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POInteracting with a coin changer using COM port
 

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  1. POInteracting with a coin changer using COM port
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    <p>I have a coin changer <code>MEI Cashflow E7900</code> and an MDB adapter to connect the device to a serial port. The shop which sold me the adapter also provided a test application, which is written in Delphi, compiled with Borland Delphi v6.0. It works perfectly, but my code for some reason does not.<br> When you use MDB you have to send <code>POLL</code> command every 200ms. If everything is OK, the Coin changer sends <code>ACK</code>. When I send it using Delphi application the session looks like this: </p> <blockquote> <p>=> 0x0B* 0x0B (The star character means parity set to Mark. By default parity is Space)<br> &lt;= 0x00</p> </blockquote> <p>So everything is OK, that is what I am expecting. When I send <code>POLL</code> with the C# application it is like:</p> <blockquote> <p>=> 0x0B* 0x0B<br> &lt;= 0x3F 0x00</p> </blockquote> <p>Sometimes the coin changer sends me <code>0x3F 0x11</code> after <code>POLL</code> which makes no sense, there is no any valid response like this. When I get such a response I run the Delphi application, and it gets a valid <code>ACK</code> response. I was using a COM port sniffer to make sure that there's no any difference in the data sent, including the port configuration itself and I keep getting different response.<br> Here goes the source code for the test application (Delphi):</p> <pre><code>&lt;...&gt; //The component used it called BComPort form1.BComPort1.BaudRate:=br9600; form1.BComPort1.Parity:=paSpace; form1.BComPort1.Port:="%port name goes here%"; form1.BComPort1.Open; &lt;...&gt; procedure SetModeBit(modebit:boolean); begin if modebit then begin form1.BComPort1.BeginUpdate; form1.BComPort1.Parity:=paMark; form1.BComPort1.EndUpdate; end else begin form1.BComPort1.BeginUpdate; form1.BComPort1.Parity:=paSpace; form1.BComPort1.EndUpdate; end; procedure TForm1.PollTimer(Sender: TObject); var s,buf,buf2:string; i,len:integer; x,adr,dat1,ack,chk:byte; crc:integer; &lt;...&gt; adr:=$08 or $0B; SetModeBit(true); form1.BComPort1.Write(adr,1); dat1:=0; crc:=adr + dat1; try s:=inttohex(crc,10); s:=s[length(s)-1]+s[length(s)]; chk:=strtoint('$'+s); except end; SetModeBit(false); form1.BComPort1.Write(chk,1); </code></pre> <p>Full code listing available <a href="https://dl.dropbox.com/u/19208429/Unit1.pas" rel="nofollow">here</a>, but the code provided here should be enough. </p> <p>My code (C#):</p> <pre><code> private const byte P_ADDRESS = 0x8; static void Main(string[] args) { &lt;...&gt; port = new SerialPort(ports[index]); port.BaudRate = 9600; port.StopBits = StopBits.One; port.DataBits = 8; port.DtrEnable = true; port.RtsEnable = true; port.Parity = Parity.Space; &lt;...&gt; } private static void onDataReceived(object sender, SerialDataReceivedEventArgs e) { byte[] dataReceived = new byte[port.BytesToRead]; SetModeBit(false); port.Read(dataReceived, 0, dataReceived.Length); Console.WriteLine("Data received:"); foreach (Byte b in dataReceived) { Console.Write(b.ToString("X") + " "); } Console.WriteLine(); } private static void SetModeBit(Boolean mode) { port.Parity = mode ? Parity.Mark : Parity.Space; } private static void SendData(Byte cmd, Byte[] data) { byte adr = (byte)(P_ADDRESS | cmd); byte crc = adr; foreach (var b in data) crc += b; SetModeBit(true); port.Write(new byte[] { adr }, 0, 1); SetModeBit(false); if (data.Length &gt; 0) port.Write(data, 0, data.Length); port.Write(new byte[] { crc }, 0, 1); } </code></pre> <hr> <p>Poll command with the Delphi application:</p> <pre><code>17.08.2012 18:05:18 COM8 Capture Started 17.08.2012 18:05:38 COM8 Opened By Process ID=2872 17.08.2012 18:05:38 Baud Rate =9600 17.08.2012 18:05:38 RTS Signal = True 17.08.2012 18:05:38 DTR Signal = True 17.08.2012 18:05:38 Line Control Change: SPACE-8-1 17.08.2012 18:05:38 Baud Rate =9600 17.08.2012 18:05:38 RTS Signal = True 17.08.2012 18:05:38 DTR Signal = True 17.08.2012 18:05:38 Line Control Change: MARK-8-1 17.08.2012 18:05:38 Write 1 Bytes: 0B ; . 17.08.2012 18:05:38 Baud Rate =9600 17.08.2012 18:05:38 RTS Signal = True 17.08.2012 18:05:38 DTR Signal = True 17.08.2012 18:05:38 Line Control Change: SPACE-8-1 17.08.2012 18:05:38 Write 1 Bytes: 0B ; . 17.08.2012 18:05:38 GetCommStatus Result:16 17.08.2012 18:05:38 Parity Error = True 17.08.2012 18:05:38 Baud Rate =9600 17.08.2012 18:05:38 RTS Signal = True 17.08.2012 18:05:38 DTR Signal = True 17.08.2012 18:05:38 Line Control Change: SPACE-8-1 17.08.2012 18:05:38 Read 1 Bytes: 00 ; . </code></pre> <p>Poll command with my application:</p> <pre><code>17.08.2012 18:12:08 COM8 Capture Started 17.08.2012 18:12:11 COM8 Opened By Process ID=3164 17.08.2012 18:12:11 Baud Rate =9600 17.08.2012 18:12:11 RTS Signal = True 17.08.2012 18:12:11 DTR Signal = False 17.08.2012 18:12:11 Line Control Change: SPACE-8-1 17.08.2012 18:12:11 Baud Rate =9600 17.08.2012 18:12:11 RTS Signal = True 17.08.2012 18:12:11 DTR Signal = True 17.08.2012 18:12:11 Line Control Change: SPACE-8-1 17.08.2012 18:12:11 DTR Signal = True 17.08.2012 18:12:11 Baud Rate =9600 17.08.2012 18:12:11 RTS Signal = True 17.08.2012 18:12:11 DTR Signal = True 17.08.2012 18:12:11 Line Control Change: MARK-8-1 17.08.2012 18:12:11 Write 1 Bytes: 0B ; . 17.08.2012 18:12:11 Baud Rate =9600 17.08.2012 18:12:11 RTS Signal = True 17.08.2012 18:12:11 DTR Signal = True 17.08.2012 18:12:11 Line Control Change: SPACE-8-1 17.08.2012 18:12:11 Write 1 Bytes: 0B ; . 17.08.2012 18:12:11 GetCommStatus Result:16 17.08.2012 18:12:11 Parity Error = True 17.08.2012 18:12:11 Read 1 Bytes: 3F ; ? 17.08.2012 18:12:11 Read 1 Bytes: 00 ; . </code></pre> <p>The data received seems to be almost the same, except <code>0x3F</code> in the beginning. But the device behaviour is different too, it does not seem to be connected to the PC, it says "Disabled by machine", when I use C# application, and "Status OK" when I use Delphi application. May this be happening because of the .NET Framework? Any names of libraries for COM port interaction are appretiated.</p> <p>I have idea, why I get different response. May be I hope someone here would help me. Thanks in advance. Also thanks for reading this huge question.</p>
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    1. COProvide an example of the data you recieve and what you actually expect. You should also clarify this statement "It works perfectly, but my code for some reason does not." because it seems your trying to indicate your sample application works but your code does not which of course makes no sense.
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    2. CODelphi version? I voted to close because nobody can guess why you don't understand this protocol or this device's behaviour.
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      1. USWarren P
    3. COWhy do you think so? I understand how everything works, I have no idea, why I get different response from the device, if I send same data to it, just using different programming languages.
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