I found two DMC40218 (40 x 2 characters) amongst some old stuff and they work fine with LiquidCrystal() commands (they are dated 1986; 27 Y.O.!). The data sheet I found about this module (www.datasheet-pdf.com/datasheetdownload.php?id=535216 or pdf.datasheetcatalog.com/datasheets2/16/169708_1.pdf) mentions that it is HD44780 compatible (OKI M6222B-01 7Y26 controller in both), but I just could make it work only with 8-bit data bus, it does not respond to the 4-bit data bus' only configuration. I checked all connections and they seem fine, and I also changed the original code so it could handle the 40 characters and it ran OK, including a full-display scroll left and/or right. I actually tested the jig with at least four other different LCD modules, same Arduino UNO, and they all worked fine (the LCD's were 16 X 2 and I set the code correctly for 16 X 2 characters). Does anyone have any experience with this DMC40218 LCD module? Is there any specific procedure I should follow to initialize it correctly so it works with a 4-bit data bus? I would very much like to use it because of the number of characters it provides, and I actually need to use a small 12-key keyboard with this design. Any ideas? Thanks in advance.