I am using /dev/ttyS<n>.
Both machines have 16550A uarts.
I use tcdrain before deasserting RTS.
My understanding of CRTSCTS is that the DCE device uses CTS to start and
stop the DTE device Tx to prevent buffer overrun. My DCE device won't
grant CTS if it can't receive but expects the DTE to drop RTS to signal
end of message.
The symptoms on the Dell laptop are:
I successfully deassert RTS in initialization. I do this since RTS goes
high on open of the serial device. When I try to assert RTS nothing
happens. The application thinks all is ok and procedes to wait for CTS.
I'm not familiar with TIOCSERGETLSR but will look into it.
Thanks,
john
[EMAIL PROTECTED] wrote:
>
> I am still using SlackHat with 2.0.38 and retrofits, so I can't comment
> on 2.2.x, except I don't think /dev/cua<n> is supported anymore. You
> should be right if you use /dev/ttyS<n>.
>
> I don't see anything wrong about using TIOCMGET/TIOCMSET. CRTSCTS would
> do the same automagically, but it makes some requirements about the
> other signals that might greatly inconvenience you. Depending on the
> size of the FIFO in the UART, you might need to read the LSR with
> TIOCSERGETLSR to check that all characters have gone out on the line
> before you drop RTS. I'm pretty sure write() won't block on that, so if
> the box that works has a 16450, and the one that doesn't has a 16550A,
> that may well be the trouble.
>
> It would help if you told us _how_ it doesn't work (symptoms, please :-)
>
> Lawson
> >< Microsoft free environment
>
> This mail client runs on Wine. Your mileage may vary.
>
> On Wed, 13 Oct 1999, John Florence wrote:
>
> > I have an application that needs the ability to assert RTS before
> > sending a 700 bit message and to deassert RTS after CTS is granted and
> > the message is transmitted. I use ioctls and TIOCMGET/TIOCMSET to
> > control RTS. The application seemed to run fine on a Compaq running an
> > old version on Slackware (kernel 1.2.8) but won't run on a Dell laptop
> > running Red Hat 6.0. I looked at the serial device driver in the
> > Slackware and the Red Hat systems and they are the same.
> >
> > Has anyone else had problems with Red Hat, kernel 2.2.5-15, and/or
> > laptops? Comments on my technique are also welcome - I know that I
> > should write a device driver but for now I'm just trying to get
> > something working.
> > --
> >
> ------------------------------------------------------------------------
> > John Florence, Mathematician, VSS Group, 25-162 Phone:
> 240-228-6685
> > JHU/APL, Johns Hopkins Road, Laurel, MD 20723 FAX:
> 240-228-6663
> >
> [EMAIL PROTECTED]
> >
> > -
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> in
> > the body of a message to [EMAIL PROTECTED]
> >
>
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--
------------------------------------------------------------------------
John Florence, Mathematician, VSS Group, 25-162 Phone: 240-228-6685
JHU/APL, Johns Hopkins Road, Laurel, MD 20723 FAX: 240-228-6663
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