Re: Help serial port communication

[Carey Evans <c.evans@clear.net.nz>]

"Jens B. Jorgensen" <jjorgens@bdsinc.com> writes:

> Here's some code you can build on:
> 
>         struct termios  ti;
>         int             modem;
> 
>         modem = open("/dev/ttyS1", O_RDWR, 0);

I think it's generally necessary to do  O_RDWR|O_NONBLOCK  to open a
disconnected serial port, then set CLOCAL with termios, and finally
turn off O_NONBLOCK with fcntl.  Of course, for just setting the speed
it should be enough to change the open().

>         ioctl(modem, TCGETS, &ti); /* fill the termios struct with the current settings */
>         cfsetispeed(&ti, B9600); /* set input speed to 9600, could be B300 - B230400 */
>         cfsetospeed(&ti, B9600); /* set output speed */
>         ioctl(modem, TCSETS, &ti);
>         close(modem);

I prefer to use tcgetattr and tcsetattr than ioctl, although the end
result is exactly the same.

> You can check out the termios man page for more details.

Although it describes *how* to do it, it's a bit short on what and
why.  You could try looking at the source for things like minicom, dip
and pppd.

-- 
	 Carey Evans  http://home.clear.net.nz/pages/c.evans/

	  GNU GPL: "The Source will be with you... always."


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