Read this page:
http://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controllerSee the Instruction Set? A lot of chips that are HD44780 clones have the same commands ... so if you look into lcd displays and you read the datasheet and find those instructions, it will be HD44780 compatible.
For example, go to digikey.com at LCD Displays Alphanumeric and Character:
http://www.digikey.com/product-search/en/optoelectronics/display-modules-lcd-oled-character-and-numeric/524437Select Parallel interface because the HD44780 is working in either 4-bit or 8-bit mode, so using several lines in parallel from arduino. (note here: There are some lcd displays that are serial, using just a couple of wires... which actually still use a hd44780 close and there's just a simple chip in between doing the serial to parallel conversion)
Now select the number of characters you want, for example 80, to get a 4 x 20 digit display.
Now go through each and read the datasheet - you'll find probably 90% of them have those instructions in the datasheet. That means they're compatible.
For example :
http://www.digikey.com/product-detail/en/NHD-0420AZ-FL-YBW-33V3/NHD-0420AZ-FL-YBW-33V3-ND/2773600It's a 3.3v 4x20 display ... datasheet says at page 2:
Functions and Features
• 4 lines x 20 characters
• Built-in controllers (ST7066U)
• +3.3V Power Supply
• 1/16 duty, 1/5 bias
• RoHS compliant
and at page 5 you have a link to the full datasheet for that ST7066U which you'll find it has the same instructions as HD44780 ... at page 17 in that link.
and if you're still not sure, at page 6 you have the instructions, which are, again, the same as the ones for HD44780.
-=
Or let's take another example:
http://www.digikey.com/product-detail/en/C-51847NFJ-SLW-ADN/73-1249-ND/769330If you open the datasheet, you'll notice there's no command set in it, but if you look at page 10, you'll see in the diagram that all the pins go into a box that says "NT8331 or equivalent" - that's the chip on the lcd display.
So now you can search in google for "NT8331 datasheet" and you find the datasheet for it... I've put it here for your convenience :
http://savedonthe.net/download/407/NT3881D.htmlIf you look in this datasheet at page 16, it's the same Instruction set... so this chip is also a clone of that Hitachi HD44780 ... bingo...
Pretty much all lcd displays that look like the one above, with 8 pins for data signals, are using those HD44780 clone chips. Some have the pins on the side, in a 2 x 8 layout, like this one :
http://www.digikey.com/product-detail/en/NHD-0220FZ-FSW-GBW-P-33V3/NHD-0220FZ-FSW-GBW-P-33V3-ND/2773592 ... still the same clone chips..