Re: tcdrain / TCSBRK / wait_until_sent delay

[Andy Parkins <andyparkins@gmail.com>]

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On Monday 2005 May 09 10:22, Christer Weinigel wrote:
> Christer Weinigel <christer@weinigel.se> writes:
> >     do {
> >         ioctl(fd, TIOCSERGETLSR, &lsr);
> >     } while (lsr & TIOCSER_TEMT);

In case you are interested, I found another problem (but this time a solution 
too); my code is now (edited for brevity):

	do {
		ioctl(fd, TIOCSERGETLSR, &i);
	} while( !i & TIOCSER_TEMT );
	tcdrain( fd );

The tcdrain() at the bottom returns fast (presumably because the transmit 
buffer is already empty) so the original problem is solved.  Without the 
tcdrain() the port is left in a strange state - at random, future writes are 
silently dropped.  The echo back when this happens is simply a NUL.  With the 
tcdrain() in place, that problem goes away as well.

Andy


-- 
Dr Andrew Parkins, M Eng (hons), AMIEE


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