tty000 troubles w/modem

DoN Nichols dnichols at
Mon Apr 29 06:48:23 AEST 1991

In article <28248 at uflorida.cis.ufl.EDU> ruck at (John Ruckstuhl) writes:
>I've freshly installed 3.51m and HDB on a 3b1 with a US Robotics 
>Password 1200 baud modem on tty000.  The Password uses a subset of the
>Hayes AT command set, and powers up in a no-echo mode (the command ATE1
>will start the command echoing, and then it looks much like a Hayes).

	[ ... ]

>Some System Administration guides suggest that one ought to be able to
>do things like 
>    echo "A" > /dev/tty000
>but here, even root can't do that -- you hang, (working), until you
>break out of it, then you get the error message:  
>    /dev/tty000: cannot create
>Or at least, I do.

	Sounds as though your problem is that the older version didn't pay
attention to DTR, and the newer one does.  (Does the robotics machine have a
DTR light?  Is it out when you are unsucessfully attempting a connection?
If so, do you have either a hardware switch or a software switch to either
make it hold DTR true forever, or preferably to drop DTR momentarily, then
restore on loss of carrier.

	Since it works just after power-up, you might try sending the
reset string 'AT Z' during the cleanup after a call, (while you still have
its attention - that is before the other system drops carrier.)

	I seem to remember mention of an alternate minor device number which
allows access while ignoring the DTR signal.  If I remember correctly, you
add 128 to the minor device number of your port, and mknod a new device with
that.  That device ignores DTR.  (I don't remember whether that was in this
group, but for my newly acquired sun-2, it is documented, and is used for
outgoing calls, while the other is used for incoming calls.  When one is
opened, the other cannot be opened, thus preventing an outgoing call attempt
from disrupting an incoming one.  (As I say, I don't know for sure whether
this works on the 7300/3b1.)

	There is an excellent set of help files for HDB on osu-cis --
somewhere.  (I don't know where it landed after the reorg.)  While it was
mostly aimed at Trailblazers, it will probably help you, as well.

	Good Luck
Donald Nichols (DoN.)		| Voice (Days):	(703) 664-1585
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