LVGL8.3.7 flicking when fresh the screen

joey · February 23, 2024, 8:32am

Hi,
Recently, I port the LVGL8.3.7 on IMX6ULL with TFT(1280*800)
And when the screen has something to flush, it has flicking.
Here is the lv_conf.h
*

@file lv_conf.h
Configuration file for v8.3.7
*/
Copy this file as lv_conf.h
1. simply next to the lvgl folder
1. or any other places and
- define LV_CONF_INCLUDE_SIMPLE
- add the path as include path
  */

/* clang-format off */
#if 1 /Set it to “1” to enable content/

#ifndef LV_CONF_H
#define LV_CONF_H

#include <stdint.h>

/*====================
COLOR SETTINGS
====================/
#define LV_HOR_RES_MAX (1280)
#define LV_VER_RES_MAX (800)
/Color depth: 1 (1 byte per pixel), 8 (RGB332), 16 (RGB565), 32 (ARGB8888)/
#define LV_COLOR_DEPTH 32

/Swap the 2 bytes of RGB565 color. Useful if the display has an 8-bit interface (e.g. SPI)/
#define LV_COLOR_16_SWAP 0

/*Enable features to draw on transparent background.
It’s required if opa, and transform_ style properties are used.
Can be also used if the UI is above another layer, e.g. an OSD menu or video player./
#define LV_COLOR_SCREEN_TRANSP 1

/* Adjust color mix functions rounding. GPUs might calculate color mix (blending) differently.

0: round down, 64: round up from x.75, 128: round up from half, 192: round up from x.25, 254: round up */
#define LV_COLOR_MIX_ROUND_OFS 0

/Images pixels with this color will not be drawn if they are chroma keyed)/
#define LV_COLOR_CHROMA_KEY lv_color_hex(0x00ff00) /pure green/

/*=========================
MEMORY SETTINGS
=========================/

/1: use custom malloc/free, 0: use the built-in lv_mem_alloc() and lv_mem_free()/
#define LV_MEM_CUSTOM 0
#if LV_MEM_CUSTOM == 0
/Size of the memory available for lv_mem_alloc() in bytes (>= 2kB)/
#define LV_MEM_SIZE (64 * 1024U * 1024U) /[bytes]/

/*Set an address for the memory pool instead of allocating it as a normal array. Can be in external SRAM too.*/
#define LV_MEM_ADR 0     /*0: unused*/
/*Instead of an address give a memory allocator that will be called to get a memory pool for LVGL. E.g. my_malloc*/
#if LV_MEM_ADR == 0
    #undef LV_MEM_POOL_INCLUDE
    #undef LV_MEM_POOL_ALLOC
#endif

#else /LV_MEM_CUSTOM/
#define LV_MEM_CUSTOM_INCLUDE <stdlib.h> /Header for the dynamic memory function/
#define LV_MEM_CUSTOM_ALLOC malloc
#define LV_MEM_CUSTOM_FREE free
#define LV_MEM_CUSTOM_REALLOC realloc
#endif /LV_MEM_CUSTOM/

/*Number of the intermediate memory buffer used during rendering and other internal processing mechanisms.
*You will see an error log message if there wasn’t enough buffers. */
#define LV_MEM_BUF_MAX_NUM 16

/Use the standard memcpy and memset instead of LVGL’s own functions. (Might or might not be faster)./
#define LV_MEMCPY_MEMSET_STD 0

/*====================
HAL SETTINGS
====================/

/Default display refresh period. LVG will redraw changed areas with this period time/
#define LV_DISP_DEF_REFR_PERIOD 30 /[ms]/

/Input device read period in milliseconds/
#define LV_INDEV_DEF_READ_PERIOD 30 /[ms]/

/*Use a custom tick source that tells the elapsed time in milliseconds.
It removes the need to manually update the tick with lv_tick_inc())/
#define LV_TICK_CUSTOM 1
#if LV_TICK_CUSTOM
// #define LV_TICK_CUSTOM 1
// #if LV_TICK_CUSTOM
#define LV_TICK_CUSTOM_INCLUDE <stdint.h> /Header for the system time function/
extern uint32_t custom_tick_get(void);
#define LV_TICK_CUSTOM_SYS_TIME_EXPR (custom_tick_get())
#endif /LV_TICK_CUSTOM/

/Default Dot Per Inch. Used to initialize default sizes such as widgets sized, style paddings.
(Not so important, you can adjust it to modify default sizes and spaces)/
#define LV_DPI_DEF 130 /[px/inch]*/

/*=======================

FEATURE CONFIGURATION
=======================/

/*-------------

Drawing
-----------/

/*Enable complex draw engine.
Required to draw shadow, gradient, rounded corners, circles, arc, skew lines, image transformations or any masks/
#define LV_DRAW_COMPLEX 1
#if LV_DRAW_COMPLEX != 0

/*Allow buffering some shadow calculation.
*LV_SHADOW_CACHE_SIZE is the max. shadow size to buffer, where shadow size is `shadow_width + radius`
*Caching has LV_SHADOW_CACHE_SIZE^2 RAM cost*/
#define LV_SHADOW_CACHE_SIZE 0

/* Set number of maximally cached circle data.
* The circumference of 1/4 circle are saved for anti-aliasing
* radius * 4 bytes are used per circle (the most often used radiuses are saved)
* 0: to disable caching */
#define LV_CIRCLE_CACHE_SIZE 4

#endif /LV_DRAW_COMPLEX/

“Simple layers” are used when a widget has style_opa < 255 to buffer the widget into a layer
and blend it as an image with the given opacity.
Note that bg_opa, text_opa etc don’t require buffering into layer)
The widget can be buffered in smaller chunks to avoid using large buffers.
- LV_LAYER_SIMPLE_BUF_SIZE: [bytes] the optimal target buffer size. LVGL will try to allocate it
- LV_LAYER_SIMPLE_FALLBACK_BUF_SIZE: [bytes] used if LV_LAYER_SIMPLE_BUF_SIZE couldn’t be allocated.
Both buffer sizes are in bytes.
“Transformed layers” (where transform_angle/zoom properties are used) use larger buffers
and can’t be drawn in chunks. So these settings affects only widgets with opacity.
*/
#define LV_LAYER_SIMPLE_BUF_SIZE (24 * 1024)
#define LV_LAYER_SIMPLE_FALLBACK_BUF_SIZE (3 * 1024)

/*Default image cache size. Image caching keeps the images opened.
*If only the built-in image formats are used there is no real advantage of caching. (I.e. if no new image decoder is added)
*With complex image decoders (e.g. PNG or JPG) caching can save the continuous open/decode of images.
*However the opened images might consume additional RAM.
0: to disable caching/
#define LV_IMG_CACHE_DEF_SIZE 0

/*Number of stops allowed per gradient. Increase this to allow more stops.
This adds (sizeof(lv_color_t) + 1) bytes per additional stop/
#define LV_GRADIENT_MAX_STOPS 2

/*Default gradient buffer size.
*When LVGL calculates the gradient “maps” it can save them into a cache to avoid calculating them again.
*LV_GRAD_CACHE_DEF_SIZE sets the size of this cache in bytes.
*If the cache is too small the map will be allocated only while it’s required for the drawing.
0 mean no caching./
#define LV_GRAD_CACHE_DEF_SIZE 0

/*Allow dithering the gradients (to achieve visual smooth color gradients on limited color depth display)
*LV_DITHER_GRADIENT implies allocating one or two more lines of the object’s rendering surface
*The increase in memory consumption is (32 bits * object width) plus 24 bits * object width if using error diffusion */
#define LV_DITHER_GRADIENT 0
#if LV_DITHER_GRADIENT
/*Add support for error diffusion dithering.
*Error diffusion dithering gets a much better visual result, but implies more CPU consumption and memory when drawing.
The increase in memory consumption is (24 bits * object’s width)/
#define LV_DITHER_ERROR_DIFFUSION 0
#endif

/Maximum buffer size to allocate for rotation.
Only used if software rotation is enabled in the display driver./
#define LV_DISP_ROT_MAX_BUF (101024)

/*-------------

GPU
-----------/

/*Use Arm’s 2D acceleration library Arm-2D */
#define LV_USE_GPU_ARM2D 0

/Use STM32’s DMA2D (aka Chrom Art) GPU/
#define LV_USE_GPU_STM32_DMA2D 0
#if LV_USE_GPU_STM32_DMA2D
/Must be defined to include path of CMSIS header of target processor
e.g. “stm32f7xx.h” or “stm32f4xx.h”/
#define LV_GPU_DMA2D_CMSIS_INCLUDE
#endif

/Use SWM341’s DMA2D GPU/
#define LV_USE_GPU_SWM341_DMA2D 0
#if LV_USE_GPU_SWM341_DMA2D
#define LV_GPU_SWM341_DMA2D_INCLUDE “SWM341.h”
#endif

/Use NXP’s PXP GPU iMX RTxxx platforms/
#define LV_USE_GPU_NXP_PXP 0
#if LV_USE_GPU_NXP_PXP
/*1: Add default bare metal and FreeRTOS interrupt handling routines for PXP (lv_gpu_nxp_pxp_osa.c)
* and call lv_gpu_nxp_pxp_init() automatically during lv_init(). Note that symbol SDK_OS_FREE_RTOS
* has to be defined in order to use FreeRTOS OSA, otherwise bare-metal implementation is selected.
*0: lv_gpu_nxp_pxp_init() has to be called manually before lv_init()
*/
#define LV_USE_GPU_NXP_PXP_AUTO_INIT 0
#endif

/Use NXP’s VG-Lite GPU iMX RTxxx platforms/
#define LV_USE_GPU_NXP_VG_LITE 0

/Use SDL renderer API/
#define LV_USE_GPU_SDL 0
#if LV_USE_GPU_SDL
#define LV_GPU_SDL_INCLUDE_PATH <SDL2/SDL.h>
/Texture cache size, 8MB by default/
#define LV_GPU_SDL_LRU_SIZE (1024 * 1024 * 8)
/Custom blend mode for mask drawing, disable if you need to link with older SDL2 lib/
#define LV_GPU_SDL_CUSTOM_BLEND_MODE (SDL_VERSION_ATLEAST(2, 0, 6))
#endif

/*-------------

Logging
-----------/

/Enable the log module/
#define LV_USE_LOG 0
#if LV_USE_LOG

/*How important log should be added:
*LV_LOG_LEVEL_TRACE       A lot of logs to give detailed information
*LV_LOG_LEVEL_INFO        Log important events
*LV_LOG_LEVEL_WARN        Log if something unwanted happened but didn't cause a problem
*LV_LOG_LEVEL_ERROR       Only critical issue, when the system may fail
*LV_LOG_LEVEL_USER        Only logs added by the user
*LV_LOG_LEVEL_NONE        Do not log anything*/
#define LV_LOG_LEVEL LV_LOG_LEVEL_WARN

/*1: Print the log with 'printf';
*0: User need to register a callback with `lv_log_register_print_cb()`*/
#define LV_LOG_PRINTF 0

/*Enable/disable LV_LOG_TRACE in modules that produces a huge number of logs*/
#define LV_LOG_TRACE_MEM        1
#define LV_LOG_TRACE_TIMER      1
#define LV_LOG_TRACE_INDEV      1
#define LV_LOG_TRACE_DISP_REFR  1
#define LV_LOG_TRACE_EVENT      1
#define LV_LOG_TRACE_OBJ_CREATE 1
#define LV_LOG_TRACE_LAYOUT     1
#define LV_LOG_TRACE_ANIM       1

#endif /LV_USE_LOG/

/*-------------

Asserts
-----------/

/*Enable asserts if an operation is failed or an invalid data is found.
If LV_USE_LOG is enabled an error message will be printed on failure/
#define LV_USE_ASSERT_NULL 1 /Check if the parameter is NULL. (Very fast, recommended)/
#define LV_USE_ASSERT_MALLOC 1 /Checks is the memory is successfully allocated or no. (Very fast, recommended)/
#define LV_USE_ASSERT_STYLE 0 /Check if the styles are properly initialized. (Very fast, recommended)/
#define LV_USE_ASSERT_MEM_INTEGRITY 0 /Check the integrity of lv_mem after critical operations. (Slow)/
#define LV_USE_ASSERT_OBJ 0 /Check the object’s type and existence (e.g. not deleted). (Slow)/

/Add a custom handler when assert happens e.g. to restart the MCU/
#define LV_ASSERT_HANDLER_INCLUDE <stdint.h>
#define LV_ASSERT_HANDLER while(1); /Halt by default/

/*-------------

Others
-----------/

/1: Show CPU usage and FPS count/
#define LV_USE_PERF_MONITOR 0
#if LV_USE_PERF_MONITOR
#define LV_USE_PERF_MONITOR_POS LV_ALIGN_BOTTOM_RIGHT
#endif

/*1: Show the used memory and the memory fragmentation

Requires LV_MEM_CUSTOM = 0*/
#define LV_USE_MEM_MONITOR 0
#if LV_USE_MEM_MONITOR
#define LV_USE_MEM_MONITOR_POS LV_ALIGN_BOTTOM_LEFT
#endif

/1: Draw random colored rectangles over the redrawn areas/
#define LV_USE_REFR_DEBUG 0

/Change the built in (v)snprintf functions/
#define LV_SPRINTF_CUSTOM 0
#if LV_SPRINTF_CUSTOM
#define LV_SPRINTF_INCLUDE <stdio.h>
#define lv_snprintf snprintf
#define lv_vsnprintf vsnprintf
#else /LV_SPRINTF_CUSTOM/
#define LV_SPRINTF_USE_FLOAT 0
#endif /LV_SPRINTF_CUSTOM/

#define LV_USE_USER_DATA 1

/*Garbage Collector settings
Used if lvgl is bound to higher level language and the memory is managed by that language/
#define LV_ENABLE_GC 0
#if LV_ENABLE_GC != 0
#define LV_GC_INCLUDE “gc.h” /Include Garbage Collector related things/
#endif /LV_ENABLE_GC/

/*=====================

COMPILER SETTINGS
====================/

/For big endian systems set to 1/
#define LV_BIG_ENDIAN_SYSTEM 0

/Define a custom attribute to lv_tick_inc function/
#define LV_ATTRIBUTE_TICK_INC

/Define a custom attribute to lv_timer_handler function/
#define LV_ATTRIBUTE_TIMER_HANDLER

/Define a custom attribute to lv_disp_flush_ready function/
#define LV_ATTRIBUTE_FLUSH_READY

/Required alignment size for buffers/
#define LV_ATTRIBUTE_MEM_ALIGN_SIZE 1

/*Will be added where memories needs to be aligned (with -Os data might not be aligned to boundary by default).

E.g. attribute((aligned(4)))*/
#define LV_ATTRIBUTE_MEM_ALIGN

/Attribute to mark large constant arrays for example font’s bitmaps/
#define LV_ATTRIBUTE_LARGE_CONST

/Compiler prefix for a big array declaration in RAM/
#define LV_ATTRIBUTE_LARGE_RAM_ARRAY

/Place performance critical functions into a faster memory (e.g RAM)/
#define LV_ATTRIBUTE_FAST_MEM

/Prefix variables that are used in GPU accelerated operations, often these need to be placed in RAM sections that are DMA accessible/
#define LV_ATTRIBUTE_DMA

/*Export integer constant to binding. This macro is used with constants in the form of LV_ that
should also appear on LVGL binding API such as Micropython./
#define LV_EXPORT_CONST_INT(int_value) struct _silence_gcc_warning /The default value just prevents GCC warning/

/Extend the default -32k…32k coordinate range to -4M…4M by using int32_t for coordinates instead of int16_t/
#define LV_USE_LARGE_COORD 0

/*==================

FONT USAGE
===================/

/*Montserrat fonts with ASCII range and some symbols using bpp = 4
*https://fonts.google.com/specimen/Montserrat*/
#define LV_FONT_MONTSERRAT_8 0
#define LV_FONT_MONTSERRAT_10 0
#define LV_FONT_MONTSERRAT_12 0
#define LV_FONT_MONTSERRAT_14 1
#define LV_FONT_MONTSERRAT_16 0
#define LV_FONT_MONTSERRAT_18 0
#define LV_FONT_MONTSERRAT_20 0
#define LV_FONT_MONTSERRAT_22 0
#define LV_FONT_MONTSERRAT_24 0
#define LV_FONT_MONTSERRAT_26 0
#define LV_FONT_MONTSERRAT_28 0
#define LV_FONT_MONTSERRAT_30 0
#define LV_FONT_MONTSERRAT_32 0
#define LV_FONT_MONTSERRAT_34 0
#define LV_FONT_MONTSERRAT_36 0
#define LV_FONT_MONTSERRAT_38 0
#define LV_FONT_MONTSERRAT_40 0
#define LV_FONT_MONTSERRAT_42 0
#define LV_FONT_MONTSERRAT_44 0
#define LV_FONT_MONTSERRAT_46 0
#define LV_FONT_MONTSERRAT_48 1

/Demonstrate special features/
#define LV_FONT_MONTSERRAT_12_SUBPX 0
#define LV_FONT_MONTSERRAT_28_COMPRESSED 0 /bpp = 3/
#define LV_FONT_DEJAVU_16_PERSIAN_HEBREW 0 /Hebrew, Arabic, Persian letters and all their forms/
#define LV_FONT_SIMSUN_16_CJK 0 /1000 most common CJK radicals/

/Pixel perfect monospace fonts/
#define LV_FONT_UNSCII_8 0
#define LV_FONT_UNSCII_16 0

/*Optionally declare custom fonts here.
*You can use these fonts as default font too and they will be available globally.
E.g. #define LV_FONT_CUSTOM_DECLARE LV_FONT_DECLARE(my_font_1) LV_FONT_DECLARE(my_font_2)/
#define LV_FONT_CUSTOM_DECLARE

/Always set a default font/
#define LV_FONT_DEFAULT &lv_font_montserrat_14

/*Enable handling large font and/or fonts with a lot of characters.
*The limit depends on the font size, font face and bpp.
Compiler error will be triggered if a font needs it./
#define LV_FONT_FMT_TXT_LARGE 1

/Enables/disables support for compressed fonts./
#define LV_USE_FONT_COMPRESSED 0

/Enable subpixel rendering/
#define LV_USE_FONT_SUBPX 0
#if LV_USE_FONT_SUBPX
/Set the pixel order of the display. Physical order of RGB channels. Doesn’t matter with “normal” fonts./
#define LV_FONT_SUBPX_BGR 0 /0: RGB; 1:BGR order/
#endif

/Enable drawing placeholders when glyph dsc is not found/
#define LV_USE_FONT_PLACEHOLDER 1

/*=================

TEXT SETTINGS
=================/
Select a character encoding for strings.
Your IDE or editor should have the same character encoding
- LV_TXT_ENC_UTF8
- LV_TXT_ENC_ASCII
  */
  #define LV_TXT_ENC LV_TXT_ENC_UTF8

/Can break (wrap) texts on these chars/
#define LV_TXT_BREAK_CHARS " ,.;:-_"

/*If a word is at least this long, will break wherever “prettiest”
To disable, set to a value <= 0/
#define LV_TXT_LINE_BREAK_LONG_LEN 0

/*Minimum number of characters in a long word to put on a line before a break.
Depends on LV_TXT_LINE_BREAK_LONG_LEN./
#define LV_TXT_LINE_BREAK_LONG_PRE_MIN_LEN 3

/*Minimum number of characters in a long word to put on a line after a break.
Depends on LV_TXT_LINE_BREAK_LONG_LEN./
#define LV_TXT_LINE_BREAK_LONG_POST_MIN_LEN 3

/The control character to use for signalling text recoloring./
#define LV_TXT_COLOR_CMD “#”

/*Support bidirectional texts. Allows mixing Left-to-Right and Right-to-Left texts.
*The direction will be processed according to the Unicode Bidirectional Algorithm:
*https://www.w3.org/International/articles/inline-bidi-markup/uba-basics*/
#define LV_USE_BIDI 0
#if LV_USE_BIDI
/*Set the default direction. Supported values:
*LV_BASE_DIR_LTR Left-to-Right
*LV_BASE_DIR_RTL Right-to-Left
LV_BASE_DIR_AUTO detect texts base direction/
#define LV_BIDI_BASE_DIR_DEF LV_BASE_DIR_AUTO
#endif

/*Enable Arabic/Persian processing
In these languages characters should be replaced with an other form based on their position in the text/
#define LV_USE_ARABIC_PERSIAN_CHARS 0

/*==================

WIDGET USAGE
================/

/*Documentation of the widgets: https://docs.lvgl.io/latest/en/html/widgets/index.html*/

#define LV_USE_ARC 1

#define LV_USE_BAR 1

#define LV_USE_BTN 1

#define LV_USE_BTNMATRIX 1

#define LV_USE_CANVAS 1

#define LV_USE_CHECKBOX 1

#define LV_USE_DROPDOWN 1 /Requires: lv_label/

#define LV_USE_IMG 1 /Requires: lv_label/

#define LV_USE_LABEL 1
#if LV_USE_LABEL
#define LV_LABEL_TEXT_SELECTION 1 /Enable selecting text of the label/
#define LV_LABEL_LONG_TXT_HINT 1 /Store some extra info in labels to speed up drawing of very long texts/
#endif

#define LV_USE_LINE 1

#define LV_USE_ROLLER 1 /Requires: lv_label/
#if LV_USE_ROLLER
#define LV_ROLLER_INF_PAGES 7 /Number of extra “pages” when the roller is infinite/
#endif

#define LV_USE_SLIDER 1 /Requires: lv_bar/

#define LV_USE_SWITCH 1

#define LV_USE_TEXTAREA 1 /Requires: lv_label/
#if LV_USE_TEXTAREA != 0
#define LV_TEXTAREA_DEF_PWD_SHOW_TIME 1500 /ms/
#endif

#define LV_USE_TABLE 1

/*==================

EXTRA COMPONENTS
==================/

/*-----------

Widgets
----------/
#define LV_USE_ANIMIMG 1

#define LV_USE_CALENDAR 1
#if LV_USE_CALENDAR
#define LV_CALENDAR_WEEK_STARTS_MONDAY 0
#if LV_CALENDAR_WEEK_STARTS_MONDAY
#define LV_CALENDAR_DEFAULT_DAY_NAMES {“Mo”, “Tu”, “We”, “Th”, “Fr”, “Sa”, “Su”}
#else
#define LV_CALENDAR_DEFAULT_DAY_NAMES {“Su”, “Mo”, “Tu”, “We”, “Th”, “Fr”, “Sa”}
#endif

#define LV_CALENDAR_DEFAULT_MONTH_NAMES {"January", "February", "March",  "April", "May",  "June", "July", "August", "September", "October", "November", "December"}
#define LV_USE_CALENDAR_HEADER_ARROW 1
#define LV_USE_CALENDAR_HEADER_DROPDOWN 1

#endif /LV_USE_CALENDAR/

#define LV_USE_CHART 1

#define LV_USE_COLORWHEEL 1

#define LV_USE_IMGBTN 1

#define LV_USE_KEYBOARD 1

#define LV_USE_LED 1

#define LV_USE_LIST 1

#define LV_USE_MENU 1

#define LV_USE_METER 1

#define LV_USE_MSGBOX 1

#define LV_USE_SPAN 1
#if LV_USE_SPAN
/*A line text can contain maximum num of span descriptor */
#define LV_SPAN_SNIPPET_STACK_SIZE 64
#endif

#define LV_USE_SPINBOX 1

#define LV_USE_SPINNER 1

#define LV_USE_TABVIEW 1

#define LV_USE_TILEVIEW 1

#define LV_USE_WIN 1

/*-----------

Themes
----------/

/A simple, impressive and very complete theme/
#define LV_USE_THEME_DEFAULT 1
#if LV_USE_THEME_DEFAULT

/*0: Light mode; 1: Dark mode*/
#define LV_THEME_DEFAULT_DARK 0

/*1: Enable grow on press*/
#define LV_THEME_DEFAULT_GROW 1

/*Default transition time in [ms]*/
#define LV_THEME_DEFAULT_TRANSITION_TIME 80

#endif /LV_USE_THEME_DEFAULT/

/A very simple theme that is a good starting point for a custom theme/
#define LV_USE_THEME_BASIC 1

/A theme designed for monochrome displays/
#define LV_USE_THEME_MONO 1

/*-----------

Layouts
----------/

/A layout similar to Flexbox in CSS./
#define LV_USE_FLEX 1

/A layout similar to Grid in CSS./
#define LV_USE_GRID 1

/*---------------------

3rd party libraries
--------------------/

/*File system interfaces for common APIs */

/API for fopen, fread, etc/
#define LV_USE_FS_STDIO 0
#if LV_USE_FS_STDIO
#define LV_FS_STDIO_LETTER ‘\0’ /Set an upper cased letter on which the drive will accessible (e.g. ‘A’)/
#define LV_FS_STDIO_PATH “” /Set the working directory. File/directory paths will be appended to it./
#define LV_FS_STDIO_CACHE_SIZE 0 />0 to cache this number of bytes in lv_fs_read()/
#endif

/API for open, read, etc/
#define LV_USE_FS_POSIX 0
#if LV_USE_FS_POSIX
#define LV_FS_POSIX_LETTER ‘\0’ /Set an upper cased letter on which the drive will accessible (e.g. ‘A’)/
#define LV_FS_POSIX_PATH “” /Set the working directory. File/directory paths will be appended to it./
#define LV_FS_POSIX_CACHE_SIZE 0 />0 to cache this number of bytes in lv_fs_read()/
#endif

/API for CreateFile, ReadFile, etc/
#define LV_USE_FS_WIN32 0
#if LV_USE_FS_WIN32
#define LV_FS_WIN32_LETTER ‘\0’ /Set an upper cased letter on which the drive will accessible (e.g. ‘A’)/
#define LV_FS_WIN32_PATH “” /Set the working directory. File/directory paths will be appended to it./
#define LV_FS_WIN32_CACHE_SIZE 0 />0 to cache this number of bytes in lv_fs_read()/
#endif

/API for FATFS (needs to be added separately). Uses f_open, f_read, etc/
#define LV_USE_FS_FATFS 0
#if LV_USE_FS_FATFS
#define LV_FS_FATFS_LETTER ‘\0’ /Set an upper cased letter on which the drive will accessible (e.g. ‘A’)/
#define LV_FS_FATFS_CACHE_SIZE 0 />0 to cache this number of bytes in lv_fs_read()/
#endif

/PNG decoder library/
#define LV_USE_PNG 1

/BMP decoder library/
#define LV_USE_BMP 0

/* JPG + split JPG decoder library.

Split JPG is a custom format optimized for embedded systems. */
#define LV_USE_SJPG 0

/GIF decoder library/
#define LV_USE_GIF 1

/QR code library/
#define LV_USE_QRCODE 0

/FreeType library/
#define LV_USE_FREETYPE 0
#if LV_USE_FREETYPE
/Memory used by FreeType to cache characters [bytes] (-1: no caching)/
#define LV_FREETYPE_CACHE_SIZE (16 * 1024)
#if LV_FREETYPE_CACHE_SIZE >= 0
/* 1: bitmap cache use the sbit cache, 0:bitmap cache use the image cache. /
/ sbit cache:it is much more memory efficient for small bitmaps(font size < 256) /
/ if font size >= 256, must be configured as image cache /
#define LV_FREETYPE_SBIT_CACHE 0
/ Maximum number of opened FT_Face/FT_Size objects managed by this cache instance. /
/ (0:use system defaults) */
#define LV_FREETYPE_CACHE_FT_FACES 0
#define LV_FREETYPE_CACHE_FT_SIZES 0
#endif
#endif

/Rlottie library/
#define LV_USE_RLOTTIE 0

/*FFmpeg library for image decoding and playing videos
Supports all major image formats so do not enable other image decoder with it/
#define LV_USE_FFMPEG 0
#if LV_USE_FFMPEG
/Dump input information to stderr/
#define LV_FFMPEG_DUMP_FORMAT 0
#endif

/*-----------

Others
----------/

/1: Enable API to take snapshot for object/
#define LV_USE_SNAPSHOT 0

/1: Enable Monkey test/
#define LV_USE_MONKEY 0

/1: Enable grid navigation/
#define LV_USE_GRIDNAV 0

/1: Enable lv_obj fragment/
#define LV_USE_FRAGMENT 0

/*1: Support using images as font in label or span widgets */
#define LV_USE_IMGFONT 0

/*1: Enable a published subscriber based messaging system */
#define LV_USE_MSG 0

/1: Enable Pinyin input method/
/Requires: lv_keyboard/
#define LV_USE_IME_PINYIN 0
#if LV_USE_IME_PINYIN
/1: Use default thesaurus/
/If you do not use the default thesaurus, be sure to use lv_ime_pinyin after setting the thesauruss/
#define LV_IME_PINYIN_USE_DEFAULT_DICT 1
/Set the maximum number of candidate panels that can be displayed/
/This needs to be adjusted according to the size of the screen/
#define LV_IME_PINYIN_CAND_TEXT_NUM 6

/*Use 9 key input(k9)*/
#define LV_IME_PINYIN_USE_K9_MODE      1
#if LV_IME_PINYIN_USE_K9_MODE == 1
    #define LV_IME_PINYIN_K9_CAND_TEXT_NUM 3
#endif // LV_IME_PINYIN_USE_K9_MODE

#endif

/*==================

EXAMPLES
==================/

/Enable the examples to be built with the library/
#define LV_BUILD_EXAMPLES 1

/*===================

DEMO USAGE
====================*/

/*Show some widget. It might be required to increase LV_MEM_SIZE */
#define LV_USE_DEMO_WIDGETS 1
#if LV_USE_DEMO_WIDGETS
#define LV_DEMO_WIDGETS_SLIDESHOW 0
#endif

/Demonstrate the usage of encoder and keyboard/
#define LV_USE_DEMO_KEYPAD_AND_ENCODER 0

/Benchmark your system/
#define LV_USE_DEMO_BENCHMARK 0
#if LV_USE_DEMO_BENCHMARK
/Use RGB565A8 images with 16 bit color depth instead of ARGB8565/
#define LV_DEMO_BENCHMARK_RGB565A8 0
#endif

/Stress test for LVGL/
#define LV_USE_DEMO_STRESS 0

/Music player demo/
#define LV_USE_DEMO_MUSIC 0
#if LV_USE_DEMO_MUSIC
#define LV_DEMO_MUSIC_SQUARE 0
#define LV_DEMO_MUSIC_LANDSCAPE 0
#define LV_DEMO_MUSIC_ROUND 0
#define LV_DEMO_MUSIC_LARGE 0
#define LV_DEMO_MUSIC_AUTO_PLAY 0
#endif

/–END OF LV_CONF_H–/

#endif /LV_CONF_H/

#endif /End of “Content enable”/emphasized text

And here is the test code which is changing the 2 pictures, could anyone have a hint here?
lv_init();
/* Linux frame buffer device init */
fbdev_init();

/* A small buffer for LittlevGL to draw the screen's content */
static lv_color_t buf[DISP_BUF_SIZE];

/*Initialize a descriptor for the buffer*/
static lv_disp_draw_buf_t disp_buf;
lv_disp_draw_buf_init(&disp_buf, buf, NULL, DISP_BUF_SIZE);


/*Initialize and register a display driver*/
static lv_disp_drv_t disp_drv;
lv_disp_drv_init(&disp_drv);
disp_drv.draw_buf   = &disp_buf;

// disp_drv.full_refresh = 1;
disp_drv.flush_cb = fbdev_flush;
disp_drv.hor_res = 1280;
disp_drv.ver_res = 800;
disp_drv.sw_rotate = 1; // add for rotation
disp_drv.rotated = LV_DISP_ROT_90;
// disp_drv.full_refresh = 1;

lv_disp_drv_register(&disp_drv);

pthread_t testFun = 0;
int ret = pthread_create(&testFun, NULL, testFunction, &ret);
if (ret != 0)
{
		//	cout << "pthread_create error" << endl;
		printf("pthread_create_tidTestFun error\r\n");
		return -1;
}
pthread_detach(testFun);

void testFunction(void *arg)
{

while(1)
    {
        sleep(2);
        lv_img_set_src(bk_img, &test2);
        lv_obj_align(bk_img, LV_ALIGN_CENTER, 0, 0);

        sleep(2);

        lv_img_set_src(bk_img, &test1);
        lv_obj_align(bk_img, LV_ALIGN_CENTER, 0, 0);
            
        }

}