Chinese math?

[John B]

I ordered a graphics and receiveda a 4 line text LCD.
Decided to keep the 4 line text, got it for half the price,
and now also have the graphics.
Hooked up the 4 line text LCD, could not figure out how to address
line 3. So made a slow loop that printed the RAM address while
filling up RAM.

So just observed where it started:

#define LINE_1 D'128'
#define LINE_2 D'168'
#define LINE_3 D'148'
#define LINE_4 D'212'

Logic?

Those are the standard starting addresses for the HD44780 controller.
There's a lot of stuff out there Gluegun gets 70k hits. Here's the data
sheet:

http/www.sparkfun.com/datasheets/LCD/HD44780.pdf