
How to write Uniprint files.

  or The Ignorant Man's Guide to Weaving

Disclaimer: This is not yet a How-To, not even a mini-How-To. But if
I can manage to keep trying and get some work put into it, and if we
have less atmospheric electrical activity than we have recently, it
just might grow up to be one.

First off, this information came about because the Epson 740 met the
price-performance ratio I was looking for, and I ASSUMED that since
the ESC 600 and ESC 800 were supported, the ESC 740 would be, too.

Wrong!

So I guess it was up to me. A few evenings with some scratch paper,
and then some time on the plane to and from the 1999 International
Solid State Circuits Conference in San Francisco, (from Vermont) and
I had an Epson 740 functioning under Linux.

This work came from examining the upp files that came for the ESC
600 and 800, sort of figuring out what they were up to, and then
trying to do the same thing for the 740. So without all of the
original Uniprint work by <insert name here>, this never would have
even left the ground.

A Few Words About Weaving

The Epson Stylus Color printers have some number of inkjets, which
varies from model to model. Unfortunately, all models have jet
pitches which are significantly coarser than the desired resolution.
(Except for the ESC 900, which I don't know how to make print at
360*360.) As a result, printing is a combination between stepping
the paper in some appropriate pattern, and using the appropriate
ink jets.

I have worked with three examples, the 600, 740, and 800. To begin
with, let's consider 720*720 resolution. The 600 does this in 8
passes. That means that the jet pitch in the print head is 8 times
coarser than the dot pitch, or 90 jets/inch. At that same resolut-
ion, the 740 takes 6 passes, or 120 jets/inch and the 800 takes
4 passes, or 180 jets/inch. I have reason to believe that the new
ESC 900 will take 3 passes, or 180 jets/inch.

One way to weave this would be to paint a row, step 1/720 inch,
paint the next row, etc, until 8 rows are done, using the 600
for reference. After this, one would step past all that has been
printed and begin the next swath. The problem with this scheme
is that each head would be printing 8 adjacent rows. If one jet
was undersized, there would be fine white lines visible between
the printed rows. If a jet was oversized, there would be dark
lines.

Microweaving

It's much better if adjacent rows were never printed by the same
jet. That way, things would average out better.

