Communication via Bluetooth virtual serial port does not work correctly.

Hi all,

I have tried to communicate with a bluetooth sensor device via a virtual serial port using UNITY3D in Windows7/8.1. However, the communication does not work correctly.

The virtual serial port outputs a wrong byte instead of a correct byte at every first, sometimes second, byte in a response packet.

The communication works perfectly in the same program compiled by Visual Studio 2013.

Here is a sample of the correct communication. If PC send a command byte "2e" , then the device respond ACK byte "ff", response ID "2f" and a byte sequence received by immedeiately using SerialPort.Write() and ReadByte() .

 WriteByte: 2e <--Command
 ReadByte:  ff 2f 01 00 00 00 06 00 <--Response

However, in UNITY 3D, the first byte, sometimes second too, of every response packet changes into "00".

 WriteByte: 2e <--Command
 ReadByte:  00 2f 01 00 00 00 06 00 <--Response
 
 WriteByte: 2e <--Command
 ReadByte:  00 00 01 00 00 00 06 00 <--Response

I will attach the sample code.

SerialHandler.cs

 using System;
 using System.Threading;
 using System.IO.Ports;
 using UnityEngine;
 
 public class SerialHandler
 {
     public String comPort;
     public System.IO.Ports.SerialPort serialPort = new System.IO.Ports.SerialPort();
     protected Thread readThread; 
 
     public SerialHandler(string comName)
     {
         comPort = comName;
         OpenConnection ();
     }
 
     public void WriteBytes(byte[] b, int index, int length)
     {
         foreach (byte wb in b)
         {
             Debug.Log("WriteBytes: " + wb.ToString("x2") + " Time: " + DateTime.Now.ToString("HH:mm:ss.ffff"));
         }
         serialPort.Write(b, index, length);
     }
 
     public void ReadByte()
     {
         while (serialPort.IsOpen) {
             try {
                 int b = serialPort.ReadByte ();
                 Debug.Log ("ReadByte: " + b.ToString ("x2") + " Time: " + DateTime.Now.ToString ("HH:mm:ss.ffff"));
             } catch(Exception e){
                 Debug.Log ("ReadByte Exception : " + e.Message + " Time: " + DateTime.Now.ToString ("HH:mm:ss.ffff"));
             }
         }
     }
 
     public void OpenConnection()
     {
             serialPort.BaudRate = 9600;
             serialPort.PortName = comPort;
             serialPort.ReadTimeout = 10000;
             serialPort.WriteTimeout = 10000;
 
             serialPort.Open();
 
             serialPort.DiscardInBuffer();
             serialPort.DiscardOutBuffer();
 
             System.Threading.Thread.Sleep (500);
             readThread = new Thread(ReadByte);
             readThread.Start ();
             System.Threading.Thread.Sleep (500);
     }
 
     public void CloseConnection()
     {
         serialPort.Close();
         System.Threading.Thread.Sleep (500);
         readThread.Abort ();
         System.Threading.Thread.Sleep (500);
         readThread = null;
         System.Threading.Thread.Sleep (500);
     }
 }

If someone encounterd the problem, please tell me a solution!

• OS: Windows7 32bit / Windows7 64bit / Windows8.1 64bit

• Device: Shimmer3 (www.shimmersensing.com)

• Bluetooth2.1+EDR

• UNITY v5.0.1p1 / 4.6.4p3

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