Serial Port Communication in C# .

Welcome to our tutorial on Serial Port Communication in C#.Lately we've seen a lot of questions on how to send and receive data through a serial port, so weI 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 versions of 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.Worse yet,C# developers had to rely on a Visual Basic control and Namespace if they wanted to communicate via serial port.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 we create,we keep functionality separated from presentation,we do this by creating Manager classes that manage the functionality for a given process.What we will be looking at is the code in my CommunicationManager class.As with anything you write in .Net you need to add the references to the Namespace's you'll be using:

using System;
using System.Text;
using System.Drawing;
using System.IO.Ports;

In this application we 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:

#region Manager Enums
/// <summary>
/// enumeration to hold our transmission types
/// </summary>
public enum TransmissionType { Text, Hex }
/// <summary>
/// enumeration to hold our message types
/// </summary>
public enum MessageType { Incoming, Outgoing, Normal, Warning, Error };
#endregion

Next we have our variable list, 6 of them are for populating our class Properties, the other 2 are access throughout the class so they needed to be made global:

CODE

#region Manager Variables
//property variables
private string _baudRate = string.Empty;
private string _parity = string.Empty;
private string _stopBits = string.Empty;
private string _dataBits = string.Empty;
private string _portName = string.Empty;
private TransmissionType _transType;
private RichTextBox _displayWindow;
//global manager variables
private Color[] MessageColor = { Color.Blue,Color.Green, Color.Black, 
                                                  Color.Orange,Color.Red };
private SerialPort comPort = new SerialPort();
#endregion

Now we need to create our class properties. All the properties in this class are public read/write properties. We have properties for the following items of the Serial Port:

• 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.

We also have 2 properties that aren't related to the port itself, but with where the data will be displayed, and what transmission type to use:

#region Manager Properties
/// <summary>
/// Property to hold the BaudRate
/// of our manager class
/// </summary>
public string BaudRate
{
get { return _baudRate; }
set { _baudRate = value; }
}
/// <summary>
/// property to hold the Parity
/// of our manager class
/// </summary>
public string Parity
{
get { return _parity; }
set { _parity = value; }
/// <summary>
/// property to hold the StopBits
/// of our manager class
/// </summary>
public string StopBits
{
get { return _stopBits; }
set { _stopBits = value; }
}
/// <summary>
/// property to hold the DataBits
/// of our manager class
/// </summary>
public string DataBits
{
get { return _dataBits; }
set { _dataBits = value; }
}
/// <summary>
/// property to hold the PortName
/// of our manager class
/// </summary>
public string PortName
{
get { return _portName; }
set { _portName = value; }
}
/// <summary>
/// property to hold our TransmissionType
/// of our manager class
/// </summary>
public TransmissionType CurrentTransmissionType
{
get{ return _transType;}
set{ _transType = value;}
}
/// <summary>
/// property to hold our display window
/// value
/// </summary>
public RichTextBox DisplayWindow
{
get { return _displayWindow; }
set { _displayWindow = value; }
}
#endregion

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:

#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 CommunicationManager(string baud,string par,string sBits,
                                               string dBits, string name,RichTextBox rtb)
{
_baudRate = baud;
_parity = par;
_stopBits = sBits;
_dataBits = dBits;
_portName = name;
_displayWindow = rtb;
//now add an event handler
comPort.DataReceived += new SerialDataReceivedEventHandler(comPort_DataReceived);
}
/// <summary>
/// Comstructor to set the properties of our
/// serial port communicator to nothing
/// </summary>
public CommunicationManager()
{
_baudRate = string.Empty;
_parity = string.Empty;
_stopBits = string.Empty;
_dataBits = string.Empty;
_portName = "COM1";
_displayWindow = null;
//add event handler
comPort.DataReceived += new SerialDataReceivedEventHandler(comPort_DataReceived);
}
#endregion

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 isn't open we open it by calling the Open Method of the SerialPort Class. For writing to the port we use the Write Method:

#region WriteData
public void WriteData(string msg)
{
switch (CurrentTransmissionType)
{
case TransmissionType.Text:
//first make sure the port is open
//if its not open then open it
if (!(comPort.IsOpen == true)) comPort.Open();
//send the message to the port
comPort.Write(msg);
//display the message
DisplayData(MessageType.Outgoing, msg + "\n");
break;
case TransmissionType.Hex:
try
{
//convert the message to byte array
byte[] newMsg = HexToByte(msg);
//send the message to the port
comPort.Write(newMsg,0,newMsg.Length);
//convert back to hex and display
DisplayData(MessageType.Outgoing, ByteToHex(newMsg) + "\n");
}
catch (FormatException ex)
{
//display error message
DisplayData(MessageType.Error, ex.Message); }
finally
{
_displayWindow.SelectAll();
}
break;
default:
//first make sure the port is open
//if its not open then open it
if (!(comPort.IsOpen == true)) comPort.Open();
//send the message to the port
comPort.Write(msg);
//display the message
DisplayData(MessageType.Outgoing, msg + "\n");
break;
}
#endregion

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 byte[] HexToByte(string msg)
{
//remove any spaces from the string
msg = msg.Replace(" ", "");
//create a byte array the length of the
//string divided by 2
byte[] comBuffer = new byte[msg.Length / 2];
//loop through the length of the provided string
for (int i = 0; i < msg.Length; i += 2)
//convert each set of 2 characters to a byte
//and add to the array
comBuffer[i / 2] = (byte)Convert.ToByte(msg.Substring(i,2),16);
//return the array
return comBuffer;
}
#endregion

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 string ByteToHex(byte[] comByte)
{
//create a new StringBuilder object
{
StringBuilder builder = new StringBuilder(comByte.Length * 3);
//loop through each byte in the array
foreach (byte data in comByte)
//convert the byte to a string and add to the stringbuilder
builder.Append(Convert.ToString(data, 16).PadLeft(2, '0').PadRight(3, ' '));
//return the converted value
return builder.ToString().ToUpper();
}
#endregion

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:

#region DisplayData
/// <summary>
/// method to display the data to & from the port
// on the screen
/// </summary>
/// <param name="type">MessageType of the message</param>
/// <param name="msg">Message to display</param>
[STAThread]
private void DisplayData(MessageType type, string msg)
{
_displayWindow.Invoke(new EventHandler(delegate>
_displayWindow.SelectedText = string.Empty;
_displayWindow.SelectionFont= new Font(_displayWindow.SelectionFont, FontStyle.Bold);
displayWindow.SelectionColor = MessageColor[(int)type];
displayWindow.SelectionColor = MessageColor[(int)type];
displayWindow.AppendText(msg);
_displayWindow.ScrollToCaret();
}));
}
#endregion

You will notice that we hyave added the STAThread Attribute to our method. This is used when a single thread apartment is required by a control, like the RichTextBox.