NetNews Usenet Archive 1992 #19/NN_1992_19.iso/spool/comp/sys/3b1/3205

Internet Message Format | 1992-08-25 | 3.5 KB

Path: sparky!uunet!beartrk!ceilidh!hijo-2!dnichols
From: [e-mail] (Don Nichols (DoN.))
Newsgroups: comp.sys.3b1
Subject: Re: netfax (was: Re: 3b1 internal modem-flow control)
Message-ID: <[e-mail]>
Date: 25 Aug 92 21:36:09 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Organization: D and D Data, Vienna Virginia
Lines: 57

In article <[e-mail]> [e-mail] (Boyd Ostroff) writes:
>In article <[e-mail]> [e-mail] writes:
>>
>>I have gotten a copy of the netfax software (from ftp.uu.net),
>>and started trying to see if I could get it running.
>>
>>Anybody else working on this?
>
>I have a Mac connected to my 3B1 through the serial port, and the
>Supra v.32bis FaxModem also hooked up to a 3B1 port.  I was going to write
>a simple program that would open both ports for r/w so the Mac would
>"think" it was just talking directly to the modem.  Do you think that would
>let the Mac fax software work with the modem?

    First, be sure to put both ports in 'raw' mode.  (I forget what the
ioctls are for that, but you should be able to find it in the
/usr/include/sts/termio.h.

    Second, if you are planning on running at 19200 baud, remember the
discussion that we have been having here recently, and expect characters to
be dropped.  You can have some lost with long streams of data with only the
interrupt load of a single RS-232 port.  It will be twice the interrupt load
here, and I would expect there to be a fairly long data stream from a fax.
(I don't know what size packets they are useing, nor how often they need
acks to keep the flow going, but I would expect trouble.)  If the faxmodem
can handle 9600, you probably would get better reliability.  (I also don't
know if the two ends can be at different rates with faxmodems.)

    If you don't need to make this automatic, you might just install a
RS-232 switch box so you can manually transfer from one machine to the
other.  (This puts the burden on you to check that uucico isn't doing
something with the modem - or about to do so, and already has it locked.)

    If you want to make it automatic, but not load down the 3b1 to this
extent, or need the speed that would crash the 3b1, then you might set up a
T-bar relay under program control to switch which machine gets the modem at
a given time.  (The T-bar relay can switch 24 circuits at once in not too
big a space.)  Since you have 25 pins on your RS-232 connector, you may be
wondering which pins not to switch.  Of course, you don't need all the pins
anyway, but I would absolutely *NOT* switch pin 1.  That is the safety
ground, and should be tied together in all machines in the interests of
preventing zaps to drivers when you switch.

    If you do feed it through your 3B1, you'll need to set the software
up to to that checking and refuse a connection to the modem if it is being
used by the system.  (The lockfiles in /usr/spool/uucp.)  Also, if you are
using the modem for dial-in to the 3b1, you'll have to turn off the getty on
that port before the call out, or the program and getty/login will be
fighting for characters.

    Good Luck
        DoN.
--
Donald Nichols (DoN.)     | Voice (Days): [phone] (Eves): [phone]
D&D Data                  |  Email: <[e-mail]>
I said it - no one else   |         <[e-mail]>
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