LTDC Line event callback vs ltdc preload buffer.

[MM..1]

HI

i try in callback repeat one memory line in two display lines, but display still show no doubled image.

Config is L8 CLUT framebuffer .

Code

        	LTDC_Layer2->CFBAR -= 320;
        	LTDC->SRCR = (uint32_t)LTDC_SRCR_IMR;
        	HAL_LTDC_ProgramLineEvent(hltdc, LTDC->LIPCR+2);

callback work every second line on visible area, but dont double. I mean because is preloaded in buffer. Exist way to go?