Help w/ Display (Drivers SPLC780D OR ST7066U)

Using Arduino Displays
#1

I have just recently purchased some displays from New Haven Display and the drivers listed are SPLC780D OR ST7066U, from doing some reading prior to purchase, I saw that it is compatible to the Arduino because it's the same coding for the HD44780 driver (if I worded that incorrectly I apologize). I had a sketch running already that had a HD44780 screen on it and wanted to change the screen out to this new 4x20 display I purchased (NHD-0420AZ-FL-GBW-3V3). When I hooked it up, to no surprise it was NOT working properly. I tinkered around a little, did some reading (which has confused me more) and here I am!

To make this easier, I'm working off of the "Hello World" sketch which has the pin out as follows:

  • LCD RS pin to digital pin 12
  • LCD Enable pin to digital pin 11
  • LCD D4 pin to digital pin 5
  • LCD D5 pin to digital pin 4
  • LCD D6 pin to digital pin 3
  • LCD D7 pin to digital pin 2
  • LCD R/W pin to ground
  • 10K resistor:
  • ends to +5V and ground
  • wiper to LCD VO pin (pin 3)

The display is on, and working it just has symbols and blacked out segments...

Here is the datasheet from the LCD display:
http://www.newhavendisplay.com/specs/NHD-0420AZ-FL-GBW-3V3.pdf

Any help would be much appreciated! If I can supply any additional information please let me know what you need. Thank you in advanced for your help!

Pete

#2

According to the data sheet that you linked to this is a 3.3v device. Have you taken that into account?

Don

#3

floresta:
According to the data sheet that you linked to this is a 3.3v device. Have you taken that into account?

Don

Yes sir.

#4

You aren't providing much information. Are you sure that the current drain of the backlight isn't causing your supply voltage to sag?

Don

#5

Yes, Voltage is good. The display is working fine, it's just displaying random nonsense. What information could I provide you that would help with diagnosing the issue? I really do appreciate your help on this!

#6

floresta:
You aren't providing much information. Are you sure that the current drain of the backlight isn't causing your supply voltage to sag?

Don

I thought about this a little more, I have a regulator circuit on this to step down to 3v... Now, it's working perfect! Well other than I had to change the resistor on the contrast. When I have the LCD on the text disappears and when I have it off it works fine. I have to find the right resistance that will work for both. Not really a big deal. Thanks for the help Floresta!

#7