From owner-freebsd-hackers  Thu Jun 28 17:30:46 2001
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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
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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