplay(ByVal sender As Object, ByVal e As EventArgs)
_displayWindow.SelectedText = String.Empty
_displayWindow.SelectionFont = New Font(_displayWindow.SelectionFont, FontStyle.Bold)
_displayWindow.SelectionColor = MessageColor(CType(_type, Integer))
_displayWindow.AppendText(_msg)
_displayWindow.ScrollToCaret()
End Sub
#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:
CODE
#Region "OpenPort"
Public Function OpenPort() As Boolean
Try
'first check if the port is already open
'if its open then close it
If comPort.IsOpen = True Then
comPort.Close()
End If
'set the properties of our SerialPort Object
comPort.BaudRate = Integer.Parse(_baudRate)
'BaudRate
comPort.DataBits = Integer.Parse(_dataBits)
'DataBits
comPort.StopBits = DirectCast([Enum].Parse(GetType(StopBits), _stopBits), StopBits)
'StopBits
comPort.Parity = DirectCast([Enum].Parse(GetType(Parity), _parity), Parity)
'Parity
comPort.PortName = _portName
'PortName
'now open the port
comPort.Open()
'display message
_type = MessageType.Normal
_msg = "Port opened at " + DateTime.Now + "" + Environment.NewLine + ""
DisplayData(_type, _msg)
'return true
Return True
Catch ex As Exception
DisplayData(MessageType.[Error], ex.Message)
Return False
End Try
End Function
#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:
CODE
#Region " ClosePort "
Public Sub ClosePort()
If comPort.IsOpen Then
_msg = "Port closed at " + DateTime.Now + "" + Environment.NewLine + ""
_type = MessageType.Normal
DisplayData(_type, _msg)
comPort.Close()
End If
End Sub
#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:
CODE
#Region "comPort_DataReceived"
''' <summary>
''' method that will be called when theres data waiting in the buffer
''' </summary>
''' <param name="sender"></param>
''' <param name="e"></param>
Private Sub comPort_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
'determine the mode the user selected (binary/string)
Select Case CurrentTransmissionType
Case TransmissionType.Text
'user chose string
'read data waiting in the buffer
Dim msg As String = comPort.ReadExisting()
'display the data to the user
_type = MessageType.Incoming
_msg = msg
DisplayData(MessageType.Incoming, msg + "" + Environment.NewLine + "")
Exit Select
Case TransmissionType.Hex
'user chose binary
'retrieve number of bytes in the buffer
Dim bytes As Integer = comPort.BytesToRead
'create a byte array to hold the awaiting data
Dim comBuffer As Byte() = New Byte(bytes - 1) {}
'read the data and store it
comPort.Read(comBuffer, 0, bytes)
'display the data to the user
_type = MessageType.Incoming
_msg = ByteToHex(comBuffer) + "" + Environment.NewLine + ""
DisplayData(MessageType.Incoming, ByteToHex(comBuffer) + "" + Environment.NewLine + "")
Exit Select
Case Else
'read data waiting in the buffer
Dim str As String = comPort.ReadExisting()
'display the data to the user
_type = MessageType.Incoming
_msg = str + "" + Environment.NewLine + ""
DisplayData(MessageType.Incoming, str + "" + Environment.NewLine + "")
Exit Select
End Select
End Sub
#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:
CODE
#Region "SetParityValues"
Public Sub SetParityValues(ByVal obj As Object)
For Each str As String In [Enum].GetNames(GetType(Parity))
DirectCast(obj, ComboBox).Items.Add(str)
Next
End Sub
#End Region
#Region "SetStopBitValues"
Public Sub SetStopBitValues(ByVal obj As Object)
For Each str As String In [Enum].GetNames(GetType(StopBits))
DirectCast(obj, ComboBox).Items.Add(str)
Next
End Sub
#End Region
#Region "SetPortNameValues"
Public Sub SetPortNameValues(ByVal obj As Object)
For Each str As String In SerialPort.GetPortNames()
DirectCast(obj, ComboBox).Items.Add(str)
Next
End Sub
#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
SerialPortCommunication_VBNet.zip ( 223.7k )
Number of downloads: 4278This post has been edited by PsychoCoder: 13 Nov, 2007 - 06:21 AM
Serial Port Communication in VB.Net
13 Nov, 2007 - 06:10 AM
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