Communications with device using STX/ETX/LRC

Hey guys!!
I am trying to communicate with an Ingenico iSC350 and I need some help with the following string.

STX control character
1 byte
Message Identifier
3 bytes
Message data, consisting of multiple fields
n bytes (0 to 241)
ETX control character
1 byte
LRC check character
1 byte

How do I go about this?


Who is Participating?
Minh Võ CôngConnect With a Mentor Commented:
Do you want parser message?
a line format like: STX(1)MsgID(3)MsgData(0-241)EXT(1)LRC(1)
in C# string is unicode
string strMsg = <STX>midmessagedata<EXT><LRC>;
char STX = (char)0x02;
char ETX = (char)0x03;
strmsgid = strMsg.Substring(1,3); //now strmsgid = "mid"
//convert to byte array
byte [] id = Encoding.ASCII.GetBytes(strmsgid);
int i = strMsg.IndexOf(ETX);
strmsgdata = strMsg.Substring(4,i-4);// strmsgdata  = "messagedata"
charLRC = strMsg[strMsg.Leng-1];
JDL129Author Commented:
minhvc!!!!!!!!!!!!!  I am glad to hear from you.  You get the points but I need some clarification.

What you have sent is exactly what I need.  I have some data to send and I would appreciate it if you can put it in the format above.

My open message is 01.00000000
My close message is 00.0000

 STX an ASCII control Character, Type is Constant, and length is 1
Message Identifier is ASCII "01." for open message
Application ID is Decimal 0000
Parameter ID is Decimal 0000
ETX is an ASCII control Character Type is Constant, length is 1
LRC check character is Binary, length is 1

When it is sent it looks like 01.00000000

When I run int i = strMsg.IndexOf(ETX);  i is -1.
I don't think I have items in the proper order.

Again I appreciate the post!!!!

JDL129Author Commented:
Thanks a bunch!!!!!!!!!!!!!111
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Minh Võ CôngCommented:
How your PC connect to Ingenico iSC350? Com (serial port) or IP (Socket, NET)? Can you post the code you have send/receive data? Do you receive a byte [] or string data?
JDL129Author Commented:
Thanks for the post!!!!!!!!!

It connects by usb: RemoteHost is and RemotePort is 5446 and it has a Telnet button beside the Host and Port fields.

When I parse the received data it appears to be the same format as you have suggested we send.

This is the code we're trying to use:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

using System.Net.Sockets;
using System.IO;
using System.Threading;
using System.Net;

namespace iSC350
    public partial class Form1 : Form
        public Form1()
        TcpListener listener = null;
        private void btnSend_Click(object sender, EventArgs e)
             string strMsg = "<STX>"+txtMessage.Text+"<FS>"+txtBoxId.Text+"<FS>7699<ETX><LRC>";
            TcpClient tcpClient = new TcpClient();
            tcpClient.Connect("", 5446);
            NetworkStream Streamtest = tcpClient.GetStream();

            Byte[] outbytes = System.Text.Encoding.Default.GetBytes(strMsg.ToCharArray());
            Streamtest.Write(outbytes, 0, outbytes.Length);//Sned data to ISC350 port


      private void AcceptWorkThread()
            while (true)
                Socket socket = listener.AcceptSocket();
                byte[] buffer = new byte[1024];
                int receiveCount = socket.Receive(buffer);
                if (receiveCount > 0)
                    string recString = Encoding.UTF8.GetString(buffer, 0, receiveCount);  
                   MessageBox.Show(recString,"ISC350 Port get data.");


      private void Form1_Load(object sender, EventArgs e)
          listener = new TcpListener(new IPEndPoint(IPAddress.Parse(""), 5446));
          listener.Start();//Listen ISC350 port if get data
          Thread acceptThread = new Thread(new ThreadStart(AcceptWorkThread));

Thanks again for the help!!!

Minh Võ CôngCommented:
How recString you received from device?
JDL129Author Commented:

We haven't got to there yet.  Any ideas?

Thanks again,

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