🚀 go-pugleaf

In article <2068@dciem.UUCP>, frank@dciem.UUCP (Frank Evans) writes:
> I wish to hook a Mac+ to a cheap dot matrix printer! I have an old Radio Shack
> DMP 105 printer but I don't have the software driver ...

Frank,

     I wrote a simple desk accessory to allow my Mac 512 KE to print
text files on my Tandy DMP 110 dot-matrix printer.  I never made any
attempt to post or distribute it since I thought this to be a rather 
obscure combination.  The desk accessory was written in TML Pascal 
and was actually quite simple to write.  I will send you the stuff as
soon as I get it uploaded.  I am sending the source code, too.  
Even if you don't have TML Pascal, the code is so simple that it
would be easy to transport it to any language.

     The DMP 110 has a 4-pin DIN connector used for RS-232
communications to the Tandy Color Computer.  Presumably the DMP 105
has a similar connector.  Here are the connections that will work
with the 512, hopefully the numbers on the Mac+ serial connectors are
the same, although the plug is not.  Pin #1 is not used.  Pin #2 is
the "Printer Ready" line of the DMP 110, and goes to pin #7 on the
512 serial port.  This is equivalent to pin #20 on a standard RS-232
connector.  Pin #3 is the  ground, and goes to pins #3 and #8 on the
512.  Pin #4 is the data in pin, and goes to #5 on the 512.  I would
assume that the numbers on the Mac+ serial connector are the same,
but maybe not.  The same applies to the DMP 105 vs. 110, but you 
probably have a manual which will tell you for sure.

     The port I use on the DMP 110 operates at 1200 baud, and uses
a "hardware" (CTS) handshake.  This differs from the standard Mac
mode, which is 9600 baud and "software" (XON-XOFF) handshake.
This is fairly easy to get around if you write your own application
or desk accessory to print files, but means you can't really print
from within an application unless you want to write your own version
of the ImageWriter file (not likely, unless your masochism index is
quite high).  There is also a parallel port on the DMP 110, and 
I have heard that the circuit to accomplish serial->parallel com-
munications is easy to build, but I haven't had the time to 
investigate this.  If this port were used, the data rate would be
fast enough to support graphics, assuming you got around the format
conversion problem.

     There is one last thing to be aware of.  The DMP 110 uses a 
carriage return (13 decimal or 15 octal) to signal a return to 
column 1 AND a newline.  Apparently most computers, including the
Mac, assume that the printer will require both an carriage return
and a newline (10 decimal or 12 octal) to accomplish this.  If it
weren't for this difference, I could do all my printing using 
Microsoft Word and the Typewriter driver that comes with it.  (If
I try to print on the DMP 110 using Word, I always get double 
spacing because of the extra newline.)

     I am also posting this to comp.sys.mac.  If I get enough 
requests for it, I will post the driver.