Hacking the HD44780 16×2 character display for arbitrary pixel generation #Displays #ReverseEngineering @MisterHW

Many projects have used 16×2 character displays for output. They often include limited capability for special characters. Helge Wurst (@MisterHW) describes a potential way to drive HD44780-style 16×2 character LCDs in graphics mode by using a synchronized updating scheme and complementary special characters.

Although many controller manufacturers offer multiple CGROM variants (font sets) with special characters, there aren’t 2^40 different unique ones (128 GB) to display arbitrary 5×8 pixel blocks – needless to say the 40 bit character code might as well represent the pixel information itself.

If one could swap out a character before each line were serialized and sent to the column drivers however, each of 8 horizontal lines making up a 5×8 pixel character could be loaded from one of 32 characters. This subdivides the representation of an 5×8 arbitrary pixel block into 8 consecutively selected LUT characters.

See this GitHub page for the methodologies and code used.

See HD44780-based displays on Adafruit.


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