Help: Receiving a frame throug SerialPort

Question

I have a problem receiving a complet through the serial port. I have a device (Xbee) that is sending a frame which consists of 22 bytes. This frame is sent to the PC every 100ms at a baudrate of 4800bps.

I have made a class that uses asynchrone IO. When i use the class i create a instance and when i want to read the
newest value (frame) received i use "object.Temperatur" to get the string where the frame is stored. Temperatur is a string.

The big problem is to get a complete frame of 22 bytes stored in Temperatur (converted to HEX --> Temperatur = ConvertToHex(Encoding.ASCII.GetString(buffer, 0, bytesRead)); (ConvertToHex is a metod which i have defined in the class)). When i use this class i get only pieces and the pieces start from different bytes of the frame. Does anyone know what i could do to get a complete frame?

I have also shared my program. Feel free to take it if you can use something form it :)

I am sorry for my bad english.

////////////////////////////////////////////// MY CLASS //////////////////////////////////////////////////////
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.IO.Ports;
using System.Threading;
using System.Windows.Forms;

namespace ThermoCouple
{
    class AsynchIOThermo
    {
        SerialPort COMport = new SerialPort();

        private Stream inputStream;
        private AsyncCallback myCallBack;
        private byte[] buffer;
        private int BufferSize;

        public string Temperatur { set; get; }

        public AsynchIOThermo(string COMportName, int BaudRate, int DataBits, string Parity, string StopBits, int StreamBufferSize)
        {
            BufferSize = StreamBufferSize;


            COMport.ReadBufferSize = 2200;

            // Initial COMport
            COMport.PortName = COMportName;
            COMport.BaudRate = BaudRate;
            COMport.DataBits = DataBits;

            switch (Parity)
            {
                case "None":
                    COMport.Parity = System.IO.Ports.Parity.None;
                    break;
                case "Mark":
                    COMport.Parity = System.IO.Ports.Parity.Mark;
                    break;
                case "Even":
                    COMport.Parity = System.IO.Ports.Parity.Even;
                    break;
                case "Odd":
                    COMport.Parity = System.IO.Ports.Parity.Odd;
                    break;
                case "Space":
                    COMport.Parity = System.IO.Ports.Parity.Space;
                    break;
            }

            //StopBits Termo
            switch (StopBits)
            {
                case "1":
                    COMport.StopBits = System.IO.Ports.StopBits.One;
                    break;
                case "1.5":
                    COMport.StopBits = System.IO.Ports.StopBits.OnePointFive;
                    break;
                case "2":
                    COMport.StopBits = System.IO.Ports.StopBits.Two;
                    break;
            }

            COMport.Open();
            inputStream = COMport.BaseStream;
            buffer = new byte[StreamBufferSize];

            myCallBack = new AsyncCallback(OnCompletedRead);
        }

        /*abstract*/
        public void Run()
        {
            inputStream.BeginRead(
                buffer,
                0,
                buffer.Length,
                myCallBack,
                null);
        }


        public void OnCompletedRead(IAsyncResult asyncResult)
        {
            int bytesRead = inputStream.EndRead(asyncResult);

            if (bytesRead > 0)
            {
                Temperatur = ConvertToHex(Encoding.ASCII.GetString(buffer, 0, bytesRead));
                inputStream.BeginRead(buffer, 0, buffer.Length, myCallBack, null);
            }
        }

        private string ConvertToHex(string asciiString)
        {
            string hex = "";
            foreach (char c in asciiString)
            {
                int tmp = c;
                hex += String.Format("{0:x2}", (uint)System.Convert.ToUInt32(tmp.ToString()));
            }
            return hex;
        }

        public void Stop()
        {
            try
            {
                COMport.Close();
            }
            catch
            {
                MessageBox.Show("Unable to close the connection!");
            }
        }
    }
}

////////////////////////////////////////////// END OF CLASS /////////////////////////////////////////////////

Karthik Agarwal · Answer

Pretty good to hear that haris. Anyways I just forgot to say before Welcome to C-sharpcorner.

Karthik Agarwal · Answer

byte[] output_buffer = new byte[8];//EDITED int bytes_to_read = this.COMport.BytesToRead; this.COMport.Read(output_buffer 0 bytes_to_read); try doing it this way and let me know the result.

Sam Hobbs · Answer

Sleep is a bad solution. It is likely to stop working. There is nothing wrong with asynchronous I/O; it is more complicated to do but it has very valid uses and for serial I/O asynchronous I/O is a very good thing. I am very sorry I did not reply to this thread when I first saw it. My suggestion is to ensure that you are using flow control properly. Serial I/O uses two types of flow control; software and hardware. If the device at the other end uses one of the two then you must also use it. It is the only way to reliably keep both ends synchronized. I recommend that no one using serial I/O never use sleep! Never!

Haris · Answer

Yes!!!!! It works now. Sleep was the solution. Romba Nanri Sir

Karthik Agarwal · Answer

Do you mean that inserting sleep fetches more results than previous one's. If so try increasing the sleep time and check once if it fetches it's fine or else try playing with the sleep time (i.e try increasing and decreasing time) and check out the results.

Haris · Answer

I have put sleep like this and now i only receive ones. ////////////////////////////////////////// CODE ///////////////////////////////////////// public void OnCompletedRead(IAsyncResult asyncResult) { //int bytesRead = inputStream.EndRead(asyncResult); int bytes_to_read = this.COMport.BytesToRead; //if (bytesRead > 0) if (bytes_to_read > 0 ) { this.COMport.Read(output_buffer 0 bytes_to_read); Temperatur = ConvertToHex(Encoding.ASCII.GetString(output_buffer 0 bytes_to_read)); //Temperatur = ConvertToHex(Encoding.ASCII.GetString(buffer 0 bytesRead)); Thread.Sleep(100); inputStream.BeginRead(buffer 0 buffer.Length myCallBack null); } } /////////////////////////////////END /////////////////////////////////////////////// When i used the old metod (shown downunder) i get continuesly data recived but i do not get the whole frame. I get: Wanted frame: 7E 00 12 92 00 13 A2 00 40 71 03 75 A1 AB 01 01 00 00 01 00 24 1C Received frame: 00 12 92 00 13 A2 00 40 71 03 75 A1 AB 01 01 00 00 01 00 24 1C 7E 00 12 92 00 13 A2 00 40 71 03 75 A1 AB 01 01 00 00 01 00 24 1C 7E 00 12 92 00 13 A2 00 40 71 03 75 A1 AB 01 01 00 00 01 00 24 1C 7E 00 12 92 00 13 A2 00 40 71 03 75 A1 AB 01 01 00 00 01 00 24 1C 7E 00 12 92 00 13 A2 00 40 71 03 75 A1 AB 01 01 00 00 01 00 24 1C 7E ........ So I get the start byte separaterd now. //////////////////////////////////////CODE ////////////////////////////////////////// public void OnCompletedRead(IAsyncResult asyncResult) { int bytesRead = inputStream.EndRead(asyncResult); //int bytes_to_read = this.COMport.BytesToRead; if (bytesRead > 0) // if (bytes_to_read > 0 ) { // this.COMport.Read(output_buffer 0 bytes_to_read); //Temperatur = ConvertToHex(Encoding.ASCII.GetString(output_buffer 0 bytes_to_read)); Temperatur = ConvertToHex(Encoding.ASCII.GetString(buffer 0 bytesRead)); Thread.Sleep(50); inputStream.BeginRead(buffer 0 buffer.Length myCallBack null); } } ////////////////////////////////// END ////////////////////////////////////////

Karthik Agarwal · Answer

I was thinking on this from the time you said about your data speed and time. try introducing sleep for time so that serial port may get some time to read the data. I think data is flushing into the port which is causing problem. try writing sleep(1000); // here 1000 says 1000ms which is nothing but 1 sec. after every read cycle which may give some time for the port to read data. If that works fine then try reducing the time from 1000 to 500 and so on and settle down with the minimum time frame at which data is received perfectly. After trying this let me know the result.

Haris · Answer

The improvement is that i now receive a string which almost has the right length of a hole frame. But still the reading is uncontroled (Reading different places in a frame and therefor getting parts of frame). I also get a new error which is the amount of time a receive frames. After receving 2-3 times the program stops receiving but i can se that the port is still open and that data is flowing in (I see that on a LED that is implementet in my hardware). I have tested my hardware using docklight and it works (frame every 100ms). I realy appreciate your help.

Karthik Agarwal · Answer

That's good to hear from you if there are improvements how could you find those. If you can say what are those improvements probably i can work more and will get to know where to work. But it takes some time for me to come with a solution provided you give me more inputs.

Haris · Answer

I have configurated my program with the corrections you came with and i can se a bit improvement but I still have problems receiving a frame. I have uploaded my project with your corrections in a zip file. It is written in Visual Studio 2010. I have build a wireless temperaturesensor with two wireless modules (Xbee's) and i want the program to show the temperatur. It is nesessery that i run asynchronous IO because i will build more sensors later on and connect them. The programs functionality: Recive a frame with following format (Example): 0x7E 0x00 0x12 0x92 0x00 0x13 0xA2 0x00 0x40 0x71 0x03 0x75 0x79 0x86 0x01 0x01 0x00 0x00 0x01 0x00 0x2A 0x63 * The 1st byte (7E) is start-of-frame byte * The folloing 11 bytes (0x00 0x12 0x92 0x00 0x13 0xA2 0x00 0x40 0x71 0x03 0x75) are observed to be konstant in every message. * The last byte (0x63) is checksum * The two bytes (0x00 0x2A) before the checksum are importent and needed to be isolated. This to bytes hold the value of the temperatur When the value is isolated (Example: 0x00 0x2A) it needs to be converted to a temperatur value like this: From hex to decimal: 0x00 0x2A = 0x002A --> Decimal: 42 Temperature in celsius = 42*0732421875 ////////////////////////////// Programs GUI /////////////////////////////////// namespace ThermoCouple { public partial class ThermoCoupleViewer : Form { //Thermo Couple COMport Values string ThermoCOMportName; //Variables byte[] ByteBuffer = new byte[30]; AsynchIOThermo TempSensor; public ThermoCoupleViewer() { InitializeComponent(); string[] TermoPorts = SerialPort.GetPortNames(); TermoCoupleCOMComboBox.DataSource = TermoPorts; } //Buttons private void ExitButton_Click(object sender EventArgs e) {Close();} private void ConnectButton_Click(object sender EventArgs e) { ThermoCOMportName = TermoCoupleCOMComboBox.Text; TempSensor = new AsynchIOThermo(ThermoCOMportName 22); TempSensor.Run(); RefreshTime.Start(); DisconnectButton.Enabled = true; ConnectButton.Enabled = false; } private void DisconnectButton_Click(object sender EventArgs e) { TempSensor.Stop(); DisconnectButton.Enabled = false; ConnectButton.Enabled = true; } private void TermoCoupleRefreshCOMButton_Click(object sender EventArgs e) { string[] TermoPorts = SerialPort.GetPortNames(); TermoCoupleCOMComboBox.DataSource = TermoPorts; } private void RefreshTime_Tick(object sender EventArgs e) {TemperaturTextBox.Text = TempSensor.Temperatur;} } } //////////////////////////////////////// END //////////////////////////////////////////////

Karthik Agarwal · Answer

After seeing the code again i noticed that the initial port settings are wrong. What do you mean by giving the names directly like the way you gave in the code anyway try using these initial port settings. COMport.PortName = COM1; COMport.BaudRate = 4800; COMport.DataBits = 8; COMport.Parity = System.IO.Ports.Parity.None; COMport.StopBits = System.IO.Ports.StopBits.One; COMport.Handshake = Handshake.None; COMport.Encoding = Encoding.ASCII; COMport.ReadTimeout = -1; COMport.WriteTimeout = -1; COMport.ReceivedBytesThreshold = 1; COMport.ParityReplace = 0x3f; COMport.NewLine = 
; COMport.ReadBufferSize = 0x1000; COMport.WriteBufferSize = 0x800;

Karthik Agarwal · Answer

Then if u can explain me what your intention is exactly i can try creating a project and work on that which may require little more time. If you need more assistance do come up with the exact requirements what you are trying to do? Asynchronous reception alone doesn't say anything.

Haris · Answer

I trying to make an asynchronous reception. I am new to c# so maby i am doing it wrong.

Karthik Agarwal · Answer

i don't understand what you are trying to do with inputStream.BeginRead(buffer 0 buffer.Length myCallBack null);// 1st line You should have got the data already in output_buffer based on the following line this.COMport.Read(output_buffer 0 bytes_to_read); then what for you wrote the 1st line?

Haris · Answer

I have changed the OnCompletedRead() metod like this: //////////////////////////////////////////////////// CODE /////////////////////////////////////// byte[] output_buffer = new byte[100] public void OnCompletedRead(IAsyncResult asyncResult) { //int bytesRead = inputStream.EndRead(asyncResult); int bytes_to_read = this.COMport.BytesToRead; //if (bytesRead > 0) if (bytes_to_read > 0 ) { this.COMport.Read(output_buffer 0 bytes_to_read); Temperatur = ConvertToHex(Encoding.ASCII.GetString(output_buffer 0 bytes_to_read)); //Temperatur = ConvertToHex(Encoding.ASCII.GetString(buffer 0 bytesRead)); inputStream.BeginRead(buffer 0 buffer.Length myCallBack null); } } ////////////////////////////////////// END OF CODE ////////////////////////////////////////////// Still no full frame and my COMport read buffer gets full. :(