ST7920 Graphical LCD not Working

[barefoot_engineer]

Hello!

I am having trouble with a 128x64 ST7920 graphical LCD. I followed the tutorial from Bas on Tech, but only the LCD backlight comes on.

I ordered this LCD on ebay (I don't know where, but if that link would be useful, I can find it for you in my search history.)

I can also attach an image if that would help.

Thank you for any help!

--Tutorial Link---

Tutorial 16 - 128x64 ST7920 graphical/dot-matrix SPI LCD

[anon57585045]

@barefoot_engineer

I can also attach an image if that would help.

By default you are asked to.

How to get the best out of this forum

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[barefoot_engineer]

An image is included here.

[anon57585045]

Schematic?

[barefoot_engineer]

The finished wiring is included in the tutorial (see Step 5).

[anon57585045]

Please read the link I gave you. There it is explained why you must post things like that here, not link to them.

Many tutorials do not provide real schematic diagrams. If this is one of those, please draw one.

[barefoot_engineer]

Thank you! I have a wiring diagram for you below.

Unfortunately, the tutorial diagram is a fritzing diagram (even though the link said not to use them) because that's all I have.

Also, KiCad isn't supported on my old 2010 MacBook Pro running macOS High Sierra, and my new (er) Linux PC needs repair. Sorry about that.

[anon57585045]

@barefoot_engineer

Unfortunately, the tutorial diagram is a fritzing diagram (even though the link said not to use them) because that's all I have.

I'm sorry but that is not useful. It is low resolution so you can't read the connection labels. Also this kind of diagram includes a proto board, which may or may not correspond exactly to the one you have. It even uses a different type of Arduino than yours.

So please take a pen/pencil and paper, and draw a proper schematic, take a photo and post it.

[barefoot_engineer]

If you need a better drawing I can make that tomorrow.

[anon57585045]

Thanks, that will get people thinking. The forum is international, runs 24/7.

I see a "To 3.3V". Why is the backlight running on that?

I see "Don't see how that would affect anything"... look at the Uno and Mega pinouts. They're different!

[barefoot_engineer]

Ok! Thank you! I will be back tomorrow afternoon.

Have a good day!

[barefoot_engineer]

Thank you!

However, from what I know, some graphical LCD backlights do indeed run on 3.3v. The tutorial I followed also says to use 3.3v, and the backlight seems to run at a nice brightness level when powered with that, so I would not like to try 5 volts as that could ruin it.

And then for the part about the Mega 2560, I have replaced it with an an Uno and uploaded the sketch to it, but still no luck.