[Coco] Re: Coco printer primer...

Brian Blake random_rodder at yahoo.com
Wed Feb 15 18:16:09 EST 2006

Torsten Dittel <Torsten at Dittel.info> wrote:  > I have access to an Okidata 320T (OS compatible down to MS DOS, and emulates IBM ProPrinter III, Epson Fx-80, ANSI and Oki Microline) with a RS-232C serial adapter that works great. Would making a serial cable to work with the 'bit banger' port (do not have a RS-232c cart yet) be difficult? I know on a PC this wouldn't be a problem, but, using the four pins from the b/b port to a 25 pin sounds too easy of a solution...

Well, the signal levels of RS-232 (logical "one" is between -12V and
-3V, "zero" between +3V and +12V) are different from what's on the
bitbanger port (0V or 5V). Normally you'd need a small circuit with it's
own power supply which contains a MAX232 compatible IC which will adapt
the CoCo's levels to the standard. However, some printers might accept
the CoCo's signals and I'm sure there's a workaround without too much
hardware efforts. Another question is if you have real CTS/RTS hardware
handshake or XON/XOFF protocol software handshake.


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The additional circuit makes a lot of sense in that regard. Back in the early-mid 80's, when I had my first Coco, I distinctly remember using only a cable between my Coco and the Okidata 82A printer. I cannot recall if it was serial or parallel, though I'm almost willing to bet it was parallel as I remember thinking how goofy looking the Centronics connector looked. Hindsight makes me wish I hadn't sold it all back in '91 (Coco1 & 3, modem, printer, 6 floppy drives and literally hundreds of floppy disks full of programs). I sold it all at a yardsale in Chicago. 
  That cable would answer a lot of questions. 
  I know the Coco, printer and all accessories were purchased from Computers Plus in 1982. Considering I was 14, I'm glad to remember that much (that and I just wasn't into computers, etc. as much as I am now). 
  Thanks much for the info. Learning more with every reply.

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