Date: Thu, 28 Jun 2001 20:30:38 -0400 (EDT) From: Jason Borkowsky <jcborkow@tcpns.com> To: freebsd-hackers@freebsd.org Subject: Re: Serial port control Message-ID: <Pine.BSF.4.21.0106282024030.23341-100000@bemused.tcpns.com> In-Reply-To: <20010628160723.C21188@peitho.fxp.org>
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> > I am looking to find a simple way to control a serial port through BSD
> > (such as raising and lowering DTR for a specified duration). I thought I
> > had it using ioctl() and wrote a simple program to test it, but it seems I
> > don't have a full understanding of ioctl(). Does anyone know of any
> > pre-written utilities I can use? Or where to get some really detailed
> > information about ioctl()? Thanks!
After several responses, I thought I had it. From a software point of
view, my program, included below, works fine. But from a hardware point of
view, the signals I am trying to lower, RTS and DTR, are staying
high. Can anyone try to compile the below program and do a serial port
test with an RS-232 tester and see if anyone actually sees RTS and DTR
going low? Sorry for bothering everyone with this again, but this is
driving me nuts and I can't figure out the problem now. Thanks!
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
main () {
int fd; /* File descriptor for serial port */
int status; /* Serial port status bitmask */
int error = 0;
fd = open("/dev/cuaa0", O_RDWR | O_NOCTTY | O_NDELAY);
if (fd == -1)
perror("open_port: Unable to open /dev/ttyf1 - ");
else
error = fcntl(fd, F_SETFL, 0);
if (error == -1)
perror("fcntl error - ");
/* Get serial line status bitmask */
error = 0;
error = ioctl(fd,TIOCMGET,&status);
if (error == -1)
perror("ioctl1 GET error - ");
/* Signal Values
*
* 1 - DSR (Data Set Ready)
* 2 - DTR (Data Terminal Ready)
* 4 - RTS (Request to Send)
* 8 - ST (Secondary Transmit)
* 16 - SR (Secondary Receive)
* 32 - CTS (Clear to Send)
* 64 - DCD (Data Carrier Detect)
* 128 - RNG (Ring)
* 256 - DSR (Data Set Ready)
*/
printf ("Current Serial Settings:");
if (status >= TIOCM_DSR) {
status -= TIOCM_DSR;
printf (" DSR ");
}
if (status >= TIOCM_RNG) {
status -= TIOCM_RNG;
printf (" Ring ");
}
if (status >= TIOCM_CD) {
status -= TIOCM_CD;
printf (" DCD ");
}
if (status >= TIOCM_CTS) {
status -= TIOCM_CTS;
printf (" CTS ");
}
if (status >= TIOCM_SR) {
status -= TIOCM_SR;
printf (" SR ");
}
if (status >= TIOCM_ST) {
status -= TIOCM_ST;
printf (" ST ");
}
if (status >= TIOCM_RTS) {
status -= TIOCM_RTS;
printf (" RTS ");
}
if (status >= TIOCM_DTR) {
status -= TIOCM_DTR;
printf (" DTR ");
}
if (status >= TIOCM_LE) {
status -= TIOCM_LE;
printf (" DSR ");
}
printf("\n");
/* Lower DTR and RTS */
status = 1;
error = 0;
error = ioctl(fd,TIOCMSET,&status);
if (error == -1)
perror ("ioctl SET error - ");
/* Hold the signals low, as they seem to reset when releasing the
* file descriptor
*/
sleep(10);
error = 0;
error = ioctl(fd,TIOCMGET,&status);
if (error == -1)
perror ("ioctl GET error - ");
printf ("Current Serial Settings:");
if (status >= TIOCM_DSR) {
status -= TIOCM_DSR;
printf (" DSR ");
}
if (status >= TIOCM_RNG) {
status -= TIOCM_RNG;
printf (" Ring ");
}
if (status >= TIOCM_CD) {
status -= TIOCM_CD;
printf (" DCD ");
}
if (status >= TIOCM_CTS) {
status -= TIOCM_CTS;
printf (" CTS ");
}
if (status >= TIOCM_SR) {
status -= TIOCM_SR;
printf (" SR ");
}
if (status >= TIOCM_ST) {
status -= TIOCM_ST;
printf (" ST ");
}
if (status >= TIOCM_RTS) {
status -= TIOCM_RTS;
printf (" RTS ");
}
if (status >= TIOCM_DTR) {
status -= TIOCM_DTR;
printf (" DTR ");
}
if (status >= TIOCM_LE) {
status -= TIOCM_LE;
printf (" DSR ");
}
printf("\n");
close(fd);
}
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