Hi,
On Tue, Aug 31, 2010 at 06:37:54PM -0700, Shane W wrote:
> The other issue I see is that sizeof(buff) may or may not
> be the expected return.
>
> char buff[1024];
> sizeof(buff) = 1024
> char *buff;
> buff = malloc(1024);
> sizeof(buff) = 4 or 8 depending
another good point.
>
> So I would rework this entire function using poll with a
> timeout rather than read which could block indefinitely and
> a well defined io mechanism.
I don't think there is anything necessarily wrong with using blocking
io.
Trev
>
> Shane
> On Tue, Aug 31, 2010 at 04:31:05PM -0400, Trevor Saunders wrote:
> > Hi,
> >
> > > { /*Receive incoming serial data.*/
> > > STOP=FALSE;
> > > res = 0; /*eventually shows where buffer ends*/
> > > sleep(1);
> > > /*Force a wait to cause receive buffer to stabilize.*/
> > > while (STOP==FALSE) { /* loop for input */
> > >
> > > res = read(fd,buf,sizeof(buf)); /* returns after sizeof(buf) chars have been inputed or timeoutt */
> > >
> > >
> > > STOP=TRUE;
> > > }
> > > buf[res]=NULL; /* so we can printf... */
> >
> > that looks suspect to me, I forget what the spec says NULL means in that
> > case, but I'd use '\0' or just 0 instead, but what you do may work. I
> > also suspect that if read reads sizeof(buf) bytes and then you set
> > buf[sizeof(buf)] = 0 you will possibly touch memory that isn't yours.
> >
> > Trev
> >
> >
> > > /*That makes sure there is a null to form a strint.*/
> > > /*printf("%s\n", buf); */
> > > return;
> > > } /*Receive incoming serial data.*/
> > >
> > > The only thing I can adjust in the port setup is a
> > > variable that is either kept at 0 so it will time out if no
> > > characters are received at all or to, say, 1024 or whatever the
> > > buffer is defined as. This really doesn't effect the issue but
> > > if set to > 0, the timeout never happens until at least one
> > > character is received.
> > >
> > > Here is the initialization routine. Hardware flow
> > > control is not an option as the receiver does not recognize
> > > RTS/CTS.
> > >
> > > #include "headers.h"
> > > #include "defs.h"
> > > #include "externs.h"
> > >
> > >
> > > void portinit()
> > > {
> > > struct termios oldtio,newtio;
> > >
> > > fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY );
> > >
> > > if (fd <0) {perror(MODEMDEVICE); exit(-1); }
> > >
> > > tcgetattr(fd,&oldtio); /* save current port settings */
> > >
> > > /*Clear everything about that port.*/
> > > bzero(&newtio, sizeof(newtio));
> > >
> > > newtio.c_cflag = BAUDRATE | CS8 | CLOCAL | CREAD;
> > >
> > > newtio.c_iflag = IGNPAR | ICRNL;
> > >
> > > newtio.c_oflag &= ~OPOST;
> > >
> > >
> > > /* set input mode (non-canonical, no echo,...) */
> > >
> > > newtio.c_lflag = 0;
> > >
> > > newtio.c_cc[VTIME] = 20; /* inter-character timer .1 seconds/tick */
> > > newtio.c_cc[VMIN] = 0; /*Blocks until VMIN chars or timeout.*/
> > >
> > >
> > > tcflush(fd, TCIFLUSH);
> > >
> > > tcsetattr(fd,TCSANOW,&newtio);
> > >
> > > return;
> > > }
> > >
> > > I have tried tcflush at the end of a receive with absolutely no
> > > effect on anything.
> > > Shane W writes:
> > > > Hmm, reading from the ttySx device should never give
> > > > duplicatedcharacters so it sounds like something is up with
> > > > your buffer. I wouldn't zero it out but just keep note of
> > > > the number of bytes read and when to stop. Also, after your
> > > > first read returns, don't sleep but rather call poll() on
> > > > the device which will return when there is data ready to be
> > > > read.
> > >
> > > Yes. It is like it is already ready to receive data too
> > > early.
> > >
> > > The hardware is a USB-based 8-port adaptor which behaves
> > > quite normally when using Kermit or other serial routines.
> > >
> > > Thanks.
> > >
> > > _______________________________________________
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>
>
>
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