LVGL

Board Stm32F746GDISCOVERY

Has on-chip RAM: 340Kb, on-chip flash: 1Mb, on board external SDRAM: 128Mb, on board external flash: 128Mb, on board LCD-TFT: 480x272

Calculate bytes of memory an image consumes

Given:

  • Resolution of bitmap image: 480x270

  • Pixel format: ARG88888

bpp: bit per pixel

Total memory consumed = Width x Height x (bpp/8) = 480 x 270 x (32/8) = 506.25Kb

Bitmap image (BMP)

  • An BMP image contains uncompressed pixel data, so it consumes more space on disk.

  • You can directly read the pixel values and display them on the display module.

Select pixel format for your application

Depends on:

  • Pixel format support by the LCD driver chip

  • Desired color range

  • Microcontroller RAM space availability

  • Microcontroller Flash space availability

Porting library to STM32F746GDISCOVERY project

  1. Create project with board STM32F746GDISCOVERY, but do not enable all default peripherals.

  2. Set Debug to “Serial Wire”.

  3. Set High Speed Clock to “BYPASS Clock Source”, and Low Speed Clock to “Crystal/Ceramic Resonator”.

  4. Enable these peripherals: I2C3, USART1, LTDC.

  5. If you use external SDRAM, you need to enable FMC/SDRAM1, choose SDCKE0+SDNE0 in Clock and chip enable.

  6. Then go to tab Project Manager, choose Advanced Settings and untick Generate Code of these peripheral.

  7. In tab Clock Configuration, set HCLK up to 216, just type this number and press enter then Cubeide will calculate for you.

  8. Create source folder hal_stm_lvgl

  9. Clone sample project Stm32F746GDISCOVERY of LVGL github

  10. Copy the two folders tft and touchpad from hal_stm_lvgl, then paste them into hal_stm_lvgl source folder created earlier.

  11. Copy the two folders Components and STM32746G-Discovery from Utilities, then paste them into hal_stm_lvgl source folder created earlier.

  12. Add path to all folder above.

  13. Clone LVGL github.

  14. Copy lvgl cloned folder to your project.

  15. Move lv_conf_template.h out side lvgl folder, and rename it to lv_conf.h.

  16. Open lv_conf.h and change #if 0 to #if 1 to enable content in this file.

  17. Keep src folder, lv_version.h and lvgl.h. Delete all the rest files and folders.

  18. If you want to use example or demo, then keep demos and examples folder.

../../_images/project_tree_lvgl.png

Note

  1. When building the project, you may encounter some errors in certain files from the STM32746G-Discovery folder.

    This occurs because the peripheral is not enabled. Simply use #if 0 and #endif to temporarily disable that file.

  2. The most important thing that will cause the screen to become unresponsive is the missing call to the function lv_tick_inc(1).

    You have to call this function in void SysTick_Handler(void) of the stm32f7xx_it.c file.

  3. I recommend using LVGL version 8.2 for enhanced stability. Because cannot use macro rotation display in version 9.3.0

    If you use lvgl version 8.2, then you should use hal_stm_lvgl in here

Run lvgl example

/* USER CODE BEGIN Includes */
#include "lvgl/lvgl.h"
#include "lv_conf.h"
#include "tft.h"
#include "touchpad.h"
#include "lv_examples.h"

/* USER CODE END Includes */

int main(void)
{

/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

/* MCU Configuration--------------------------------------------------------*/

/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();

/* USER CODE BEGIN Init */

/* USER CODE END Init */

/* Configure the system clock */
SystemClock_Config();

/* USER CODE BEGIN SysInit */

/* USER CODE END SysInit */

/* Initialize all configured peripherals */
MX_GPIO_Init();
/* USER CODE BEGIN 2 */
/* Enable I-Cache */
SCB_EnableICache();

/* Enable D-Cache */
SCB_EnableDCache();

lv_init();
tft_init();
touchpad_init();

lv_example_dropdown_1();
/* USER CODE END 2 */

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
    HAL_Delay(5);
    lv_task_handler();
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}