I managed to get a Hantronic 2x16 working in 4 bit mode but a 2x20 Varitronix will not work and I also can’t get a Varitronix mdls20468 4x20 to work and their datasheet is worthless.
The pinout in the datasheet looks standard and the samsung part is a clone of the hd44780.
The LiquidCrystal library should work if they are hooked up correctly to the Arduino.
If you describe the exact symptoms of failure and post a picture of your wiring, I expect you will get the help you need.
did you plug the 3 parts into the exact same circuit? Do you have a potentiometer that you can use to adjust the contrast voltage?
The Hantronic works. The only difference in wiring is the backlight pins. I think it's a timing issue with these displays. They work fine in the device that I salvaged them from.
The LCD's are coming on as I can adjust contrast but they don't receive data.
I'm looking for someone that has made that brand work. If I can't get them to work I'll pick up ones that will.
I just found the Enhanced LCD library for larger displays, that may get the 4x20 working.
If its a timing issue be sure to try the last version of the enhanced LiquidCrystal series; that one has significantly lengthened some delays.
If I understand correctly, when you adjust contrast you see solid blocks on all rows?
f you describe the exact symptoms of failure and post a picture of your wiring, I expect you will get the help you need.
Posting the actual code (sketch) used with the picture is important too.
The wiring is identical to a Ladyada article and works with the 2x16 LCD using the standard LiquidCrystal library and the examples that come with 0018.
I'll give the other library a shot. I have access to a large supply of these things and if I can get it to work I may buy them cheap to give away.
It looks like you had the Hantronic display in the circuit and it worked. Then you put the Varitronix display in and it didn't work. Did you try putting the Hantronic display back and verify that it still works? You may have messed something up while exchanging displays.