serial H/W flow control -- a fairy tale?

[Jerry Feldman]

On Sat, 15 Sep 2007 16:04:28 -0400
"R. Luoma" <nobluspam5476-MTb9uo0rH9eJIAd+swBSYQ at public.gmane.org> wrote:

> the fairy tale:
>=20
> Once upon a time, two computers were communicating with each other
> over their RS-232 serial ports.  During the data transfer, when
> the receiving system's UART FIFO was getting full, it would use
> the hardware RTS/CTS line to tell the other system to stop
> sending data until the receiving system had a chance to empty
> the FIFO.  The magical UART would handle in hardware all the messy
> details.  No data would be lost and birds would bloom and the flowers chi=
rp.
>=20
> In reality, I am getting many over-run errors because the transmit systems
> keeps merrily sending data whether the receiving system's UART FIFO is fu=
ll or not;
> furthermore, the after the FIFO fills, the RTS/CTS never change;
> I have set the CRTSCTS flag, but there seems to be no hardware flow contr=
ol at all.
>=20
> Am I missing something?
> Is serial flow control just an internet fairy tale?
>=20
> Under linux, are there program to whether hardware flow control works?
> If so, where can I find these programs?

Check the pinouts first. I've found that many RS232 (9 or 25 pin)
jacks don't actually have those pins connected. Check the cable too.
The stty and setserial commands should be able to set the appropriate
characteristics. Additionally, the serial driver also needs to be able
to set these things.=20
--=20
Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org>
Boston Linux and Unix user group
http://www.blu.org PGP key id:C5061EA9
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