tcsetattr() in termios not working correctly

[ev8r]

basically, here is what im using to initialize a serial port to 9600 baud, and 8 N 1.

int fd;
struct termios options;
fd=open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
if (fd==-1)
return (-1);
fcntl(fd, F_SETFL, 0);
tcgetattr(fd,&options);
options.c_ispeed=9600;
options.c_ospeed=9600;
printf("speed = %i bps \n",(int)options.c_ispeed);
options.c_cflag |= (CLOCAL | CREAD);
options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
options.c_cflag &= ~CSTOPB;
options.c_cflag |= CS8;
options.c_cc[VMIN] = 0;
options.c_cc[VTIME] =10;
tcsetattr(fd,TCSANOW,&options);

while this program runs i do a stty -F /dev/ttyS0 and here is what i get:

speed 0 baud; line = 0;
min = 0; time = 10;
ignbrk -brkint -icrnl -imaxbel
-opost -onlcr
-isig -icanon -iexten -echo -echoe -echok -echoctl -echoke

(and of course no data flow on the port)

notice the 'speed 0 baud', i know this serial port functions correctly as i've used minicom on it many times, perhaps someone can shed some light on this little dilemma for me.

thnxs

[tecknophreak]

You might not use these same flags, but here's how to setup serial termios from serial programming how-to

        termios oldtio, newtio;
        tcgetattr(sfd, &oldtio);
	bzero(&newtio, sizeof(newtio));

	newtio.c_cflag = B9600 | CS8 | CLOCAL | CREAD;
CREAD;
	newtio.c_iflag = IGNPAR | ICRNL;
	newtio.c_oflag = 0;
	newtio.c_lflag = 0;//ICANON; //0;

        newtio.c_cc[VINTR]    = 0;     /* Ctrl-c */
        newtio.c_cc[VQUIT]    = 0;     /* Ctrl-\ */
        newtio.c_cc[VERASE]   = 0;     /* del */
        newtio.c_cc[VKILL]    = 0;     /* @ */
        newtio.c_cc[VEOF]     = 4;     /* Ctrl-d */
        newtio.c_cc[VTIME]    = 0;     /* inter-character timer unused */
        newtio.c_cc[VMIN]     = 1;     /* blocking read until 1 character arrives */
        newtio.c_cc[VSWTC]    = 0;     /* '\0' */
        newtio.c_cc[VSTART]   = 0;     /* Ctrl-q */
        newtio.c_cc[VSTOP]    = 0;     /* Ctrl-s */
        newtio.c_cc[VSUSP]    = 0;     /* Ctrl-z */
        newtio.c_cc[VEOL]     = 0;     /* '\0' */
        newtio.c_cc[VREPRINT] = 0;     /* Ctrl-r */
        newtio.c_cc[VDISCARD] = 0;     /* Ctrl-u */
        newtio.c_cc[VWERASE]  = 0;     /* Ctrl-w */
        newtio.c_cc[VLNEXT]   = 0;     /* Ctrl-v */
        newtio.c_cc[VEOL2]    = 0;     /* '\0' */

	tcflush(sfd, TCIFLUSH);
	tcsetattr(sfd, TCSANOW, &newtio);

[tecknophreak]

Originally posted by ev8r

options.c_cflag |= (CLOCAL | CREAD);
options.c_cflag &= ~CSTOPB;

thnxs

add B9600 to c_cflag, should fix it.

[ev8r]

works great!!!!

THANKS !!!!!!!!!!!!

[victoryman]

You might not use these same flags, but here's how to setup serial termios from serial programming how-to

        termios oldtio, newtio;
        tcgetattr(sfd, &oldtio);
	bzero(&newtio, sizeof(newtio));

	newtio.c_cflag = B9600 | CS8 | CLOCAL | CREAD;
CREAD;
	newtio.c_iflag = IGNPAR | ICRNL;
	newtio.c_oflag = 0;
	newtio.c_lflag = 0;//ICANON; //0;

        newtio.c_cc[VINTR]    = 0;     /* Ctrl-c */
        newtio.c_cc[VQUIT]    = 0;     /* Ctrl-\ */
        newtio.c_cc[VERASE]   = 0;     /* del */
        newtio.c_cc[VKILL]    = 0;     /* @ */
        newtio.c_cc[VEOF]     = 4;     /* Ctrl-d */
        newtio.c_cc[VTIME]    = 0;     /* inter-character timer unused */
        newtio.c_cc[VMIN]     = 1;     /* blocking read until 1 character arrives */
        newtio.c_cc[VSWTC]    = 0;     /* '\0' */
        newtio.c_cc[VSTART]   = 0;     /* Ctrl-q */
        newtio.c_cc[VSTOP]    = 0;     /* Ctrl-s */
        newtio.c_cc[VSUSP]    = 0;     /* Ctrl-z */
        newtio.c_cc[VEOL]     = 0;     /* '\0' */
        newtio.c_cc[VREPRINT] = 0;     /* Ctrl-r */
        newtio.c_cc[VDISCARD] = 0;     /* Ctrl-u */
        newtio.c_cc[VWERASE]  = 0;     /* Ctrl-w */
        newtio.c_cc[VLNEXT]   = 0;     /* Ctrl-v */
        newtio.c_cc[VEOL2]    = 0;     /* '\0' */

	tcflush(sfd, TCIFLUSH);
	tcsetattr(sfd, TCSANOW, &newtio);

Yes... you are right... even 20 years later, adding the baud rate to the c_cflag works for me:

options.c_cflag = B921600 | CS8 | CLOCAL | CREAD; // 8N1 mode