[plotter.txt 5/95 Digital Insight]

Using HP Plotters with UNIX

Here are some tips on using a plotter with Robochart. Equipment
varies, so there are no guarantees that everything here will work
on your system.


Handshaking

Plotters cannot usually keep up with even a slow serial connection,
so some form of handshaking between the plotter and the computer is
necessary to avoid overflowing the plotter's buffer. The preferred
method is to use hardware handshaking, where the DTR output (pin 20)
of the plotter is tied to the CTS input (pin 5) of the computer.
The alternative is to use software handshaking (XON/XOFF), which requires
the plotter's TX output (pin 2) to go to the computer's TX input (pin 3),
AND the appropriate command string to be sent to the plotter to enable 
XON/XOFF (the default HPGL header file $RCHT_DIR/rchart.plt includes
this command).


Printcap Database

To print to a serial printer, an appropriate entry is needed in the 
printer capabilities database /etc/printcap. Here is a starting point:

1|hp|HP Plotter:\
        :br#9600:ms=-parity,-tabs,onlcr,ixon,decctlq:\
        :mx#0:sh:\
        :lp=/dev/ttya:\
        :lf=/var/adm/hp-errs:

See man printcap and man stty for details.


Plotter Coordinates

Most plotters define the coordinate origin in the center of the plot
area, so this is the default assumption that Robochart makes. If your
plotter defines the origin at a corner of the plot area instead, you
may find your plots offset on the page (or partially off-page). You can
put the command "print HPGL corner" in your Robochart configuration 
file to fix this.

Also, Robochart assumes that A and A4 size plots are handled with the 
X axis along the long side of the paper, while largers sizes are done
with the X axis on the short side. If your plotter disagrees, try using
a plotter control button to rotate the coordinates, or adding a "RO90;"
command to the plot header file.