afo@i.cc.purdue.edu (Alan Davis) (10/26/86)
HELP PLEASE!!
I just bought an Atari 1040 ST and hooked up my ancient
Epson MX100. Everything works fine on it (1st Word, print
files) but when I press ALT-HELP to dump the screen, I get
strange results. It prints the graphics ok, but for each
line of graphics it also prints 3 blank lines in between.
Can somebody give me a clue as to what I need to do. I've
configured the "install printer" accessory correctly (not
much choice in that) and I've set the dipswitch 2-3 to "on"
instead of off. The switches were the same as from factory
otherwise but that still doesn't help. And as some may know,
the manual for this printer is far from good.
Can anyone help me. How about Neil? How about Epson? Are you
listening/watching?
Thanks in advance,
Alan Davis
Purdue University Computing Center
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Disclaimer: My boss has opinions too but I can't express them in public.
Therefore, I thought up my opinions all by myself.katzung@iwtpu.UUCP (Brian Katzung) (11/01/86)
[Pacman lives]
Sounds familiar... I bought my atari, soldered up a parallel cable for my
old OKIData Microline 92 which was formerly speaking RS232 serial, tried to
print some things, swore a little, flipped some option settings, etc. After
I got the basics to go, I tried a screen dump and got the same results as you
did (looks like blank bands between each print pass).
I didn't have a better way to view the control stream, so I put the
printer in low-res mode for 480 bytes but gave it no data, and then started
a screen dump. Decoding the pixel patterns, I found the following ugly
sequence at the end of the first line of graphics data (I don't know about
the other lines, but I assume they're the same; they *LOOK* the same):
ESC '3' 1 (theoretically, advance in 1/216" increments)
LF (OKI/Epson stepper can only step 1/144", so does 1/144")
ESC '3' 1 (beats me why they do it again)
LF (another 1/216" (IBM) or 1/144" (OKI/Epson))
LF (and another)
ESC '1' (set 7/72" mode)
LF (travel 7/72" (everybody))
(The 7/72" mode is correct, but I'm working from memory on the ESC '1'
code, so that might not be the correct character sequence.)
This whole mess is supposed to advance the 8/72" height of the print head.
The stepper motors for the OkiData (and, I guess, the Epson series) step
in 1/144" steps instead of 1/216", so the printer goes 1/144" on a 1/216"
request to avoid the problems of not spacing at all. The problem is
that after three 1/144" steps, we've gone 1/144" beyond 3/216" (1/72").
The printer corrects advances of 3/216" steps to 2/144", but it doesn't
have the smarts to correct them when they come 1 or 2/216" at a time.
If the 1/216" section had been replaced with
ESC '3' 3
LF
the problem would not have shown up (at least in screen dumps).
I have a call in to Atari to see if they already have a simple solution to
this (besides buying an IBM printer). If not, I wrote an algorithm to
correct accumulative and local error on the fly. If Atari doesn't have
an easy answer, I will also write the code to insert my algorithm between
the BIOS trap vector and the lst: output routine (it's an ugly scheme, but
what can you do when your *OS is in ROM?).
Anyone who is interested in the results should send me mail. If I get a
large response, I'll post them.
-- Brian Katzung (ihnp4!{laidbak,iwtpu}!katzung)