Force partial refresh with SSD1681 eink, Zephyr and LVGL

[ParalaX002]

Hi,

Not sure if it's a zephyr issue or a LVGL issue, so I hope I'm at the right place.

I use an 1.54 eink display with the SSD1681 driver, and LVGL. Everything goes well except that partial refresh is only triggered when a very small portion of the screen is used. I know for a fact that partial refresh on this screen works even with changing a big part of the screen, because it works with an Arduino driver, but here there is something somewhere that prevent that to happen.

Since I can partial refresh when changing only a little thing (like 1 or 2 characters), I now my device is correctly configured.

Does someone have some experience with this?

Thanks in advance.

[ParalaX002]

Hi again,

So after discussion on discord and investigation, it turns out the "problem" comes from this code:
https://github.com/zephyrproject-rtos/zephyr/blob/main/modules/lvgl/lvgl_display_mono.c

In function lvgl_flush_cb_mono, lvcl override the blanking. So for me the solution is to disable that, and I do the blanking myself.
Also of note is that there is this configuration:

CONFIG_LV_Z_VDB_SIZE=100

It says the size of the buffer in percent. My screen being little, I can use a buffer the same size as the screen. Failing to do so will result in tearing.

[Øyvind]

Thanks for providing the solution! Are you able to use the eink display as intended?

Kind regards,

Øyvind

[ParalaX002]

Yes everything is good now :)

[Øyvind]

Awesome! Good luck on the journey!