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PID 399: RGB backlight negative LCD 16x2 half squares
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PID 399: RGB backlight negative LCD 16x2 half squares

by benzvan on Mon Oct 05, 2020 1:17 pm

I have a RGB backlight negative LCD 16x2 that I'm having trouble with. Don't know if I failed or if it did.

Connecting it only to power and contrast, the default screen doesn't look right to me. Between the two images I've linked to here, I made no changes to the wiring. I've cleaned up the soldier a little since these photos but the result is the same. I have not yet tried the top set of connections. I have also tried the default Hello World arduino sketch with only the pins changed and the LCD showed only "Hello, W".

https://photos.app.goo.gl/Hau59RVXmPyeuw7M9

Purchased Sep. 11, 2020
Order no: 2362349-3765428329

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by benzvan on Wed Oct 07, 2020 5:17 pm

I just soldiered up the other side and tested it. Same symptoms.

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by adafruit_support_carter on Wed Oct 14, 2020 2:36 pm

Can you post another photo of your latest setup.

Where do these wires go?
wiring.jpg
wiring.jpg (109.45 KiB) Viewed 47 times

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by benzvan on Wed Oct 14, 2020 2:44 pm

I pulled stuff off the board for some other work but I'll put it back on and get you a new picture. If you look at the second photo in the gallery, that's basically the setup except I only had pins 1-3, 15, and 16 connected. The top wire to the top bus connects to ground and the bottom bus connects to +5v DC.

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by adafruit_support_carter on Wed Oct 14, 2020 2:48 pm

OK, it may be a wiring issue. Looks like the Feather's GND is not tied in. But let's see what the latest setup looks like.

Guide wiring for ref:
https://learn.adafruit.com/character-lc ... racter-lcd

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by benzvan on Wed Oct 14, 2020 3:26 pm

Actually, I did discover the GND wasn't tied in before I got to the "Hello, W" stage, but my later tests don't even have the feather on the board, just the weird pattern of blocks. Would you like me to set it back up with or without the feather? Or both?

I'll note the tutorial for this board doesn't actually mention connecting the feather's GND to the same GND as the LCD which, in retrospect, seems obvious and hard to avoid, but I was powering the feather with USB and the LCD with a DC adapter at the time.

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by benzvan on Wed Oct 14, 2020 4:56 pm

OK...I went back to the tutorial and I understand the ground problem I had was because I wasn't using USB and GND on the feather for my +5 and GND busses, so I am starting over following those instructions exactly.

I've added new images to the shared library linked in my original post and have set the backlight color to RED to distinguish from other images. So far, I have uploaded 2 images: 1) just the backlight wired, and 2) adding the logic/contrast. Basically the first two steps in the tutorial. The feather is running the sample "Hello, World" LCD sketch with zero modifications.

Right now, I'm seeing that I am not able to get the first row of squares on the LCD no matter where the contrast wiper is. I don't know if that is because there is something in the LCD buffer or because whatever problem it had is getting worse. According to the instructions, I shouldn't proceed beyond this point because it is not working as expected.

Note: This product has been refunded for my by Adafruit, so I'm happy to continue debugging this one but if you have other things you need to move on to, I'm ok tossing it and moving on. I'm replacing it with an SPI OLED since the LCD turned out to be a little large for my application. It would be nice if I could validate that it works or not in case I want to use it in the future.

Another note: Ether my LiquidCrystal -> Hello World sample sketch has been modified somehow, or the pins mentioned in the LCD tutorial don't match it. I'm also seeing that the tutorial says to use pins that do not exist on either of the feathers I am working with.

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by adafruit_support_carter on Wed Oct 14, 2020 7:06 pm

The guide doesn't show wiring for a Feather explicitly. So you would need to use available digital pins on your Feather and then change them in the code.

The wiring in the CircuitPython section may be more useful:
https://learn.adafruit.com/character-lc ... cuitpython
since it shows use with a 3V board, like the Feather.

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by benzvan on Thu Oct 15, 2020 11:30 am

Yep, that makes sense. Still stuck at step two though. The LCD is not showing any squares when powered on via 5v from USB and GND off the feather.

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Re: PID 399: RGB backlight negative LCD 16x2 half squares

by adafruit_support_carter on Thu Oct 15, 2020 5:19 pm

That may just be it's default behavior without any controller attached.

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Please be positive and constructive with your questions and comments.