ESP32 移植开源图形库 LittlevGL
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LittlevGL 介绍
littlevGL is a free and open-source graphics library providing everything you need to create embedded GUI with easy-to-use graphical elements, beautiful visual effects and low memory footprint.
LittlevGL 官网链接
LittlevGL 移植教程
LittlevGL 官方文档
LittlevGL GitHub链接
关键特性：
- Powerful building blocks buttons, charts, lists, sliders, images etc
- Advanced graphics with animations, anti-aliasing, opacity, smooth scrolling
- Various input devices touch pad, mouse, keyboard, encoder, buttons etc
- Multi language support with UTF-8 decoding
- Fully customizable graphical elements
- Hardware independent to use with any microcontroller or display
- Scalable to operate with few memory (50 kB Flash, 10 kB RAM)
- OS, External memory and GPU supported but not required
- Single frame buffer operation even with advances graphical effects
- Written in C for maximal compatibility
- Simulator to develop on PC without embedded hardware
- Tutorials, examples, themes for rapid development
- Documentation and API references online
移植过程
- 在工程目录下新建一个 components 目录，放入 LittlevGL 源码
- 在 components 目录下新建一个 include 目录，放入 lv_conf.h 文件，由 LittlevGL 源码目录中的 lv_conf_templ.h文件而来
- 在 components 目录下新建一个 component.mk 文件，将 LittlevGL 相关源码添加到组件的
COMPONENT_SRCDIRS、COMPONENT_ADD_INCLUDEDIRS和COMPONENT_PRIV_INCLUDEDIRS目录变量中 - 之后在程序中使用了～，可根据 LittlevGL Tutorial在自己的主程序中实现
大致初始化流程：
/***********************
* Initialize LittlevGL
***********************/
lv_init();
/***********************
* Tick interface
***********************/
/* Initialize a Timer for 1 ms period and
* in its interrupt call
* lv_tick_inc(1); */
/***********************
* Display interface
***********************/
lv_disp_drv_t disp_drv; /*Descriptor of a display driver*/
lv_disp_drv_init(&disp_drv); /*Basic initialization*/
/*Set up the functions to access to your display*/
disp_drv.disp_flush = ex_disp_flush; /*Used in buffered mode (LV_VDB_SIZE != 0 in lv_conf.h)*/
disp_drv.disp_fill = ex_disp_fill; /*Used in unbuffered mode (LV_VDB_SIZE == 0 in lv_conf.h)*/
disp_drv.disp_map = ex_disp_map; /*Used in unbuffered mode (LV_VDB_SIZE == 0 in lv_conf.h)*/
/*Finally register the driver*/
lv_disp_drv_register(&disp_drv);
/*************************
* Input device interface
*************************/
/*Add a touchpad in the example*/
/*touchpad_init();*/ /*Initialize your touchpad*/
lv_indev_drv_t indev_drv; /*Descriptor of an input device driver*/
lv_indev_drv_init(&indev_drv); /*Basic initialization*/
indev_drv.type = LV_INDEV_TYPE_POINTER; /*The touchpad is pointer type device*/
indev_drv.read = ex_tp_read; /*Library ready your touchpad via this function*/
lv_indev_drv_register(&indev_drv); /*Finally register the driver*/
/*************************************
* Run the task handler of LittlevGL
*************************************/
/* Periodically call this function.
* The timing is not critical but should be between 1..10 ms */
lv_task_handler();
/*delay_ms(5)*/需要实现的函数：
/***********************
* Display interface
***********************/
/*Write the internal buffer (VDB) to the display. 'lv_flush_ready()' has to be called when finished*/
void (*disp_flush)(int32_t x1, int32_t y1, int32_t x2, int32_t y2, const lv_color_t * color_p);
/*Fill an area with a color on the display*/
void (*disp_fill)(int32_t x1, int32_t y1, int32_t x2, int32_t y2, lv_color_t color);
/*Write pixel map (e.g. image) to the display*/
void (*disp_map)(int32_t x1, int32_t y1, int32_t x2, int32_t y2, const lv_color_t * color_p);
/*************************
* Input device interface
*************************/
bool (*read)(lv_indev_data_t *data); /*Function pointer to read data. Return 'true' if there is still data to be read (buffered)*/注意：在实现
disp_flush函数时，在函数末尾需要调用 LittlevGL 提供的lv_flush_ready函数
上述的这些函数可以自行实现，函数体保持一致即可
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