My 12C/SPI LCD backpack for 3V-5V is Not Working!

This is Neal.
I am using a I2C/SPI CHARACTER LCD BACKPACK but it is Different then the usual Ones.
The usual one I buy looks like this:


But the ones I get from now look like this:

I connected the 12c connections the same as my last one and I connected the SPI connections the same as my last one but they don’t work.

What am I supposed to do Differently with this New LCD backpack?

If you could answer me that would be great.

Welcome to the DigiKey TechForum steneal1960.
I’m not seeing any real difference. Have you checked the datasheet?
If the SPI and address jumpers are installed the same, it should operate the same. I see the black board has a 3-5V jumper. Output to the LCD will be 5V, but if you break the jumper, the output will be 3V to the LCD.
Maybe one of the Engineers, that monitor the TechForum, can provide some knowledge about these boards.

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I Don’t know either.

And the New Adafruit Website about this New 12c/SPI backpack does not say much how to connect it.

They say that you only need to connect 2 connections for 12c without saying what those 2 connections are here:

And they say that you need to use 4 pins for 12c on the Backpack Without saying the Connections to the Arduino here:

Can you or someone else tell me the Connections and what is the whole thing about only using 2 connections?

If so that would be great.

Here is the website I got that from:


I soldered another New i2c / SPI character LCD backpack - STEMMA QT / Qwiic and it worked when I plugged it in to my Computer.

But when I turned on my 5V Battery Pack it still worked but when I turned the Battery Pack back on it Did Not Work just like my Other LCD with a i2c / SPI character LCD backpack - STEMMA QT / Qwiic that Does Not Work now.

So my 5V Battery Pack must have Fried my LCD when I Turned it On for Some Reason.

Why do you think it did that?

Should I use 3V instead?

Do I need to solder the 3V or 5v pad on the LCD Backpack Before I turn on a Battery Pack Connected to It?

If you could tell me what I should do about this that would be great!

Hi steneal1960,

A few questions got arosen. Kindly elaborate.

  1. Are you communicating to the backpack using SPI or I2C (that is defined in the source code)?
  2. What LCD display module are you using (maker, model)?

Note, some LCD modules support natively SPI, thus in a such case you won’t need the Backpack, as long as the interface specs match (logic voltages etc.).

Cheers, heke

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I am communicating with 12C logic.

I am using a Standardized 20 by 4 LCD from Adafruit here:

I agree that it might be a good idea to not use the LCD backpack.

I didn’t know you can make it work without the LCD backpack.

I also was thinking of just using a new type of LCD such as a 12C LCD Display like this one:

It is usually used for breadboards but I can just solder it instead.

The LCD Module

That LCD module is a 4 bit parallel data model requiring 6 pins for communication. So you will need the backpack if you want to use 2 pin serial I2C for communication.

Here’s the module schematic

Hi steneal1960,

In order to minimize the complexity, I usually go with e.g. Newhaven’s OLEDs, which support SPi and I2C, and are happy with 3.3V supply.

However, as you have already all the parts at hand, I guess, one just need to figure out why you’ll get the trouble described. Is there any chance to have a wiring diagram of your setup?

Cheers, heke

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Here is how it is connected:

5V on LCD Backpack going to 5V on Arduino Nano

GND on LCD Backpack going to GND on Arduino Nano

CLK on the LCD Backpack going to A5 on Arduino Nano

DAT on the LCD Backpack going to A4 on Arduino Nano

Although I think it would be easier to just use another type of LCD like the one you recommended for me or the other one I recommended.

I did find the pins they are referring to for I2C and SPI listed here , Pinouts | I2C/SPI LCD Backpack | Adafruit Learning System

Hi steneal1960,

Thank you for the wiring info. Looks fine. As you got the display working for a while with a different MCU board, I’d think that the display and backpack are fine. I wonder, could you explain the 5V batterypack thing. What is it and how do you connect it?

Cheers, heke