Just recently bought a 128x64 character LCD, which uses the ST7920 controller as far I can tell from the website specs/ Q&A.
I am following one of multiple online tutorials using the SPI mode and the U8G2 Library, and I cannot get the display to show anything. I have tried a few of the test example sketches and the constructor line that should work is:
I have read that the PSB pin is sometimes tied HIGH on some of these LCD modules but I have measured it and it is not the case on mine, so SERIAL mode should be working with PSB tied low?
The pcb in your photo does not match the photo in your BangGood link.
However both pcbs are printed 12864B. Both have a PSB pin.
So I would be 99.5% confident that you have a ST7920.
Your wiring looks ok but I would be much happier if you put the
/* data=*/ 11
i.e. RW wire on row #15,col #J
Then we could identify which wire goes to which hole on the breadboard.
Note that Chinese male-male jumpers are crap. Always test them before every use.
Thanks for an excellent post. i.e. links to hardware and software + photos.
Thanks David, I have changed the wiring to bare-bones and used male-to-female jumpers in hopes of a better setup (see attached images).
I am suspicious my LCD is different to all the others on the internet/ received a bad sample, but I don't think I have done enough testing to say that just yet.
With the new wiring I have also tried this library for the ST7920 without success. I have adjusted the in-built potentiometer to see if it was a contrast issue to no avail. I have discovered that this particular model has a 27K pull-down on PSB on R9 which I verified by reading 0V on the PSB pin when the LCD was on. I can also confirm the RST pin works when grounded, clearing the LCD pixels.
Before I go ahead and ruin my chances of getting this product returned (de-solder R9) perhaps I need to figure out the parallel communication and attempt that?
First off. Ask BangGood for help. Attach your photos
BangGood will either provide new information e.g. new different controller, new example, new library
Or they just replace the display.
Please do not attack the pcb. It is unlikely that they ask you to return it. But if they do ask it should be unchanged.
Have you tried rotating the VR control? i.e. just below the J6, J5 solder-bridges.
Personally, I would try it in 4-bit parallel mode. i.e. connect it as if it was a regular 16x4 Character LCD with LiquidCrystal.h
You should see some text.
By potentiometer I meant the VR control which I have tried without success. I have reached out to BangGood and in the meantime I will attempt the 4/8-bit parallel mode with the LiquidCrystal library and the other libraries.