Uno + U8GLIB + Nokia 3410 Display (PCF8812) = artefacts

Other Hardware Displays
1

Hi,

I am actually experimenting TNT display with salvages parts from nokia phones. I discovered the very promising U8G library, and a very interesting blog post (Nicu FLORICA (niq_ro): Afisaj de Nokia 3410 comandat de Arduino).

The first example of this page with the correct screen size just works as expected : Arduino Playground - PCD8544
I believe the display is OK since it works with this example.

I then tried U8G with the Hello World example and also the GraphicsTest one, using "U8GLIB_PCF8812 u8g(13, 11, 10, 9, 8);"
With this setup I end up having artifacts on the screen (see attachment). What I see :

  • every 16th line starts with a dot on the left.
  • every 8th line have its own pixels on, but has also the ones from the 7th line above and 1 pixel to the right (although this is visible only one line in the attached photo).

The blog above does not mention the same problem so I tried an older version of U8Glib (v1.14 from 1 year ago) but with the same result.

Maybe the controller I have is different from PCF8812 ? Tried PCD8544 but same artifacts. Also tried HW SPI constructor ( U8GLIB_PCF8812(cs, a0 [, reset]) ), but blank screen.

I have tweaked the connexions without result. Maybe my cables are still a bit long and not soldered, however I find strange that the artifacts are not random : they are always the same every loop of the GraphicsTest.

I would gladly take some advice from more experienced users about this !

IMG_2806.JPG
IMG_2806.JPG800×600 90.9 KB

2

Replying to my own thread.
Th problem seems to be in voltage level conversion. I only used 10k resistors like I found on some threads on the net, but it does not seem to be good enough.

I was lucky to connect a flat battery pack delivering less than 5v to the arduino, which resulted to around 3.5v to the atmega, and the artifacts just vanished !

I'll have to test it on a 3.3v pro mini later. And I'm actually checking about 'real' logic level converters. I find these https://learn.sparkfun.com/tutorials/using-the-logic-level-converter interesting, but I read that fast spi communication (maybe like U8G does) may have to be slowered down to work with these.

Thanks anyway to those who took the time to read my post !

Sassa