Character LCD module grayscale display

Infineon / Mitsubishi / Fuji / Semikron / Eupec / IXYS

Character LCD module grayscale display

Posted Date: 2024-02-03

It is a convenient and popular display device in electronic work. The display of this kind of LCD module only has 2 grayscale dot matrix ON/OFF, and there is nothing that can display multiple grayscales. However, with a little ingenuity in how you use these LCD modules, you can use gradient displays to add various attributes to boring character LCDs.

Grayscale display mode

frame sequence

As explained in the STN LCD panel demo, the grayscale display of the STN LCD monitor is performed by frame-by-frame point ON/OFF ratio control (so-called PWM). Since the response of STN liquid crystal is slow, ON/OFF is displayed in average concentration. Graphical LCD controllers handle this problem (3D jitter) in hardware.

The character LCD display module is also an STN LCD or TN LCD, and should also be able to display grayscale. However, the HD44780 does not have this grayscale display function, so it requires software to rewrite the display to achieve it.

In the experiment, as shown on the right, we added gray levels (4 gray levels) to the display by rewriting the display in a sequence of 3 frames for each frame. If you do not adjust the rewriting timing according to the LCD frame timing, you will not be able to obtain a clear grayscale display. Even simpler labeling in the background of an active item in a two-frame sequence is expected to yield a satisfactory display.

#Character #LCD #module #grayscale #display