Using the STM32H7 Color Lookup Table (CLUT) with SquareLine Studio


We’re trying to implement a user interface using the SquareLine Studio software on an STM32H7 processor. We’d like to use the LTDC’s “Color Lookup Table” functionality, as we’re limited on the amount of RAM that can be used for the framebuffer on this particular device, and we don’t anticipate the usage of more than 256 colors at a time.

Does anyone have any recommendations for the best way to accomplish this using SquareLine Studio? We are also using the LVGL driver.

Thank you,

LVGL dont support L8 i mean. But in flushcb you can convert 565 to L8 CLUT. Question is your RAM will use one full framebuffer L8 and some 565 lvgl buffer.

Actually there’s 8bit-color support in LVGL v8 but it’s not palette oriented, it uses 3 bits for red and green and 2 bits for blue. If you want design with your own STM32 LTDC CLUT palette in SquareLine Studio I guess your best option would be to use 32bit color during design and add those same colors (in the same order as in the CLUT) to the default theme’s global colors and use only those colors on the widgets so you’ll see the same colors that will eventually appear in the output. But it would take some (preferably automatic) modification on the exported code to replace the theme-colors by simple 8bit CLUT index-values. And you’ll need to set 8bit color-depth (L8) set in your exported LVGL code (lv_conf.h) and have to process these 8bit values as indexes by the custom STM32H7 CLUT flush/driver code that will send these to the display and use the CLUT to show the colors.