C# Serial Communication to Arduino

Question

I'm working on a project that involves my client software sending data to a Arduino microcontroller, AtMega32U4, through serial communication. I've looked through many answered questions so far yet none of them were specific to my problem. However, I believe my problem may be limited to threading issues or Arduino autoreset problems.

Code 1:

public MainForm()
    {
        InitializeComponent();
        serialPort1.DataReceived += new SerialDataReceivedEventHandler(serialPort1_DataReceived);
        serialPort1.DtrEnable = true;
        //serialPort1.RtsEnable = true;
    }
private void button3_Click(object sender, EventArgs e)
    {
        // Disables button while processing
        button3.Enabled = false;

        GetDir dir = new App.GetDir();
        dir.getCoords(Origin.Text, Destination.Text, Application.StartupPath + @"\temp2.html", "temp2.xml");
        dataBrowser.Navigate(Application.StartupPath + @"\temp2.html");
        dataBrowser.Update();

        waypoints = dir.coordsLat.Length;
        counter = dir.coordsLat.Length;
        coords = new double[dir.coordsLat.Length, 2];

        for (int i = 0; i < counter; i++)
        {
            coords[i, 0] = (Convert.ToDouble(dir.coordsLat[i]));
            coords[i, 1] = (Convert.ToDouble(dir.coordsLon[i]));
        }

        //serialPort1.Close();
        //System.Threading.Thread.Sleep(1000);


        if (serialPort1.IsOpen && !doubleClick)
        {
            serialPort1.Close();
            System.Threading.Thread.Sleep(2000);
            try
            {
                serialPort1.Open();
            }
            catch (Exception exception)
            {
                MessageBox.Show(exception.Message, "Cannot open serial port");
            }
            System.Threading.Thread.Sleep(2000);
        }
        else
        {
            if (!serialPort1.IsOpen)
            {
                try
                {
                    serialPort1.Open();
                    doubleClick = true;
                }
                catch (Exception exception)
                {
                    MessageBox.Show(exception.Message, "Cannot open serial port");
                }
                System.Threading.Thread.Sleep(2000);
                serialPort1.Write("^");
                System.Threading.Thread.Sleep(1000);
                Console.WriteLine('^');
                //button3.Enabled = true;
            }
        }  
    }

    private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        //System.Threading.Thread.Sleep(1000);
        readData = serialPort1.ReadLine();
        Console.WriteLine(readData);
        // If microcontroller sends "&", it is ready to receive next piece of data
        if (readData == "&")
        {
            sendRequest = true;
        }
        else
        {
            sendRequest = false;
        }

        // Write next piece of data to microcontroller if it is ready
        if (sendRequest)
        {
            this.BeginInvoke( new EventHandler (write_serialPort1));
        }
    }

In during the debugging of code 1, the event handler (serialPort1_DataReceived) never gets called. In this process, somehow button3_click gets called twice as the console outputs '^' twice. Afterwards, the client stalls since there is nothing beind received. Keep in mind that the Arduino will respond with an ampersand ('&') once it has received the circumflex ('^'). The Arduino code has been tested on the Arduino IDE and appears to be working fine. I believe the problem with button3_click being called twice comes from the button3_down and button3_up.

However, I was able to bypass this issue with Code 2. But also hit another brick wall.

Code 2 :

 private void button3_Click(object sender, EventArgs e)
    {
        // Disables button while processing
        button3.Enabled = false;

        GetDir dir = new App.GetDir();
        dir.getCoords(Origin.Text, Destination.Text, Application.StartupPath + @"\temp2.html", "temp2.xml");
        dataBrowser.Navigate(Application.StartupPath + @"\temp2.html");
        dataBrowser.Update();

        waypoints = dir.coordsLat.Length;
        counter = dir.coordsLat.Length;
        coords = new double[dir.coordsLat.Length, 2];

        for (int i = 0; i < counter; i++)
        {
            coords[i, 0] = (Convert.ToDouble(dir.coordsLat[i]));
            coords[i, 1] = (Convert.ToDouble(dir.coordsLon[i]));
        }

        serialPort1.Close();

        try
        {
            serialPort1.Open();
        }
        catch (Exception exception)
        {
            MessageBox.Show(exception.Message, "Cannot open serial port");
        }

        if (serialPort1.IsOpen)
        {
            System.Threading.Thread.Sleep(2000);
            using (serialPort1)
            {
                serialPort1.Write("^");
                System.Threading.Thread.Sleep(1000);
                Console.WriteLine("^");
                serialPort1.Close();
                System.Threading.Thread.Sleep(5000);
            }
        }
        else
        {
            button3.Enabled = true;
        }

    }

    private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        //SerialPort sp = (SerialPort)sender;

        System.Threading.Thread.Sleep(10000);
        /*if (!serialPort1.IsOpen)
        {
            serialPort1.Close();
            System.Threading.Thread.Sleep(10000);
            serialPort1.Open();
            System.Threading.Thread.Sleep(10000);
        }*/
        //serialPort1.Open();
        //using (sp)
        using (serialPort1)
        {
            serialPort1.Open();
            System.Threading.Thread.Sleep(5000);
            readData = serialPort1.ReadExisting();
            Console.WriteLine(readData);
            // If microcontroller sends "&", it is ready to receive next piece of data
            if (readData == "&")
            {
                sendRequest = true;
            }
            else
            {
                sendRequest = false;
            }

            // Write next piece of data to microcontroller if it is ready
            if (sendRequest)
            {
                this.BeginInvoke(new EventHandler(write_serialPort1));
            }
        }
    }

In Code 2, the event handler does get called and the button3_click only runs once. But when it tries to open the port, it returns the error 'Access to Port X denied'. Furthermore, I wish I didn't have to close and open the ports like this, but when the event handler is called (in an earlier code) it returned the error that the COM Port was not opened. In order to satisfy that error, I had to close it and reopen it during button3_click and event handling.

I've added a lot of delay in the code after I read about many problems dealing with the threading issues with serial communication. I had even tried a minute delay in hopes of a thread ending to solve the problem. However, no luck there.

I also specified my serial port in the MainForm designer instead of declaring it in the code (At first I did both and realized it was redundant). I'm not sure if this contributes to the problem, but I've seen examples of both being used.

Lastly, it could definitely deal with the Arduino auto resetting everytime a serial connection has been made (eg. opening and closing a port). In summary, it seems be sending data through serial, but unable to read the incoming data from serial.

Thank you for reading this and if someone could point me in the right direction, it would be very much appreciated.

Edit #1: Even after using BeginInvoke in Code 1, it still deadlocks because the event handler was never called.

Edit #2: Edits to Code 1 as per newbie's suggestions.

Edit #3: Added mainform initialization and updated Code 1 to current state.

Edit #4: Deleted (Commented out) the sleep at the event handler. I was sleeping during the event handler, thus I couldn't receive anything that the microcontroller would send to me. Code works fine as expected now.

Answer 1

In accordance to my 4th edit, deleted (Commented out) the sleep at the event handler. I was sleeping during the event handler, thus I couldn't receive anything that the microcontroller would send to me. Code works fine as expected now. Nothing was wrong with the serial ports on either components.

Answer 2

Make sure you are using COM1, if you do not COM1 serial port, change through Computer -> Device Manager -> Ports (COM & LPT) -> Select the COM to be changed -> Port Settings -> Advanced -> ComPort Number -> select COM1.

Make sure that you have installed jumper / connect with a screwdriver between pin2 and pin3 of COM1.

Add button1 and textBox1 to Form and run this program

using System;
using System.Windows.Forms;
using System.IO.Ports;
using System.Threading;
using System.Text;

namespace WindowsFormsApplication1 {
    public partial class Form1 : Form {

        const int MAX_BUFFER = 100;

        int i = 0;
        byte[] DataReceived = new byte[MAX_BUFFER];
        SerialPort serialPort = new SerialPort();

        public Form1() {
            InitializeComponent();
            serialPort.DataReceived += new SerialDataReceivedEventHandler(serialPort_DataReceived);
        }

        void serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e) {
            // wait data ready
            Thread.Sleep(500);

            // while data ready in buffer
            while (serialPort.IsOpen && serialPort.BytesToRead > 0) {
                // read data serial
                DataReceived[i] = Convert.ToByte(serialPort.ReadByte());

                // counter data
                i++;

                // reset conter if more then maxvalue
                if (i >= MAX_BUFFER) {
                    i = 0;
                }
            }

            if (i == 1 && DataReceived[0] == ASCIIEncoding.ASCII.GetBytes("^")[0]) {
                this.textBox1.Invoke(new Action(() => {
                    this.textBox1.Text = ASCIIEncoding.ASCII.GetString(DataReceived, 0, 1);

                }));
            }

        }

        public void InitSerialPort() {
            serialPort.PortName = "COM1";
            serialPort.BaudRate = 9600;
            serialPort.Parity = Parity.None;
            serialPort.DataBits = 8;
            serialPort.StopBits = StopBits.One;
            serialPort.ReceivedBytesThreshold = 1;
        }

        private void Form1_Load(object sender, EventArgs e) {
            // initialize serial port
            InitSerialPort();

            // assure port is closed before open it
            if (serialPort != null && serialPort.IsOpen) {
                serialPort.Close();
            }
            serialPort.Open();
        }

        private void button1_Click(object sender, EventArgs e) {
            if (serialPort.IsOpen) {
                serialPort.Write("^");
                // wait data sent
                Thread.Sleep(500);
            }
        }
    }
}