{"id":14976,"date":"2023-07-14T09:45:46","date_gmt":"2023-07-14T04:15:46","guid":{"rendered":"https:\/\/fastbitlab.com\/?p=14976"},"modified":"2023-10-20T17:25:18","modified_gmt":"2023-10-20T11:55:18","slug":"ltdc-layer-testing-on-hardware-set-background-color","status":"publish","type":"post","link":"https:\/\/fastbitlab.com\/blog\/ltdc-layer-testing-on-hardware-set-background-color\/","title":{"rendered":"STM32-LTDC, LCD-TFT, LVGL(MCU3) Lecture 41| LTDC layer testing on hardware"},"content":{"rendered":"
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LTDC layer testing on hardware<\/span><\/strong><\/h1>\n
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The term “LTDC layer” typically refers to the Layered Timing Controller (LTDC) in embedded systems, particularly in microcontrollers and display driver circuits. LTDC is responsible for managing the timing and control signals for driving an LCD (Liquid Crystal Display) or TFT (Thin-Film Transistor) display.<\/span><\/p>\n

The LTDC layer acts as an interface between the microcontroller and the display panel. It receives pixel data from the microcontroller and converts it into the necessary control signals for the display. These control signals include horizontal and vertical synchronization signals, pixel clocks, data enable signals, and control signals for backlight control, if applicable.<\/span><\/p>\n

The LTDC layer typically provides features such as resolution scaling, pixel formatting, color space conversion, and blending of multiple layers. It allows the microcontroller to control the display parameters, such as refresh rate, color depth, and display orientation.<\/span><\/p>\n

By utilizing the LTDC layer, developers can efficiently drive and control displays in embedded systems, providing graphical user interfaces, animations, and other visual content. The layer facilitates the seamless integration of displays into various applications, including automotive dashboards, medical devices, industrial control systems, and more.<\/span><\/p>\n

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Now, we will set a background color for our frame buffer. The frame buffer is located in the bsp_lcd_ex.c file and its size is determined by FB_SIZE. <\/span>So, based on the pixel format you have chosen in the bsp_lcd.h. <\/span><\/span><\/p>\n

uint8_t bsp_fb[FB_SIZE];<\/strong><\/span><\/p>\n

#include<\/span> \"bsp_lcd.h\"\r\n\r\n#if<\/span> BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB565\r\n   #define<\/span> FB_SIZE (BSP_FB_WIDTH * BSP_FB_HEIGHT * 2)\r\n#elif<\/span> BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB666\r\n   #define<\/span> FB_SIZE ((BSP_FB_WIDTH * BSP_FB_HEIGHT * 2) + ((BSP_FB_WIDTH * BSP_FB_HEIGHT *2)\/8U)+1U)\r\n#elif<\/span> BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB888\r\n   #define<\/span> FB_SIZE (BSP_FB_WIDTH * BSP_FB_HEIGHT * 3)\r\n#else<\/span>\r\n    #error<\/span>\"Select pixel format\"<\/span>\r\n#endif<\/span>\r\n\r\nuint8_t<\/span> bsp_fb[FB_SIZE<\/span>];<\/strong>\r\n\r\n<\/pre>\n
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Set the background color:<\/b><\/span><\/p>\n
The background color is usually defined in the frame buffer as a pixel value. Each pixel is represented by a certain number of bits, where each bit determines the color of a specific component (e.g., red, green, blue, and alpha). The number of bits per component and the organization of the frame buffer depend on your display configuration and pixel format.<\/span><\/p>\n
Look at below, which displays a function called set_fb_background_color. To utilize this function, you need to provide an RGB888 value as input. The function internally performs a conversion to RGB565 based on the pixel format. Currently, only this particular conversion is supported. However, you have the option to implement additional conversions if needed. To set the desired color, simply invoke this function with the appropriate color parameter.<\/span><\/p>\n
void<\/span> bsp_lcd_set_fb_background_color(uint32_t<\/span> rgb888)\r\n{\r\n#if<\/span>(BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB565)\r\n     write_to_fb_rgb565((uint16_t*<\/span>)bsp_fb,(FB_SIZE\/2U),Convert_RGB888_to_RGB565(rgb888));\r\n#elif<\/span>(BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB666)\r\n     write_to_fb_rgb666(Convert_RGB888_to_RGB666(rgb888));\r\n#elif<\/span>(BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB888)\r\n     write_to_fb_rgb888(rgb888);\r\n#else<\/span>\r\n         #error<\/span>\"Select pixel format\"<\/span>\r\n#endif<\/span>\r\n}<\/pre>\n
void bsp_lcd_set_fb_background_color(uint32_t rgb888)<\/b><\/span><\/p>\n
This is the function declaration for setting the background color of the frame buffer. It takes an input <\/span>rgb888<\/span> which represents the desired color in RGB888 format (8 bits per color channel).<\/span><\/span><\/p>\n
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#if(BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB565)<\/b><\/span><\/p>\n
write_to_fb_rgb565((uint16_t*)bsp_fb,(FB_SIZE\/2U, Convert_RGB888_to_RGB565(rgb888));<\/b><\/span><\/p>\n
#elif(BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_RGB666)<\/b><\/span><\/p>\n
write_to_fb_rgb666(Convert_RGB888_to_RGB666(rgb888));<\/b><\/span><\/p>\n
#elif(BSP_LCD_PIXEL_FMT == BSP_LCD_PIXEL_FMT_rgb888)<\/b><\/span><\/p>\n
write_to_fb_rgb888(rgb888));<\/b><\/span><\/p>\n
This code snippet uses preprocessor directives (<\/span>#if<\/span>, <\/span>#elif<\/span>, <\/span>#else<\/span>, <\/span>#endif<\/span>) to conditionally execute different code based on the selected pixel format (<\/span>BSP_LCD_PIXEL_FMT<\/span>). It assumes three possible pixel formats: RGB565, RGB666, and rgb888.<\/span><\/span><\/p>\n