I have a MEI Cashflow E7900 and an MDB adapter for connecting a device to a serial port. The store that sold me the adapter also provided a test application written in Delphi compiled with Borland Delphi v6.0. It works fine, but for some reason my code doesn’t.
When you use MDB, you need to send a POLL command every 200 ms. If everything is in order, the coin changer sends ACK . When I submit it using a Delphi application, the session looks like this:
=> 0x0B * 0x0B (A star symbol means that parity is set to Mark. By default, parity is a space)
<= 0x00
So that's all right, that’s what I expect. When I send POLL using a C # application, it looks like this:
=> 0x0B * 0x0B
<= 0x3F 0x00
Sometimes a coin changer sends me 0x3F 0x11 after POLL , which makes no sense, there is no valid answer like this. When I get such a response, I launch the Delphi application and get a valid ACK response. I used the sniffer COM port to make sure that there is no difference in the data sent, including the port configuration, and I continue to receive different responses.
Here is the source code of the test application (Delphi):
<...> //The component used it called BComPort form1.BComPort1.BaudRate:=br9600; form1.BComPort1.Parity:=paSpace; form1.BComPort1.Port:="%port name goes here%"; form1.BComPort1.Open; <...> 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; <...> 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);
A complete list of codes is available here , but the code given here should be sufficient.
My code (C #):
private const byte P_ADDRESS = 0x8; static void Main(string[] args) { <...> 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; <...> } 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 > 0) port.Write(data, 0, data.Length); port.Write(new byte[] { crc }, 0, 1); }
Polling a command with a Delphi application:
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 ; .
Poll team with my application:
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 ; .
The resulting data seems almost the same, with the exception of 0x3F at the beginning. But the behavior of the device is also different, it seems that it is not connected to the PC, it says “Disabled by machine” when I use the C # application and “Status OK” when I use the Delphi application. Could this be due to the .NET Framework? Any library names for interacting with COM ports are described.
I have an idea why I get different answers. Maybe I hope someone here helps me. Thanks in advance. Also thanks for reading this huge question.