root@MCIRPS2.MED.NYU.EDU (05/03/90)
I am trying to set the ioctl call so that a raw read from a
serial port will time out after a few seconds. No matter what I
set the TIME value for in the control structure, the machine
still hangs waiting for characters. What am I doing wrong, if anything.
Code follows:
---
new_settings.c_iflag = IGNBRK | IGNPAR;
new_settings.c_oflag = NULL;
new_settings.c_cflag = B9600 | CS8 | CREAD | CLOCAL;
new_settings.c_lflag = ICANON;
new_settings.c_line = NULL;
new_settings.c_cc[0] = NULL;
new_settings.c_cc[1] = NULL;
new_settings.c_cc[2] = NULL;
new_settings.c_cc[3] = NULL;
new_settings.c_cc[4] = NULL;
new_settings.c_cc[5] = TIMEOUT;
ioctl(fd, TCSETA, &new_settings);
-----
A read that has timed out should return with a value of 0. Right ?
dan.
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+-----------------------------------------------------------------------------+moss@BRL.MIL ("Gary S. Moss", VLD/VMB) (05/03/90)
< I am trying to set the ioctl call so that a raw read from a < serial port will time out after a few seconds. No matter what I < set the TIME value for in the control structure, the machine < still hangs waiting for characters. What am I doing wrong, if anything. < new_settings.c_iflag = IGNBRK | IGNPAR; < new_settings.c_oflag = NULL; < new_settings.c_cflag = B9600 | CS8 | CREAD | CLOCAL; < new_settings.c_lflag = ICANON; < new_settings.c_line = NULL; < new_settings.c_cc[0] = NULL; < new_settings.c_cc[1] = NULL; < new_settings.c_cc[2] = NULL; < new_settings.c_cc[3] = NULL; < new_settings.c_cc[4] = NULL; < new_settings.c_cc[5] = TIMEOUT; For one thing, if you set ICANON, you will not get RAW input; do the following instead. Also, if you want to get 1 character at a time without blocking, set the VMIN (element 4) of c_cc to 1, and set TIMEOUT to 0. new_settings.c_lflag &= ~ICANON; /* Canonical input OFF. */ new_settings.c_cc[VMIN] = 1; new_settings.c_cc[VTIME] = 0; Other indices for c_cc should be written using their mnemonics as defined in /usr/include/sys/termio.h for portability if nothing else. CAVIAT: the VMIN/VTIME mechanism is intended for reading DMA bursts, and does not really work for general timeouts. What you probably need to use poll(2) or select(2) rather than ioctl(2) (if I understand your question).
root@sgzh.uucp (Bruno Pape) (05/04/90)
In article <9005030929.aa08086@VMB.BRL.MIL> moss@BRL.MIL ("Gary S. Moss", VLD/VMB) writes: >< I am trying to set the ioctl call so that a raw read from a >< serial port will time out after a few seconds. No matter what I >< set the TIME value for in the control structure, the machine >< still hangs waiting for characters. What am I doing wrong, if anything. >< >< new_settings.c_iflag = IGNBRK | IGNPAR; >< new_settings.c_oflag = NULL; >< new_settings.c_cflag = B9600 | CS8 | CREAD | CLOCAL; >< new_settings.c_lflag = ICANON; >< new_settings.c_line = NULL; >< new_settings.c_cc[0] = NULL; >< new_settings.c_cc[1] = NULL; >< new_settings.c_cc[2] = NULL; >< new_settings.c_cc[3] = NULL; >< new_settings.c_cc[4] = NULL; >< new_settings.c_cc[5] = TIMEOUT; > > >For one thing, if you set ICANON, you will not get RAW input; do the >following instead. Also, if you want to get 1 character at a time >without blocking, set the VMIN (element 4) of c_cc to 1, and set >TIMEOUT to 0. > >new_settings.c_lflag &= ~ICANON; /* Canonical input OFF. */ >new_settings.c_cc[VMIN] = 1; >new_settings.c_cc[VTIME] = 0; > >Other indices for c_cc should be written using their mnemonics as defined >in /usr/include/sys/termio.h for portability if nothing else. > >CAVIAT: the VMIN/VTIME mechanism is intended for reading DMA bursts, and >does not really work for general timeouts. What you probably need to >use poll(2) or select(2) rather than ioctl(2) (if I understand your >question). While the above is along the right path it too will hang forever waiting for one character. If he wants it to time out at some point I believe the following would work better. Replace delay with the number of seconds you want it to wait before timing out. tty.c_iflag = 0; tty.c_oflag = 0; tty.c_cflag = B9600 | CS8 | CREAD; tty.c_lflag = 0; tty.c_cc[VTIME] = delay; tty.c_cc[VMIN] = 0; if ( ioctl( descriptor, TCSETA, &tty ) < 0 ) perror("ioctl"); Bruno With 999999 possiblities between "cooked" and "raw" you know you're not going to have any fun. Boo hoo.
vjs@rhyolite.wpd.sgi.com (Vernon Schryver) (05/06/90)
The VTIME parameter is in units of tenths of seconds, not seconds. The FIONBIO ioctl works on IRIX TTY's, to give "non-block" I/O. Using select(2) is almost certainly the best solution. Vernon Schryver vjs@sgi.com
root@sgzh.uucp (Bruno Pape) (05/08/90)
In article <59374@sgi.sgi.com> vjs@sgi.com (Vernon Schryver) writes: > >The VTIME parameter is in units of tenths of seconds, not seconds. > >The FIONBIO ioctl works on IRIX TTY's, to give "non-block" I/O. > >Using select(2) is almost certainly the best solution. > Opps, tenths of a seconds it is. Non-blocking I/O and non-blocking with a delay are slightly different. Select seems like overkill for simple tty I/O. Why is it almost certainly the best solution? To all non-blocking tty I/O problems? Just wondering, Bruno