Thread: So many HD44780 wiring schemes! Which one to use?

There was a wrong schematic going around for the 4 line displays.

The pins were reversed on a couple of pins to the parallel port for the 2nd set of lines.

If you look at a schematic for a 2 line display, and compare it to a 4 line display, you can see you just add a couple of wires.

Look at the description of what the parallel port shows (input output etc) of the 2 line schematic. Now just match those descriptions to the 4 line schematic, and you should be able to see which ones were reversed.

On mine pins 14 and 16 of the parallel port needed to be swapped. RS and R/W on the LCD driver.

I don't know if any schematics were drawn correctly for the 4 line.

The safe bet is to compair your spec sheet with the schematic.

Good luck, it isn't that hard.

(just double check the power)