This application note describes how to implement automatic contrast
control of an LCD (liquid crystal display) using the MC68HC08LN56
microcontroller.
In applications where the power supply voltage can vary, such as in
battery-powered systems, maintaining a constant contrast on the LCD
display is desirable. This can be achieved in software on the
MC68HC08LN56 by using the A/D (analog-to-digital) converter in
conjunction with the LCD controller.
This application note discusses how factors such as the amount of
multiplexing, type of bias, and voltage levels can affect LCD contrast.
This is followed by a description of a system in which the A/D converter
on board the MC68HC708LN56 samples the system power supply and
the contrast control for the LCD is updated based on the result.
Also included here is the source code for implementing this system.