LVGL and DISCO-H747I in mbed studio

12th May, 2021

The goal for this project is to use the LVGL library in mbed studio. Firstly study the blog: How start with the LVGL on the Disco F746NG with Mbed.

Setup a New Program as described in the above blog.

Add the libraries as shown in the photo:

mbed documentation: Importing a library.

BSP_DISCO_H747I.

lvgl v7.11.0.

lv_drivers v7.11.0.

lv_examples v7.11.0.

mbed-os 6.7.0 Shared.

Setup the lvgl library: here are the modifications to my two files:

    /**
 * @file lv_conf.h
 * Configuration file for v7.6.0-dev
 */

/*
 * COPY THIS FILE AS `lv_conf.h` NEXT TO the `lvgl` FOLDER
 */

#if 1 /*Set it to "1" to enable content kg1*/

#ifndef LV_CONF_H
#define LV_CONF_H
/* clang-format off */

#include <stdint.h>   //kg1

/*====================
   Graphical settings
 *====================*/

/* Maximal horizontal and vertical resolution to support by the library.*/
#define LV_HOR_RES_MAX          (800)
#define LV_VER_RES_MAX          (480)

/* Color depth:
 * - 1:  1 byte per pixel
 * - 8:  RGB332
 * - 16: RGB565
 * - 32: ARGB8888
 */
#define LV_COLOR_DEPTH     32  //kg1
...
    
    

    /**
 * @file lv_ex_conf.h
 * Configuration file for v7.5.0
 *
 */
/*
 * COPY THIS FILE AS lv_ex_conf.h
 */

#if 1 /*Set it to "1" to enable the content kg1*/

#ifndef LV_EX_CONF_H
#define LV_EX_CONF_H


/*******************
 * GENERAL SETTING
 *******************/
#define LV_EX_PRINTF       0       /*Enable printf-ing data in demoes and examples*/
#define LV_EX_KEYBOARD     0       /*Add PC keyboard support to some examples (`lv_drivers` repository is required)*/
#define LV_EX_MOUSEWHEEL   0       /*Add 'encoder' (mouse wheel) support to some examples (`lv_drivers` repository is required)*/

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

/*Show some widget*/
#define LV_USE_DEMO_WIDGETS        1  //kg1
#if LV_USE_DEMO_WIDGETS
#define LV_DEMO_WIDGETS_SLIDESHOW  0
#endif
...
    
    

main.cpp setting:

    #include "mbed.h"
#include "lvgl/lvgl.h"
#include "BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery.h"
#include "BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery_lcd.h"
#include "BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery_ts.h"
#include "lv_examples/lv_examples.h"

#define LVGL_TICK 5                             //Time tick value for lvgl in ms (1-10msa)
#define TICKER_TIME 5ms //0.001 * LVGL_TICK           //modified to miliseconds
 
Ticker ticker;                                  //Initialize your system tick                    
TS_StateTypeDef TS_State;  
 
void lv_ticker_func();
void display_init(void);
void touchpad_init(void);
static void my_disp_flush_cb(lv_disp_drv_t* disp_drv, const lv_area_t* area, lv_color_t* color_p);
static bool touchpad_read(lv_indev_drv_t *indev, lv_indev_data_t *data);
 
int main()
{
    printf("LittlevGL DEMO");
    display_init();
    touchpad_init();
    ticker.attach(callback(&lv_ticker_func),TICKER_TIME);
 
     lv_demo_widgets();
 
    while(1);
}
 
void lv_ticker_func(){
    lv_tick_inc(LVGL_TICK); 
    //Call lv_tick_inc(x) every x milliseconds in a Timer or Task (x should be between 1 and 10). 
    //It is required for the internal timing of LittlevGL.
    lv_task_handler(); 
    //Call lv_task_handler() periodically every few milliseconds. 
    //It will redraw the screen if required, handle input devices etc.
}
 
void display_init(void){
    //Init the touch screen display via the BSP driver. Based on ST's example.
    BSP_LCD_Init();
    BSP_LCD_LayerDefaultInit(0, LCD_FB_START_ADDRESS);
    BSP_LCD_DisplayOn();
    BSP_LCD_SelectLayer(0);
    BSP_LCD_Clear(LCD_COLOR_TRANSPARENT );
    BSP_LCD_SetFont(&LCD_DEFAULT_FONT);
    BSP_LCD_SetBackColor(LCD_COLOR_WHITE);
    BSP_LCD_SetTextColor(LCD_COLOR_DARKBLUE);
    
    lv_init();                                  //Initialize the LittlevGL
    static lv_disp_buf_t disp_buf;
    static lv_color_t buf[LV_HOR_RES_MAX * 10]; //Declare a buffer for 10 lines                                                              
    lv_disp_buf_init(&disp_buf, buf, NULL, LV_HOR_RES_MAX * 10); //Initialize the display buffer
    
    //Implement and register a function which can copy a pixel array to an area of your display
    lv_disp_drv_t disp_drv;                     //Descriptor of a display driver
    lv_disp_drv_init(&disp_drv);                //Basic initialization
    disp_drv.flush_cb = my_disp_flush_cb;       //Set your driver function
    disp_drv.buffer = &disp_buf;                //Assign the buffer to the display
    lv_disp_drv_register(&disp_drv);            //Finally register the driver
}
 
void my_disp_flush_cb(lv_disp_drv_t* disp_drv, const lv_area_t* area, lv_color_t* color_p)
{
    //The most simple case (but also the slowest) to put all pixels to the screen one-by-one
    uint16_t x, y;
    for(y = area->y1; y <= area->y2; y++) {
        for(x = area->x1; x <= area->x2; x++) {
            //put_px(x, y, *color_p)
            BSP_LCD_DrawPixel( x, y, color_p->full);
            color_p++;
        }
    }
    //IMPORTANT!!!* Inform the graphics library that you are ready with the flushing
    lv_disp_flush_ready(disp_drv);
}
 
 
void touchpad_init(void){
    BSP_TS_Init(480, 272);
    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_cb = touchpad_read;              //Set the touchpad_read function
    lv_indev_drv_register(&indev_drv);              //Register touch driver in LvGL
}
 
static bool touchpad_read(lv_indev_drv_t *indev, lv_indev_data_t *data){
    // Read your touchpad
    BSP_TS_GetState(&TS_State);
    if(TS_State.touchDetected) {
        data->point.x = TS_State.touchX[0];
        data->point.y = TS_State.touchY[0];
        data->state = LV_INDEV_STATE_PR;
    } else {
        data->point.x = 0;
        data->point.y = 0;
        data->state = LV_INDEV_STATE_REL;
    }
    return false;   //false: no more data to read because we are no buffering
}
    
    

Copy and paste the above code into main.cpp in mbed studio.

You are now ready to compile your demo code:

I hope this works for you!