C# - Simple SerialPort singleton class

In my projects, some of them involves serial data communication. So, I think there is a desire for me to create a reusable class that I could always reuse whenever I develop any application that uses serial data communication protocol. Most likely when I work with the projects that is using Arduino board. Here is my singleton class called SerialPortManager which is basically based on System.IO.Ports.SerialPort class.

SerialPortManager.cs

This class source code also available on my Gist.

using System;
using System.IO;
using System.IO.Ports;
using System.Threading;

namespace HeiswayiNrird.Singleton
{
    public sealed class SerialPortManager
    {
        private static readonly Lazy<SerialPortManager> lazy = new Lazy<SerialPortManager>(() => new SerialPortManager());
        public static SerialPortManager Instance { get { return lazy.Value; } }

        private SerialPort _serialPort;
        private Thread _readThread;
        private volatile bool _keepReading;

        private SerialPortManager()
        {
            _serialPort = new SerialPort();
            _readThread = null;
            _keepReading = false;
        }

        /// <summary>
        /// Update the serial port status to the event subscriber
        /// </summary>
        public event EventHandler<string> OnStatusChanged;

        /// <summary>
        /// Update received data from the serial port to the event subscriber
        /// </summary>
        public event EventHandler<string> OnDataReceived;

        /// <summary>
        /// Update TRUE/FALSE for the serial port connection to the event subscriber
        /// </summary>
        public event EventHandler<bool> OnSerialPortOpened;

        /// <summary>
        /// Return TRUE if the serial port is currently connected
        /// </summary>
        public bool IsOpen { get { return _serialPort.IsOpen; } }

        /// <summary>
        /// Open the serial port connection using basic serial port settings
        /// </summary>
        /// <param name="portname">COM1 / COM3 / COM4 / etc.</param>
        /// <param name="baudrate">0 / 100 / 300 / 600 / 1200 / 2400 / 4800 / 9600 / 14400 / 19200 / 38400 / 56000 / 57600 / 115200 / 128000 / 256000</param>
        /// <param name="parity">None / Odd / Even / Mark / Space</param>
        /// <param name="databits">5 / 6 / 7 / 8</param>
        /// <param name="stopbits">None / One / Two / OnePointFive</param>
        /// <param name="handshake">None / XOnXOff / RequestToSend / RequestToSendXOnXOff</param>
        public void Open(
            string portname = "COM1",
            int baudrate = 9600,
            Parity parity = Parity.None,
            int databits = 8,
            StopBits stopbits = StopBits.One,
            Handshake handshake = Handshake.None)
        {
            Close();

            try
            {
                _serialPort.PortName = portname;
                _serialPort.BaudRate = baudrate;
                _serialPort.Parity = parity;
                _serialPort.DataBits = databits;
                _serialPort.StopBits = stopbits;
                _serialPort.Handshake = handshake;

                _serialPort.ReadTimeout = 50;
                _serialPort.WriteTimeout = 50;

                _serialPort.Open();
                StartReading();
            }
            catch (IOException)
            {
                if (OnStatusChanged != null)
                    OnStatusChanged(this, string.Format("{0} does not exist.", portname));
            }
            catch (UnauthorizedAccessException)
            {
                if (OnStatusChanged != null)
                    OnStatusChanged(this, string.Format("{0} already in use.", portname));
            }
            catch (Exception ex)
            {
                if (OnStatusChanged != null)
                    OnStatusChanged(this, "Error: " + ex.Message);
            }

            if (_serialPort.IsOpen)
            {
                string sb = StopBits.None.ToString().Substring(0, 1);
                switch (_serialPort.StopBits)
                {
                    case StopBits.One:
                        sb = "1"; break;
                    case StopBits.OnePointFive:
                        sb = "1.5"; break;
                    case StopBits.Two:
                        sb = "2"; break;
                    default:
                        break;
                }

                string p = _serialPort.Parity.ToString().Substring(0, 1);
                string hs = _serialPort.Handshake == Handshake.None ? "No Handshake" : _serialPort.Handshake.ToString();

                if (OnStatusChanged != null)
                    OnStatusChanged(this, string.Format(
                    "Connected to {0}: {1} bps, {2}{3}{4}, {5}.",
                    _serialPort.PortName,
                    _serialPort.BaudRate,
                    _serialPort.DataBits,
                    p,
                    sb,
                    hs));

                if (OnSerialPortOpened != null)
                    OnSerialPortOpened(this, true);
            }
            else
            {
                if (OnStatusChanged != null)
                    OnStatusChanged(this, string.Format(
                    "{0} already in use.",
                    portname));

                if (OnSerialPortOpened != null)
                    OnSerialPortOpened(this, false);
            }
        }

        /// <summary>
        /// Close the serial port connection
        /// </summary>
        public void Close()
        {
            StopReading();
            _serialPort.Close();

            if (OnStatusChanged != null)
                OnStatusChanged(this, "Connection closed.");

            if (OnSerialPortOpened != null)
                OnSerialPortOpened(this, false);
        }

        /// <summary>
        /// Send/write string to the serial port
        /// </summary>
        /// <param name="message"></param>
        public void SendString(string message)
        {
            if (_serialPort.IsOpen)
            {
                try
                {
                    _serialPort.Write(message);

                    if (OnStatusChanged != null)
                        OnStatusChanged(this, string.Format(
                        "Message sent: {0}",
                        message));
                }
                catch (Exception ex)
                {
                    if (OnStatusChanged != null)
                        OnStatusChanged(this, string.Format(
                            "Failed to send string: {0}",
                            ex.Message));
                }
            }
        }

        private void StartReading()
        {
            if (!_keepReading)
            {
                _keepReading = true;
                _readThread = new Thread(ReadPort);
                _readThread.Start();
            }
        }

        private void StopReading()
        {
            if (_keepReading)
            {
                _keepReading = false;
                _readThread.Join();
                _readThread = null;
            }
        }

        private void ReadPort()
        {
            while (_keepReading)
            {
                if (_serialPort.IsOpen)
                {
                    //byte[] readBuffer = new byte[_serialPort.ReadBufferSize + 1];
                    try
                    {
                        //int count = _serialPort.Read(readBuffer, 0, _serialPort.ReadBufferSize);
                        //string data = Encoding.ASCII.GetString(readBuffer, 0, count);
                        string data = _serialPort.ReadLine();

                        if (OnDataReceived != null)
                            OnDataReceived(this, data);
                    }
                    catch (TimeoutException) { }
                }
                else
                {
                    TimeSpan waitTime = new TimeSpan(0, 0, 0, 0, 50);
                    Thread.Sleep(waitTime);
                }
            }
        }
    }
}

Usage examples

To retrieve the data, just subscribe to OnDataReceived event.

Example:

using HeiswayiNrird.Singleton;
using System.Windows;

namespace SerialPortSingleton
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        // Constructor
        public MainWindow()
        {
            InitializeComponent();

            // Subscribe to the event
            SerialPortManager.Instance.OnDataReceived += Handler_OnDataReceived;
        }

        // Event handler
        private void Handler_OnDataReceived(object sender, string incomingData)
        {
            // TODO
            // Process the data from 'incomingData' variable...
        }
    }
}

For something simpler, you may use anonymous function and marshall it to the main UI thread.

Example:

using HeiswayiNrird.Singleton;
using System;
using System.Windows;

namespace SerialPortSingleton
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        // Constructor
        public MainWindow()
        {
            InitializeComponent();

            // Subscribe to the event
            SerialPortManager.Instance.OnDataReceived += (sender, incomingData) =>
            {
                // TODO
                // Process the data from 'incomingData' variable...
                double value = Convert.ToDouble(incomingData); // Assuming incomingData contains "123"

                // Update to UI...
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    BindingTextBoxValue = value;
                }));
            };
        }

        // Binding properties
        public double BindingTextBoxValue { get; set; }
    }
}

To handle opening or closing the serial port connection, you may just call Open() or Close() method.

Example:

// To open/start serial port on COM4 with 9600 bps
SerialPortManager.Instance.Open("COM4", 9600);

// To close/stop serial port on COM4
SerialPortManager.Instance.Close();

SerialPortManager also provides a public event to be subscribe for receiving any status update/response. To get the status message, just subscribe to OnStatusChanged event or OnSerialPortOpened event for getting boolean return either the serial port is opened or closed.

Example:

using HeiswayiNrird.Singleton;
using System.Windows;

namespace SerialPortSingleton
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        // Constructor
        public MainWindow()
        {
            InitializeComponent();

            // Subscribe to the event
            SerialPortManager.Instance.OnStatusChanged += (sender, status) =>
            {
                // Update connection status message to UI
                ConnectionStatus = status;
            };
        }

        // Binding properties
        public string ConnectionStatus { get; set; }
    }
}

Avoiding application hang during serial port closing

Don’t worry, this class doesn’t have the issue with that. Here is the design approach:

As you can see from the class source code, there is no System.IO.Ports.SerialPort.Close() is used as this will cause a deadlock issue or hang the application. This is because the serial port base stream is locked while serial port events are handled.

Instead, use ReadPort() method to be run on a new thread and use while loop statement for acquiring or reading data from the serial port. When SerialPortManager.Instance.Close() is called, _keepReading will be set to FALSE which will stop UI from receiving and updating the data while waiting the thread to fully terminate.