Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!ucbvax!CC.SFU.CA!Ray_Davison
From: Ray_Davison@CC.SFU.CA
Newsgroups: comp.protocols.appletalk
Subject: Re: Asynchronous Serial LaserWriter Driver?
Message-ID: <2394515@cc.sfu.ca>
Date: 13 Jul 90 21:28:34 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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I, too, had a need for a Serial LaserWriter Driver. In my case it was
to connect a Mac+ to a NeXT to use the NeXT printer from the Mac 
without resorting to the expense of Ethernet for a single connection.
I solved the problem by modifying the laserwriter driver to make it
do what I wanted. I have since learned that there is a serial version
of a laserwriter driver available from APDA or some such. I have also
heard that it may not be very good, and my mods serve my purpose.
Because I made the changes for a very specific purpose, my mods may not
work for you. Also, because there were a number of people I knew who also
had a Mac and a NeXT, I wrote an article for a local NeXT newsletter. The
newsletter is in WriteNow so you will need a NeXT to look at it, but if
you have one, you can get a copy via anonymous FTP from cs.ubc.ca
(128.189.97.5) in the file next/NeXTVieW/Issue01.tar.Z and look for the
article called "The NeXT as a Print Server for a Macintosh". For those
who cannot get a copy of this article, I have reproduced below the part
of the article on modifying the driver.
 
Modifying the Mac to print over a serial cable
 
We need a LaserWriter printer driver, since we want to produce PostScript
for the NeXT. The trick then is to start with this driver and modify it so
that it will send its output over the serial port to the NeXT. The following
instructions will require the use of a program called ResEdit, or some other
resource editor. Although the changes are fairly easy, failure to follow
the instructions carefully will render the driver inoperative. It is a good
idea to make a copy of the LaserWriter driver before beginning.
 
The first thing you need to change will cause the driver to act as though
you have pressed the command-f key and the driver will send its output to
a file (this will be fixed later to send the output to a serial port)
rather than to an AppleTalk connected LaserWriter. The change is in a 
resource called PDEF number 125. There are five changes to make, and the
location (address) of these changes is different depending on whether you
are using version 5.2 or version 6.0 of the driver. Table 1 shows the
location to change in each of the version, the current value at that 
location, and the value to change it to.
 
   +----------------------------------+
   &    Location     &        &       &
   &-----------------& From   & To    &
   &  V5.2  &  V6.0  &        &       &
   &--------+--------+--------+-------+
   &  B96   &  C78   & 57C0   & 51C0  &
   &  B9A   &  C7C   & 56C0   & 50C0  &
   &  BA2   &  C84   & 57C0   & 50C0  & *
   &  BAA   &  C8C   & 57C1   & 51C1  & *
   &  BB8   &  C9A   & 57C1   & 50C1  &
   +--------+--------+--------+-------+
                  Table 1
 
The next change is to jump over the code that creates the file, and a few
other things to do with writing the output to a file. Since you are going
to send the output to a serial port you don't need this code. Table 2 
contains the information to be changed, again in PDEF 125.
 
   +----------------------------------------+
   &    Location     &              &       &
   &-----------------& From         & To    &
   &  V5.2  &  V6.0  &              &       &
   &--------+--------+--------------+-------+
   &  D96   &  E9E   & 554F (V5.2)  & 6038  &
   &        &        & 558F (V6.0)  &       &
   &        &        &              &       &
   &  142C  &  1860  & 660C         & 600C  &
   +--------+--------+--------------+-------+
                  Table 2
 
Now you have just two more changes to make. The first will get the driver
to write its output to a serial port. The resource STR number -8191
contains the name of the file that the driver will write its output to. 
It is currently "PostScript". Change this string to ".BOut". This will
cause the output to be sent to the printer port. If you would rather use
the modem port, change the string to ".AOut".
 
The final change is a cosmetic one. The resource STR number -8159 contains
a message that is displayed while sending the output to the file (now the
serial port). It currently contains the message "Creating PostScript File".
This can be changed to something like "Sending print file to NeXT".
 
Once this is done, you can quit ResEdit (saving the changes before you do)
and place the new driver file in the System Folder. You might want to change
the name of the driver file to something like "NeXT Printer" so that it
will not be confused with an unmodified printer driver.
 
One important point in using the new driver. It is important that AppleTalk
be inactive if you are using the printer port. However, when you select the
driver from Chooser (which you must do before you can use it), a message
will come up on the screen claiming that the printer requires AppleTalk.
This is not true, but when you click on OK, chooser will set the AppleTalk
active button. Before you quit Chooser you must click on the Inactive
button for AppleTalk. Another message will come up asking you to make sure
that the AppleTalk network is disconnected. You can then click on Continue
and quit Chooser. The Macintosh side of things is now finished.
 
That is the end of the piece of the article. If this sounds like it may 
work for you, by all means use it. One other note. If you want to make
the driver send the LaserPrep file (like you get when you hold down 
command-k) then change the two locations marked with * in table 1 to
"51C0" and "50C1" rather than "50C0" and "51C1".
 
Hope this helps.
Ray_Davison@cc.sfu.ca