Subj : RS232 Serial Communication problem (Text capturing form telephone system)
To   : borland.public.cpp.borlandcpp
From : "JH Conradie" <npkmrb@intekom.co.za>
Date : Wed Jul 09 2003 01:38 pm

To anyone who can help!!!!

I purchased my Turbo C++ compiler back in 1992/93 and at that time
registered it at Softsource, PO Box 783244, Sandton, 2146, South Africa.

My Serial No on Disk 1 is "EA 143 A1006 5698"

I am currently trying to write a program in C, but as I have very little
experience with serial communications, I'm stuck right at the beginning.
I've consulted a couple of books and did a few searches on the internet, but
nothing seems to work, and I know the answer is very simple but I'm just
overlooking something.

Background information:

I am using Turbo C++ Ver3.0 for Dos.

My program should do the following simple task:

We have a Jupiter PBX telephone system, connected to the serial port of a
Epson LX300 printer.  The printer receives all the outgoing call
information. (Plain text only).  The serial port is configured as follows:

                        1200bps, 7 data bits, even parity, 1 stop bit

What I need to do is to capture the text intended for the printer and save
it to a file and then process the information.

I don't have a problem with the processing of the information in the text
file, but I don't get the capturing procedure to work.

There are only three wires connected to the printer's serial port:  (25 Pin
connector)
        Pin 3 - RX Data,
        Pin 4 - Request to send (Always positive according to the printer's
manual)
        Pin 7 - Signal Ground (Return path for data control characters
according to the printer's manual)

If I run the program listed below, the status of the port shows that no data
is received:
            Port status: 24624 - 0110 0000 0000 0000

After the first read of the port the status of the port changes to 12803 or
sometimes to 657.
            Port status: 12803 - 0011 0010 0000 0011 (Overrun error)
            Port status:      657 - 0000 0010 1001 0001  (Overrun error)

In both cases an overrun error is reported.  My conclusion is that I have to
control the RTS-line (Pin 4 on the connector) or I have to pulse Pin7 -
Signal Ground and I don't know how to manipulate the voltage level on a pin
of a port.

I've tried HyperTerminal in Windows 95. But HyperTerminal tries to
initialize the modem in the PBX system and no text is received - I've tried
all the available terminal types.

Then I downloaded a trial version of Telix from the internet and that works
perfectly in its Terminal mode when it is configured for 1200baud, even
parity, 7 data bits, 1 stop bit and the terminal type is ANSI-BBS. All flow
control options were disabled (Xon/Xoff, CTS/RTS, DSR/DTR). At least this
confirms that my cable is wired correctly.

I would appreciate it if anyone can help me with solving this problem!

Thank you
Johan

I copied moest of this program form Turbo C's help system.  It works fine
when 2 PC's are connected with a RS232 null modem cable.
#include <bios.h>#include <conio.h>
#include <stdio.h>#define COM_CHR7 0x02 /* 7 data bits */
#define COM_CHR8 0x03 /* 8 data bits */
#define COM_CHR8 0x03 /* 8 data bits */
#define COM_STOP1 0x00 /* 1 stop bit */
#define COM_STOP2 0x04 /* 2 stop bits */
#define COM_NOPARITY 0x00 /* No parity */
#define COM_ODDPARITY 0x08 /* Odd parity */
#define COM_EVENPARITY 0x18 /* Even parity */
#define COM_110 0x00 /* 110 baud */
#define COM_150 0x20 /* 150 baud */
#define COM_300 0x40 /* 300 baud */
#define COM_600 0x60 /* 600 baud */
#define COM_1200 0x80 /* 1200 baud */
#define COM_2400 0xA0 /* 2400 baud */
#define COM_4800 0xC0 /* 4800 baud */
#define COM_9600 0xE0 /* 9600 baud */
#define COM1 0
#define DATA_READY 0x100 /*1 0000 0000*/
#define TRUE 1
#define FALSE 0
#define SETTINGS ( COM_1200 | COM_EVENPARITY | COM_CHR7 | COM_STOP1)

int main(void)
{
   int in, out, status, DONE = FALSE;
   char ch;
   FILE *stream;
   bioscom(0, SETTINGS, COM1); /*Initialise COM1 for 1200,7bits,even,1
stop*/
   clrscr();
   cprintf("... BIOSCOM [ESC] to exit ...\r\n");
   while (!DONE)
  {
    status = bioscom(3, 0, COM1); /*Returns status of com1 port*/
    if (status & DATA_READY)
    {
       if ((out = bioscom(2, 0, COM1) & 0x7F) != 0) /*mask the 7 data bits*/
          putch(out); /*output to VDU*/
       if (out == 13)
         cprintf("\r\n");
    /* open a file for append */
    stream = fopen("TEL_LOG.TXT", "a+");
    fputc(out,stream); /*Write received data to file*/
    fclose(stream);
  }

if (kbhit())
{
  if ((in = getch()) == '\x1B') /*if ESc is hit*/
    DONE = TRUE;
  /*bioscom(1, in, COM1); send value of "in" to Com1*/
  bioscom(1,in, COM1);
}
}
return 0;
}


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