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-----Original Message-----
From: Gabriel Paubert [mailto:paubert@iram.es]
Sent: Friday, January 27, 2006 9:04 PM
To: Robbie
Cc: debian-embedded@lists.debian.org
Subject: Re: termios ifnterface, raw?
On Fri, Jan 27, 2006 at 02:44:34PM -0500, Robbie wrote:
>
> Hi,
> I'm using the program below to grab data from the serial port. The data is
in a predefined language and does not follow the typical character set, but
sending commands.
>
> The hex values I've received is in no way close to that being send and
I've tried just about every configuration I can think of. The raw data 0x02
for instance signifies the start of a message and that's no where to be
found. I'm using a non return to zero format: 1 start bit, 8 data bits, no
parity, and one stop.
> Can any one offer any insight into this? What am I missing?
> Thanks a lot.
>
> listing:
> main()
> {
> struct termios oldtio,newtio;
> struct sigaction saio; /* definition of signal action */
> int inx = 0;
> /* open the device to be non-blocking (read will return
immediatly) */
> fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NONBLOCK);
> if (fd <0) {perror("/dev/ttyS0"); exit(-1); }
>
> /* install the signal handler before making the device
asynchronous */
> saio.sa_handler = signal_handler_IO;
> // saio.sa_mask = 0;
> saio.sa_flags = 0;
> saio.sa_restorer = NULL;
> sigaction(SIGIO,&saio,NULL);
>
> /* allow the process to receive SIGIO */
> fcntl(fd, F_SETOWN, getpid());
> /* Make the file descriptor asynchronous */
> fcntl(fd, F_SETFL, FASYNC);
>
> tcgetattr(fd,&oldtio);
> newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
> newtio.c_iflag = IGNPAR | ICRNL;
> newtio.c_oflag = 0;
> newtio.c_lflag = ICANON;
> newtio.c_cc[VMIN]=0;
> newtio.c_cc[VTIME]=0;
> tcflush(fd, TCIFLUSH);
> tcsetattr(fd,TCSANOW,&newtio);
You have junk in almost all control character locations of newtio, possibly
not even reproducible from run to run since it is allocated on the stack.
You could for example copy oldtio to newtio to start from an existing and
hopefully working (even if it's not what you want) state.
Besides that setting ICANON and cc[VMIN] or cc[VTIME] is inconsistent since
man termios claims:
These symbolic subscript values are all different, except that VTIME, VMIN
may have the same value as VEOL, VEOF, respectively.
(In non-canonical mode the special character meaning is replaced by the
timeout meaning.
...)
As already mentioned, cfmakeraw may help you. I don't know what you mean by
BAUDRATE, since I've not found this constant on my system.
Regards,
Gabriel
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