Object rendering issue


What MCU/Processor/Board and compiler are you using?

ST STM32F412 MCU with GCC Arm Compiler connecting to East Rising OLED display (PN: ER-OLED015-1C) over 4 wire SPI.

What do you experience?

Faint lines running outside the object container (eg labels, rollers etc). I can confirm that changing the object height or width of a label container for example doesn’t effect the faint lines. The lines seem to be tied to the top and bottom of text and run horizontally only.

What do you expect?

That the added objects shouldn’t effect the background display outside the defined bounds. Removing the object restores the background to the correct state.

Screenshot and/or video

Please see attached photos of the issue


Perhaps your display driver is flushing one extra line/missing one line?

Have you tried rendering the object in the same color as the background (making it essentially invisible) to rule out that it isn’t an artifact of the display itself?

I’ve seen similar issues when the pixel clock had an incorrect value. Do you see any changes if increase or decrease it (even significantly)?

Thanks guys,

I am pretty sure the issue is in the display driver as it shows when I load the manufacturers reference image and completely remove littlevGL. Its’s interesting that the issue disappears when I rotate 90 degrees but then I also get other issues with faint lines in the vertical plane instead of horizontal.

I’ve tried adjusting pixel clock, charge hold times etc. Pretty much tried changing every config register on the display controller to see if I could change it with no luck. I am currently talking with the manufacturer to see if they can assist me.

I’ll post the cause of the issue when I resolve.


With OLEDs, this is normal, and is the consequence of the relatively high row drivers/conductors resistance; or even inadequate primary LED (high voltage) source (which on some modules is integrated on board/foil/glass thus out of reach of the user).

Decrease overall brightness (I know you don’t want this, but it’s good also for the lifetime of OLEDs). Avoid high contrast changes between lines. Note that the consumption is given by the sum of all 3 colors, so white images on black are bad, red on green are OK.

Thanks wek,

Yes you are dead right!!, the manufacturer has confirmed the issue as Crosstalk. Basically regions become darker because when more pixels are turned on in the same scan line.

Hence will need to tweak the colour scheme with this in mind and look at reducing the brightness as you say.

Appreciate all your help guys,