Q: Lcd Contrast And Pwm

[Chris]

Ok so it seems powertip's PG12864 serise of lcd's run at -5v to +5 for
contrast

how can i generate a range of -5 to +5 with pwm? i can do -5->0 ot 0->5
but how can i do the whole range?

or what would be the best way to have software controlled contrast?

Thanks