Arduino - Unity Serial Communication

Question

I am going to make a basic communication between Unity and Arduino. The problem that i have is that when i start sending data from unity to arduino, it's working properly. But when i start reading serial from Arduino. I got Access denied error !!!

After i read more about the issue, i can't find the real reason for that. I need to understand why something like that happens.

 using UnityEngine;
 using System.Collections;
 using System;
 using System.IO.Ports;
 using System.Text;
 using System.Threading;

 public class Program : MonoBehaviour {

public SerialPort mySerialPort = new SerialPort("COM7", 9600);
public volatile float speed=0;
volatile bool isPassed = true;
GameObject cube ;
public GUIStyle style ;
//  int readInterval = 4;
//  int alreadyCounter = 0;
//  string rxString = "";

void Start () {
    isPassed = true;
    speed = 0;
    //mySerialPort.ReadTimeout = 25;
    mySerialPort.Parity = Parity.None;
    mySerialPort.StopBits = StopBits.One;
    mySerialPort.DataBits = 8;
    mySerialPort.DtrEnable = true;

    cube = GameObject.FindGameObjectWithTag ("cube");

    /*foreach(string str in SerialPort.GetPortNames())
    {
        Debug.Log(string.Format("Existing COM port: {0}", str));
    };
    */
    try{
    mySerialPort.Open();
    }catch(Exception ex)
    {
        print("Start Error Opening : " + ex.ToString());
    }

    /*
new Thread (delegate() {
        updateSpeed();
    }).Start();
     */

}

void OnGUI(){
    GUI.Box (new Rect(100,100,100,100),"Speed : " + speed , style);
}
// Update is called once per frame
void Update () {
    cube.transform.Rotate(Vector3.up * speed *Time.deltaTime);
    if (mySerialPort.IsOpen) {
        speed = float.Parse (mySerialPort.ReadLine ()); 
    } else {
        if(mySerialPort!= null)
        {
            mySerialPort.Close();
            mySerialPort.Open();
        }
    }

        /*if (isPassed == true) {
        new Thread(delegate() {
            if(mySerialPort.IsOpen) {
                updateSpeed();
                isPassed = false;
            } else {
                try {
                    mySerialPort.Close();
                    mySerialPort.Open();
                } catch (Exception ex) {
                    print("Update Error Opening : " + ex.ToString());
                }
            }
        }).Start();
    }*/

}

public void updateSpeed()
{
    while (true) {
        speed = float.Parse(mySerialPort.ReadLine ());
        print ("Speed = " + speed);
        Thread.Sleep (60);
        mySerialPort.BaseStream.Flush ();
    }
}

void OnDestroy () 
{
    mySerialPort.Close();
}

}

Answer 1

Update:

Now, you can use Microsoft .net open source framework instead of the unity default, the serial communication works like a charm there.

Answer 2

When you call Close the SerialPort is disposed as you can read on the MSDN page. It also suggest to not try to reopen it immediately after closing it as it might not be closed yet.

Also since the SerialPort will be disposed you would have to create a new one. I would suggest to not closing and opening the port in Update when it's not open yet. Open it once in Start and just close it in OnDestroy.

edit
It seems you don't have to create a new SerialPort when you called Close on it. So it can be reused after "waiting some time".