by Kevin Wormingto » Fri, 27 Feb 1998 04:00:00
I am very new to serial programming, so please forgive me if this is a
simple question. I want to be able to detect DCD on a multi-port serial
line that does not support TIOCMIWAIT. Is there any other method I can use
to cause portslave to "wait" for DCD from the modem?? The general idea is
to set the modem for auto-answer and have portslave wait for DCD from the
modem to begin the login/ppp process.
Please reply via e-mail as well as usenet.
Thanks in advance
Kevin
1. How to detect DCD on serial port
Hi ! .. I was trying to make some software for my computer ...
What I want is :
It is "SUPOSSED" that if I try and OPEN on a serial port and there is
NO DATA CARRIER DETECT (DCD), the OPEN rutine MUST BLOCK until DCD is UP .
RIGHT ??? So when the electricity goes off I can sense it, then make DCD UP
in the serial port and then shutdown my machine before my UPS goes off
... easy isn't ?
Well I'm programming on a NeXT (OS 2.0) the manual (zs) says :
When /dev/ttyda is opened, the device driver
asserts DTR and then blocks waiting for the
modem to assert DCD
OK ?
So I was using /dev/ttyda and then make an open call BUt it returns
inmediately !!! and there is nothing in the serial port A.
Well this is my first problem ... is there a way to make this posible ??
Another solution may be to open the port and then make a call to get some
paremeters, maybe DCD as says <sys/ioctl> :
#define TIOCM_CAR 0100 /* carrier detect */
So anybody out there knows how to get this parameter ?
or how to make the OPEN call to blocks ??
Many thanks in advance !!
___________________________________________________________________________
Jose Angel Vela Avila.
Instituto Tecnologico y de Estudios Superiores de Monterrey
I.T.E.S.M
Mexico.
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