True.

I didn't consider that situation.  I use this for my own debugging/one-off
projects and have never actually passed anything to it other than a 0 or a 1 :)

Good suggestion.

Eric

On Mon, 16 Feb 2004 18:16:05 -0300
Lucas Hartmann <lhartmann@DETEC.UNIJUI.TCHE.BR> wrote:

> Eric,
>
> I've noticed that you initialized fd=0. Note that the swich statement has no
> default: clause, so calling the function with an out-of-range number (eg 5),
> will skip the open(...)'s and fd will keep as 0. When fd is checked for
> error it's compared -1 so it will return success in a wrong situation, just
> after calling the control functions on fd=0.
>
> Isn't a good idea to initialize fd=-1?
>
> Lucas Hartmann
>
> -------Mensagem original-------
>
> De: pic microcontroller discussion list
> Data: 02/16/04 17:45:04
> Para: PICLIST@MITVMA.MIT.EDU
> Assunto: Re: [EE]: Serial Port and Linux
>
> Are you opening the serial port with all the right options?  I've never had
> that
> happen, but it sounds like some sort of echo.  Do you know that the device
> you
> are reading from is not actually sending the newlines?
>
> Here is my serial port initialization function.  You'll need to set the
> options
> to what you need, but...  Maybe you will find something missing in your code
>
> I've used this exact code in several projects over the last year.  Including
> one
> just a few weeks ago, so I know it works.
>
> Just pass this function the port number and it returns a file descriptor to
> the
> open port.
>
>
> int initialize_serial(int port_num)
> {
>         struct termios options;
>         int fd=0;
>
>         //open port
>         switch(port_num)
>         {
>                 case 0:
>                         fd=open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
>                         break;
>                 case 1:
>                         fd=open("/dev/ttyS1", O_RDWR | O_NOCTTY | O_NDELAY);
>                         break;
>                 case 2:
>                         fd=open("/dev/ttyS2", O_RDWR | O_NOCTTY | O_NDELAY);
>                         break;
>                 case 3:
>                         fd=open("/dev/ttyS3", O_RDWR | O_NOCTTY | O_NDELAY);
>                         break;
>         }
>
>         //make sure it opened okay
>         if(fd==-1)
>         {
>                 printf("Error opening serial port\r\n");
>         }
>
>         fcntl(fd, F_SETFL, 0);
>
>         //get the current port options
>         tcgetattr(fd, &options);
>
>         //set baud rate
>         cfsetispeed(&options, B38400);
>         cfsetospeed(&options, B38400);
>
>         //set up port for 8N1
>         options.c_cflag |= (CLOCAL | CREAD);
>         options.c_cflag &= ~PARENB;
>         options.c_cflag &= ~CSTOPB;
>         options.c_cflag &= ~CSIZE;
>         options.c_cflag |= CS8;
>
>         //options.c_lflag |= (ICANON);
>         options.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL | ISIG);
>
>         options.c_cc[VTIME]=0;
>         options.c_cc[VMIN]=6;
>
>         //apply new settings
>         tcsetattr(fd, TCSANOW, &options);
>
>         return fd;
> }
>
>
>
> Good luck,
> Eric
>
>
>
> On Mon, 16 Feb 2004 15:12:28 -0500
> Herbert Graf <mailinglist2@FARCITE.NET> wrote:
>
> > Hello all,
> >
> > I'm trying to write a small program that sends a few things over a serial
> > port and then reads a few things back. I've having trouble getting it to
> > work.
> >
> > I'm using open, write and read to do my things, accessing the device
> through
> > the /dev/ttyS1 interface. Things work fine for a while and then seem to go
> > crazy. For example, I can send a few things down the line, but then when I
> > do a single byte read from the port I continuously get the newline
> > character.
> >
> > Anybody have some simple gcc compatible c code of accessing the serial
> port
> > in Linux? I'm using Redhat 9.0 and gcc. Thanks, TTYL
> >
> > ----------------------------------
> > Herbert's PIC Stuff:
> > http://repatch.dyndns.org:8383/pic_stuff/
> >
> > --
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