Mail Archives: cygwin/1999/08/24/01:39:30
Why not combine the two?
Use open() to startup, and set the control, then fdopen()
once the configuration is established and you are happy to
just read and write?
Just a thought :)
--Geoff
Kim Poulsen wrote:
>
> Chris,
>
> The problem with fopen() is that it returns a FILE* where open() return
> an int. fopen() is way to advanced for use with serial port I/O as
> the concept of a FILE is meaningless on a serial channel i.e. there is
> no name or path etc. associated with a raw serial stream. In
> addition read() and write() uses an int file descriptor and not a FILE*.
> The open(), read(), and write() functions are the most low level
> I/O handling ANSI C can handle. The f*() functions are all built on
> these functions. If I use fopen() I have no way of controlling the
> channel characteristics such as baud rate, bits, parity etc. This
> I can do with the int returned from the open() function.
> If however you should have some running code (the code below _will_
> run) using fopen() I'd sure like to see it for the educational value.
>
> Thanks for your response.
> /Kim
>
> PS: Why are you posting everything twice ?
>
> Chris Faylor wrote:
> >
> > On Mon, Aug 23, 1999 at 11:49:37AM +0200, Kim Poulsen wrote:
> > >Corinna Vinschen wrote:
> > >> Kim Poulsen wrote:
> > >> > I've got the following problem:
> > >> > I need to access the serial ports of my PC through an ANSI C program.
> > >> > How do I do that ? I have already tried using fopen("/dev/com2", "r")
> > >> > and fopen("com2", "r") but these only causes a core dump.
> > >> > [...]
> > >> AFAIK this is a known problem in b20.1. Try to use a newer snapshot.
> > >
> > >I have the problem solved. A a contribution to the mailing list I
> > >submit the solution to the problem below.
> >
> > I'm not sure how this solves your problem. You aren't using fopen. That
> > appears to be it.
> >
> > As is so often the case, with these kinds of problems, simply running the
> > program using gdb would have probably provided worlds of information for
> > debugging the problem.
> >
> > If the code sample below is getting you running, then fine. It is not
> > a generic solution for people who want to use stdio for serial I/O,
> > however. AFAIK, that does work.
> >
> > -chris
> >
> > >#include <fcntl.h>
> > >#include <termios.h>
> > >#include <stdio.h>
> > >#include <unistd.h>
> > >
> > >#define BAUDRATE B9600
> > >#define MODEMDEVICE "com2"
> > >
> > >main()
> > >{
> > > int fd,c, n;
> > > char str[2];
> > > struct termios options;
> > >
> > > fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY );
> > > if (fd <0) {perror(MODEMDEVICE); exit(-1); }
> > >
> > > options.c_cflag = BAUDRATE;
> > > options.c_cflag &= ~CSIZE; /* Mask the character size bits */
> > > options.c_cflag |= CS8; /* Select 8 data bits */
> > >
> > > /* Write something */
> > > n = write(fd, "UART is functional\n\r", 19);
> > > if (n < 0)
> > > puts("write() of 19 bytes failed!");
> > >
> > > /* Make read() return immediately */
> > > fcntl(fd, F_SETFL, FNDELAY);
> > >
> > > /* Read something until 'Q' recieved */
> > > while(str[0] != 'Q') {
> > > if(read(fd, str, 1) != -1) {
> > > printf("%s\n", str);
> > > }
> > > }
> > >}
> >
> > --
> > Want to unsubscribe from this list?
> > Send a message to cygwin-unsubscribe AT sourceware DOT cygnus DOT com
>
> --
> Kim Poulsen, B.Sc.E.E, System Developer HW
> Ericsson Telebit A/S Tel: + 45 86 28 81 76
> Fabriksvej 11 Fax: + 45 86 28 81 86
> DK-8260 Viby J E-mail: info AT tbit DOT dk
> Denmark URL: http://www.tbit.dk/
>
> --
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