bperrybap:
I have looked at using serial mode in the past. It would be great to reduce the number of pins,
but as I recall, many of the displays, (and I believe this one as well), lose the ability
to read from the display when using their built in serial mode.
Currently the library code goes through many painful gyrations to avoid the use of a frame buffer.
It was a conscious decision to eat up additional flash space to avoid using much RAM
so that the library could function on all arduino boards including those like the m168 that
only have 1k of ram, which would never be able to support a frame buffer for a 128x64 display.
The current code can support any sized display up to 256x256 without using up any additional
RAM.
You are quite right, the ST7920 in serial mode doesn't let you read the data back. I was using a 128x64 glcd on an atmega328, and after experimenting with a partial buffer, I decided that in this application I could afford to use half the total RAM space for a frame buffer. I appreciate that this wouldn't always be an option.