laser-lovers@uw-beaver (01/26/85)
From: jp@LANL (James Potter)
I think that I know how to add the ability to do 300 dpi
graphics (full page) on the hp LaserJet. I would guess
that there might be others interested in this possibility.
Basically what is needed is a 1 Mbyte RAM which can be loaded
with the desired bit image. Then, one needs to get a byte loaded
into a shift register every 4 microseconds or so. Everytime the
printer puts out a horizontal sync pulse, one begins loading and
shifting the data (after the appropriate beginning of line delay).
The output of the shift register would be or'ed with the normal
LaserJet data stream so that the bit image is superimposed on whatever
text or other graphics the LaserJet is ready to print.
All that is needed besides the memory is some way of loading it,
perhaps a micro that will take vector draw commands, etc over a serial
input and convert them to set bit in the memory. I think it will be
relatively easy to access the data at 4 microsecs per byte, especially
since there is a delay after each horizontal sync pulse that should
allow setting up a pointer to the beginning of the data for the next
line. Only problem I see is that if the 1 Mbyte memory is windowed
onto a 12 bit or so address space some care must be taken to ensure
that data for a line doesn't cross a 'page' boundary.
I would be interested in hearing from anyone who would like to
use such a development and from anyone who would like to contribute
their ideas (or other help) to the project.
Jim Potter jp@lanl.ARPA