Negative RGB 16X2 Character Display Problems

[elecfan]

I recently bought one of the negative RGB displays (http://www.adafruit.com/products/399) and I haven't been able to get it working with my Arduino project. After searching around for a while, I found a post (viewtopic.php?f=47&t=25162) and used the same setup.

I have simple code to turn on the backlight for the Arduino (using PWM), but the backlight doesn't light up. When I unplug the 5V (Pin 2), then the backlight will turn on. When I plug pin 2 back in, it turns off again.

Any suggestions?

[elecfan]

I now have the LCD displaying characters, but it isn't even remotely close to what it should be. When I upload the Hello World example in the LiquidCrystal library, I get the following:
http://www.youtube.com/watch?v=oPRli3fVrjE

As you can see, I still have the issue of the 5V VCC dimming (effectively removing) the text that is printed. And instead of hello world and then a counter, it's just random giberish and question marks. I've checked the data lines because I thought having those out of order would make a difference, and they're in the correct order for the example.

[adafruit_support_bill]

Post some photos that clearly show all your connections.

[elecfan]

Here's what I have. There's quite a few connections so it isn't perfectly clean.

DSCN1206.JPG (961.8 KiB) Viewed 695 times

The mapping is:

LCD | Arduino
GND (1) | GND
VCC (2) | 5V
VO (3) | Output of Potentiometer
RS (4) | D13
RW (5) | GND
EN (6) | D12
DB4 (11) | D11
DB5 (12) | D10
DB6 (13) | D9
DB7 (14) | D8
BLK (15) | 5V
R (16) | PWM3
G (17) | PWM5
B (18) | PWN6

and running this code:

Code: Select all

#include <LiquidCrystal.h>

LiquidCrystal lcd(13, 12, 11, 10, 9, 8);

void setup() {
   lcd.begin(16, 2);
   lcd.print("hello, world!");
}

void loop() {
   analogWrite(3, 0);
   analogWrite(5, 255);
   analogWrite(6, 255);
   lcd.setCursor(0,1);
   lcd.print(millis()/1000);
}


The whole setup (wiring + code) results in a red backlit LCD with "11" separated by spaces taking up the whole row in both rows. If I tilt the breadboard a bit or otherwise touch the LCD, random characters appear.

[adafruit_support_bill]

It looks like your data lines are connected in reverse order (pin 4 if the LCD should go to pin 9 of the Arduino).

From the perspective of the photo it is hard to see what pins you have the RBG lines connected to. It should be pins 3, 5 & 6.

[elecfan]

According to the example included with Arduino, when you initialize a LiquidCrystal object the format is:
LiquidCrystal lcd(RS, EN, D4, D5, D6, D7)

So the pins should be in the right order the way I have them. 3, 5, and 6 are connected in the right order as well (see the listed mapping in the previous post).

Also, from the picture, you can see the backlight (red) is on. If I take out the VCC line on the LCD (Pin 2), then the text gets a lot brighter. Disconnecting the power line shouldn't make it get brighter, but it does.

[adafruit_support_bill]

the pins should be in the right order the way I have them

It is much easier for us to verify things if you hook them up as in the tutorial.

If I take out the VCC line on the LCD (Pin 2), then the text gets a lot brighter

Sounds like there is a short somewhere. It looks like there is some soldering on the other side of the display. What's the story there?

[elecfan]

I originally soldered the header onto the wrong side. The project that I'm working on needs to have the correct orientation when placed in the enclosure. I've since removed some of the solder from those connections and cleaned them up.

[adafruit_support_bill]

OK, Contact support@adafruit.com for a replacement display & reference this thread in your message.