i2c/SPI LCD Backpack and LCD just blinks

[therenegademaster]

I ordered 2 20x4 LCD screens and i2c backpacks. I soldered everything together and uploaded the example from the modified library, and the screen just blinks The backlight doesn't seem to have any characters, or be affected by adjusting the contrast. I'm not even sure how to troubleshoot this. When it happened the first time, I thought I might have a solder bridge somewhere, but I don't think I could have made a mistake like that twice with two different screens.

Have you heard of this happening before?

[therenegademaster]

Here's a picture of what I have:

[adafruit_support_bill]

Did you try wiring up the LCD only - to make sure it works properly without the backpack?

[therenegademaster]

Well, it doesn't work anymore . I think all my soldering and un-soldering killed them both

[adafruit_support_bill]

You may have lifted a solder-pad or two, but it is unlikely that unsoldering would have caused any electrical damage to the display. Post a photo of where you think there might be damage and show us what it does when the backlight & contrast are hooked up as in the LCD tutorial.

[mattiep321]

Just Blinks! I was using my LCD fine, but wanted to reduce the number of pins, so I bought the backpack and soldered it up. I opened the HelloWorld_i2c sketch, loaded it into my Uno and i get blinky blinky but no text. ??? I tried the pot on the back and no luck...Is this common with this backpack? I will try unsoldering and using the LCD by itself...

[adafruit_support_bill]

Can you describe the blinking? Is it the backlight or the characters? Is it steady or intermittant? Have you tried the SPI interface?

[vmarguerie]

Hi,

I have the same problem with my LCD Backpack (just à Backlight and no characters).

The solution I've just found is to tie the VO (Pin 3 of the LCD) to the Ground.

It works good now...but why ?

I use Arduino Mega 2560

[housefly88]

I am having the exact same problems with a 16 * 2 red LCD.
I soildered in the 16 pin male header to the LCD and a female
Header to the backpack (I am not sure how I am going to mount it
yet so I have my self the option of disconnect) anyway when I upload the
Hello_Wolrd sketch, I get a blinking LCD screen with no text,
I going to try the solution posted above, and if that dosent work, I will
Try test the LCD with out the backpack.

[tastewar]

Have you tried adjusting the trimmer (contrast, I think?). I didn't see anything on mine until I did (I have the red one as well).

[magorian]

I have a similar problem. Just bought from Adafruit a blue 16x2 lcd, soldered on headers, backlight and contrast adjustment work fine per the tutorial (1 row of blocks @ max contrast). But have tried wiring up "Hello, world" and other tests multiple times from different Arduinos (and have it working from a 40x4 green lcd), and never see any characters no matter the contrast. I even resoldered the headers with my Hakko and tested for shorts, but I think it must be fried. Thanks. Dan

[adafruit_support_bill]

@Magorian - are you using the backpack, or wiring direct to the Arduino?

[housefly88]

@ tastewar:

yes I have adjusted the contrast on the backpack from one extreme to the other, with no results other than the backlight changing, still no text. I tried shorting out the 3rd pin on the LCD (VCO) to ground and ended up getting a row of charaters, well actually not characters but a row of solid blocks on line 2 of the LCD. I am going to try wiring up the LCD with out the backpack, and start my trouble shooting adventure from there. I will deffently post any soultions if I come across one, as it seems there are quite a few people having the same issue with the backpack. Thanks for your reply

//edit: I do not even get a row of blocks at full contrast, with the backpack, just a blinking screen

Best

Housefly

[housefly88]

Ok, upon wiring up without the backpack, using the 10k trim pot, Everything is functioning properly with the LCD.

I used the stock LiquidCrystal Library

//any suggestions on why the LCD is blinking when using the Backpack?


Thanks in advance

[magorian]

Wiring direct, sorry maybe shouldn't have posted in this backpack thread. Dan