After searching the forum, I could not find a subject that included my problem. I have had displays working with all kinds of Arduinos for the past 2 years. Recently, I hauled out an uno and hooked up a new display to it. It's the standard parallel interface I've used many times before. After many checks of the wiring and changing out Arduinos and testing displays with other working projects, I still get a blue, blank display. I've tested all the voltages on the display. Uploaded "Hello World" many times. Nothing!
This is like I'm being punked. Please look at the wiring in the picture and tell me what stupid mistake I'm making. Sheesh this is embarrassing!
Start by checking the continuity of each of your wires.
A photo with a little more illumination would help - things are a little murky on the far side of your UNO. Also, some of the wires disappear off the top edge of the picture.
EDIT: What happens when you disconnect all except pins 1, 2, 3, 15, and 16? You should see the top row full of pixels and the second row blank.
I have tested all the wires and used different ones as well. I get no pixels with data lines removed. Remember, I tested the display with another circuit and it works perfectly. VO has +2.8v currently. I have tried adjusting the contrast bias with no result. I also included a better picture of the wiring. Sorry about that.
I highly doubt this has anything to do with it, but why are you running the backlight off the 3V3 instead of the 5V?
And how are you powering the Arduino (known, adequately powered USB port, or?)
Your JPEG shows the LCD pin#2 being supplied by 3.3V. And VO pin#3 coming from the blue pot.
The LCD requires 5V on pin#2 and about 0.4V on pin#3. As you vary the pot between 0V and 0.5V you will see some contrast. If your pot has 2.8V on VO it will never show anything on the LCD.
An excellent clear photo. An excellent strategy to use colour coded jumper wires to match your LCD pins.
Just supply pin#2 with 5V and adjust the pot to give about 0.4V.
It looks as if your Backlight Anode is connected to RESET and the Kathode to 5V.
So connect your backlight Anode to 5V too. The Arduino 3.3V regulator is too wimpy. The backlight Kathode to 0V.
Incidentally, life is much easier with an I2C backpack. 4 wires and you are done!
I Knew it was something really stupid... Thank you very much David for pointing out the wrong VO bias!! I never paid attention to the voltage on previous projects. I always set it for comfortable viewing.
The wiring was correct all the time as I went over it 20+ times.
Thanks again! You da man!!
Rudy
