[Coco] Printing from DW

[Gene Heskett]

On Tuesday 28 October 2014 07:52:02 Francis Swygert did opine
And Gene did reply:
> Date: Mon, 27 Oct 2014 11:35:47 -0400
> From: Al Hartman <alhartman6 at optonline.net>
> 
> In "Turn of the Screw" there is a Parallel Port Cartridge.
> 
> If someone made up the board for it, I'd love to build a couple.
> 
> Couldn't an OS9/NitrOS9 driver be written for it, and then the printing
> problem would be solved.

It already has been, via drivewire & nitros9 at least, and it works a 
treat.

However, and as I have related several times in the past, all of these 
hardware designs have to date, simply presented the data, and the data 
strobe, to the printer at the coco's native cpu speeds.  That means the 
data and strobe is only valid for 1/2 an E-Clock cycle.  When you tie a 
printer, with the FCC/DOC required noise filtering at its inputs, this is 
about 4x faster than the printer can read it reliably so it skips 
characters and make mistakes.

To not repeat myself forever on this, see my previous msg on this subject 
within the past week.  There MUST BE a buffer between that port and the 
printer that will hold this data stable for 3 or 4 microseconds at 
minimum. To put a point on the use of the halt line to control by stopping 
the cpu while the strobe is active, you have a lockup forever loop if the 
circuit does not include a timer to release the halt line, or the halt is 
cleared by the printers ACK strobe coming back.

But my point at the top of this reply is that a $100 Brother B&W laser 
printer, fed by the dw server host, give beautiful easily read output with 
zero character ambiguity between a one and an ell, and does it at 19 pages 
a minute!

The technology of printers moves on and you cannot stop it, so use the 
force Luke.  Or be prepared to design and build a parport interface that 
is specific for printers that does latch and hold the data for long enough 
that the printer can grab it without making any mistakes.

But don't expect to get rich off of selling them despite the willingness 
of some to pay a high enough price that the maker actually profits a few 
dollars by the time he has made and sold 25 of them.  Frankly, I'd feel 
guilty doing such, primarily because your old DMP's and Gorilla's that you 
would so gleefully extract from whatever storage space, buy the proper 
adapter and hook it up, only then to realize that there are not now in the 
marketplace, a suitable supply of both fresh (only if you define fresh as 
less than 20 years old) ribbons AND paper. In case you haven't noticed, 
even a box of tractor feed paper is only stocked one deep, and has a layer 
of dust on it at Staples.  So you would have spent the money for an 
interface as if you had thrown it out the car window, getting nothing 
usable for the $ spent.

I'd do it, but I am not built to screw my friends on this list in that 
manner.

I just built a print4dw.tar.gz of my /CoCo directory and put it on my web 
page in Genes-os9-stf.  That ought to lower the entry bar to doing it my 
way, at least on a linux box.

> He already provides patches for DECB.
> 
> =============================================================
> 
> I have an even better idea... maybe. Incorporate a parallel to USB chip
> in the cartridge. The only problem with that is there are few printers
> with built-in processors for fonts and graphics -- the computer does
> all that in modern USB printers. So it gets more complicated if you
> just want to plug in a printer and go. Use one of the micro
> controllers (Arduino?) to emulate a common printer (Epson something
> was compatible with all CoCo software) instead. That would work as a
> serial to USB printer as well, but with DW using the bit banger a
> cartridge might be a better solution.

I still think the archive mentioned above is a better solution once 
configured.  Heck, I could tell it to print to my color laser with a one 
line edit, but its toner tanks have less capacity and cost similar each to 
the one toner for the B&W laser.  And here, it Just Works(TM).

> 
> Frank Swygert
> Publisher, "American Motors Cars"
> Magazine (AMC)
> For all AMC enthusiasts
> www.amc-mag.com


Cheers, Gene Heskett
-- 
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