Trouble getting this LCD to work

Thread Starter


Joined Sep 7, 2011
I don't know what the deal is. I have probably bought 5 different character LCD screens thinking I have bought the wrong one.

I got this one:

and they don't have a datasheet for it. They just give you the datasheet for the 5volt version. Which is kind of lame. I got it hooked up to a power supply and the LED turns on. Someone told me I should unhook everything but the LED pins and be able to adjust the voltage on the contrast pin in order to get little black boxes in each character cell to ensure that the contrast is set. I tried this today and couldn't get anything. Blank the whole time.

I got sick of not having a descent datasheet so I got this from newHaven:

I hooked this thing up to a power supply and I couldn't even get the LED to light up at all. On the bright side, there isn't a contrast pin I have to deal with so that is a load off my shoulders.

I really need to figure out how to write to one of these things. I am going to drive it with an MSP430 microcontroller and I posted my c code to test the display on the MSP430 forum and it seems sound. I am just struggling with all the hardware I guess (which seems like it would be the easy part).


Joined Jan 28, 2005
The Newhaven display you have purchased uses the ST7066U controller. This controller is equivalent to the ubiquitous HD44780. Some information that I have encountered on the Internet indicates that the initialization instruction sequence for the two displays is the same. The one thing that they say is that the ST7066U controller may need longer delays between initialization instuctions than those called for by the HD44780 controller.

If you are using code intended for use with the HD44780 based LCD display, you may want to try increasing the delay times being used during the initialization.



Joined Apr 24, 2011
crobertsbmw: I've been using these things for years now. Last week I hooked up two more (both a 40x4 and an 8x1) on a development platform I'm making up and neither one worked. Took me a day to first straighten out some bad library code and find the mis-wire in the schematic. Moral of the story is they ain't easy to get to work, if you miss one thing then NOTHING happens.

Why don't you start with posting your schematic. A photo of the board may help too.

It's strange even the back light LED doesn't work, that should be the easy part.


Joined Oct 2, 2009
I have used these many times without any problems. You need to post your interface connections (schematics) and then post your code.


Joined Oct 29, 2009
Post your schematic and code. Without that we just need to guess.

Did you use the code in the data sheet?

Are you certain of all of your connections?

What have you done to troubleshoot? Did you verify your the inputs to the LCD were changing accordingly?

This really should have been posted in the embedded forum (assuming you are using an MCU).