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LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero
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LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Thu Jun 01, 2017 12:51 am

Hello,
I'm trying to get my RGB Backlight 16x2 LCD working with my Raspberry Pi ZeroW, via the LCD Backpack.
Links to LCD and Backpack:
https://www.adafruit.com/product/399
https://www.adafruit.com/product/292

I've connected everything, probably did something wrong... loaded the i2c software, and Adafruit LCD library...
I connected 4 wires from the LCD Backpack to the Pi like this:
GRD --> Gpio 6
5V ----> Gpio 2
CLK---> Gpio 5
DAT---> Gpio 3

When I run this: sudo i2cdetect -y 1 I do show an i2c connection at 20:20

Wasn't exactly sure what example python script to run from the Adafruit_Python_CharLCD/examples directory, but I think it was char_lcd_plate.py
I ran: sudo python char_lcd_plate.py
No errors were reported, but no LCD lighting up either.

I've tried turning the contrast up/dwn on the back of the Backpack, could see 1 row of LCD's light up dimly, but no text...

Any ideas what I'm doing wrong? I'm attaching photos of all the connections.

thanks!
-Sean

IMG_1800.JPG
back of the backpack>
IMG_1800.JPG (774.78 KiB) Viewed 361 times

IMG_1804.JPG
Raspberry Pi Zero W
IMG_1804.JPG (573.55 KiB) Viewed 361 times

IMG_1805.JPG
RGB LCD
IMG_1805.JPG (430.48 KiB) Viewed 361 times
Last edited by seanman3000 on Thu Jun 01, 2017 1:05 am, edited 1 time in total.

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by adafruit_support_carter on Thu Jun 01, 2017 12:22 pm

Check out this guide:
https://learn.adafruit.com/character-lc ... bone-black

It might be as simple as the python script you ran. The char_lcd_plate.py script is intended for a different product and actually waits for some button presses before displaying anything. Try running char_lcd.py.

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Thu Jun 01, 2017 3:20 pm

I've read through that guide a few times...I never saw mention of the Backpack hooked up to a Pi in any of those.
I've also tried running all the python scripts in the ./examples directory, no luck with any of them.

The backpack has only 16 connections, while the RGB LCD has 18.... Could that be an issue?

Do the connections I have in the photos/description look correct?

thanks!
-Sean

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by adafruit_support_carter on Thu Jun 01, 2017 7:16 pm

The backpack (in I2C mode) is essentially this:
https://learn.adafruit.com/character-lc ... spberry-pi

The backpack has only 16 connections, while the RGB LCD has 18.... Could that be an issue?

My understanding is that it only matter for the backlight. Being RGB, there are two extra pins vs. a single color backlight module. There is verbiage on the product page about this.

Do the connections I have in the photos/description look correct?

Yes. And the fact that the i2c-detect shows 0x20 means it sees the MCP. Maybe the problem is between there and the display. Your soldering looks OK from what I can see in the photos, but can you post some more photos with closer shots of this.

Or, do you have an Arduino or similar that you could use as another way to drive the display?

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Thu Jun 01, 2017 10:11 pm

I have a couple other Pi's if you think it'd be worth trying that out....no Arduino's though.

Here's another photo of the soldering...

IMG_1808.JPG
IMG_1808.JPG (660.14 KiB) Viewed 317 times

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Fri Jun 02, 2017 12:34 am

I re-soldered the other connections, just in case... but results are the same.

IMG_1810.JPG
IMG_1810.JPG (736.11 KiB) Viewed 309 times


All I can get is a very faint upper row of LCD characters turned on..... but this happens when power is plugged into the Pi.... I haven't even run any code yet, and this is what the display looks like:
IMG_1813.JPG
IMG_1813.JPG (652.58 KiB) Viewed 309 times

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by adafruit_support_carter on Fri Jun 02, 2017 10:40 am

I have a couple other Pi's if you think it'd be worth trying that out....no Arduino's though.

OK. Just wanted to test it with a 5V board to see if that worked.

Looking through the examples in a little more detail, it looks like the one to try is:
https://github.com/adafruit/Adafruit_Py ... lcd_mcp.py

You said you tried them all, so assume that means that one as well. When running that one, what was the behaviour?

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Fri Jun 02, 2017 1:55 pm

Tried that one again, no luck. Running the script gives no errors, and nothing on the LCD changes... It just has that dimly lit top row squares turned on the entire time.

Could it be that this backpack is incompatible with the RGB LCD?

-Sean

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by adafruit_support_carter on Fri Jun 02, 2017 5:26 pm

Could it be that this backpack is incompatible with the RGB LCD?

It's been done before:
viewtopic.php?f=47&t=114427

Can you try temporarily grounding the two extra pins as was done in that post?

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Fri Jun 02, 2017 6:01 pm

No luck... Display stays partially illuminated as before... I haven't seen any backlights come on at all...

-Sean

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by adafruit2 on Sat Jun 03, 2017 10:54 am

this code example
https://github.com/adafruit/Adafruit_Py ... lcd_mcp.py
is for the Pi shield not backpack, which has a different pinout. i dont know that we have a guide/tutorial for this particular item and Pi!

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Sat Jun 03, 2017 4:27 pm

Thats what I was wondering... Do you think the RGB LCD would be compatible with the Backpack? Do you know where in the code I'd change things to get it to work?

thanks!
-Sean

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by adafruit2 on Sat Jun 03, 2017 5:13 pm

it can, but you'd have to do quite a bit of re-working to make the library compatible. we don't have any code - but if you google around you may find something? let us know if you do!

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by seanman3000 on Sat Jun 03, 2017 6:45 pm

Do you think it would be easier to just wire this up, without the Backpack at this point? Like in this example? https://learn.adafruit.com/character-lc ... ack/wiring

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Re: LCD Backpack, RGB LCD 16x2, Raspberry Pi Zero

by adafruit2 on Sat Jun 03, 2017 8:19 pm

yep - we know that works!

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