Graphic LCD modules for gpsim

Directories:

src/      -- source code for gpsim module
examples/ -- PIC assembly code illustrating the module.
utils/    -- Utility for converting PNG files into gpasm include files.
doc/      -- Manufacturer data sheets

The graphic LCD module is a gpsim module that simulates a Varitronix
100 X 32 pixel graphic LCD. The graphics controller is a Seiko
SED1520. Data sheets for the module and controller can be found in the
doc/ subdirectory. The real display can be purchased from Mouser.

(BTW, the Varitronix "data sheet" leaves much to be
desired. Fortunately (for you) I've taken the time to understand how
the real module behaves and wrote the simulation to mimic the actual
device. The only (major) thing not supported at the moment is the LCD
contrast. If you're using a real display, you'll need a negative
supply of -1.0 to -2.0 volts tied to the "V0" pin. A relatively simple
way to generate this is with a diode/resistor/capacitor voltage
inverter driven from an oscillating I/O pin:

                  C1       D2
  PIC I/O  -------||---+---|<---+---------+
               0.01uF  |        |         \
                       V D1    === C2     /<------ V0 contrast
                       -        | 0.01uF  \  100K pot
                       |        |         / 
                      ///      ///        |
                                         ///

None of the values are too critical. However, you may wish to add an
addition resistor between D2 and the potentiometer just to protect the
display against overdriving. 

This circuit is a classic negative voltage generator. When the PIC I/O
is high, C1 charges through D1 to Vdd-0.7 volts. When the PIC I/O line
drives low, D1 becomes reversed biased and C1 discharges though
D2. The direction of the current is such that C2 becomes negatively
charged. The potentiometer divides this negative voltage by a user
selectable amount to created the LCD bias.)



Installing:
----------

See INSTALL for directions on installing the graphic LCD module. Also,
there are directions for running the example.


BUGS:
-----

Module Update - the graphic module doesn't automatically update
itself.

gtk-2.6 segv - the graphic module doesn't run in pre-gtk-2.8.

