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Re: tcflush hang problem
- From: Brian Ford <ford at vss dot fsi dot com>
- To: cygwin at cygwin dot com
- Date: Mon, 13 Oct 2003 14:56:22 -0500 (CDT)
- Subject: Re: tcflush hang problem
Sorry, my fingers aren't working. I keep accidentally replying to the
sender rather than/in addition to the list.
Cygwin's current tcflush implimentation is rather crude. Although, it may
not be possible to do any better. PTC.
if (queue == TCIFLUSH || queue == TCIOFLUSH)
/* Input flushing by polling until nothing turns up
(we stop after 1000 chars anyway) */
for (int max = 1000; max > 0; max--)
if (!PurgeComm (get_handle (), PURGE_RXABORT | PURGE_RXCLEAR))
if (!ClearCommError (get_handle (), &ev, &st) || !st.cbInQue)
So, your not really hung. Just stuck for a long time.
As a work around, tell the device to shut up first, then flush.
On Mon, 13 Oct 2003, Martin Farnik wrote:
> I use CYGWIN_98-4.10 mine 1.5.5(0.94/3/2) 2003-09-20 16:31 i686 uknown
> unknown Cygwin
> First i try to describe a situation:
> I have a device which is connected with computer thru serial line.
> Device is still sending data.These data isn't for my program.I have
> open com port and let them go into buffer . When a want to talk with
> device i flush input buffer, send it a command paket and device stop
> sending data and wait for my next command.
> Problem is when I want to flush INPUT buffer before I send a command. In
> this point it hangs, maybe for buffer full.
> Here is piece of code:
> -----I open port when i start program -----
> fd = open(PORT0, O_RDWR | O_NOCTTY );
> tcgetattr(fd,&oldtio); /* save current port settings */
> bzero(&newtio, sizeof(newtio));
> newtio.c_cflag = CS8 | CLOCAL | CREAD | CSTOPB;
> newtio.c_iflag = 0;
> newtio.c_oflag &= ~OPOST;
> newtio.c_lflag = 0;
> newtio.c_cc[VTIME] = 1;
> newtio.c_cc[VMIN] = 0;
> tcflush(fd, TCIFLUSH);
> --this code is execute when a want to talk with device----
> tcflush(fd, TCIFLUSH); <--------- in this point where it hangs
> err = write (fd,iobuffer,10);
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
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