STM32

LVGL Can be added to STM32CubeIDE in a similar fashion to any other Eclipse-based IDE.

Including LVGL in a Project

  • Create or open a project in STM32CubeIDE.

  • Copy the entire LVGL folder to [project_folder]/Drivers/lvgl.

  • In the STM32CubeIDE Project Explorer pane: right click on the LVGL folder that you copied (you may need to refresh the view first before it will appear), and select Add/remove include path…. If this doesn't appear, or doesn't work, you can review your project include paths under the Project -> Properties menu, and then navigating to C/C++ Build -> Settings -> Include paths, and ensuring that the LVGL directory is listed.

Now that the source files are included in your project, follow the instructions to Add LVGL to Your Project and to create the lv_conf.h file, and initialise the display.

Bare Metal Example

A minimal example using STM32CubeIDE, and HAL. * When setting up Pinout and Configuration using the Device Configuration Tool, select System Core -> SYS and ensure that Timebase Source is set to SysTick. * Configure any other peripherals (including the LCD panel), and initialise them in main.c. * #include "lvgl.h" in the main.c file. * Create some frame buffer(s) as global variables:

/* Frame buffers
 * Static or global buffer(s). The second buffer is optional
 * TODO: Adjust color format and choose buffer size. DISPLAY_WIDTH * 10 is one suggestion. */
#define BYTES_PER_PIXEL (LV_COLOR_FORMAT_GET_SIZE(LV_COLOR_FORMAT_RGB565)) /* will be 2 for RGB565 */
#define BUFF_SIZE (DISPLAY_WIDTH * 10 * BYTES_PER_PIXEL)
static uint8_t buf_1[BUFF_SIZE];
static uint8_t buf_2[BUFF_SIZE];
  • In your main() function, after initialising your CPU,

    peripherals, and LCD panel, call lv_init() to initialise LVGL. You can then create the display driver using lv_display_create(), and register the frame buffers using lv_display_set_buffers().

    //Initialise LVGL UI library
lv_init();

lv_display_t * disp = lv_display_create(WIDTH, HEIGHT); /* Basic initialization with horizontal and vertical resolution in pixels */
lv_display_set_flush_cb(disp, my_flush_cb); /* Set a flush callback to draw to the display */
lv_display_set_buffers(disp, buf_1, buf_2, sizeof(buf_1), LV_DISPLAY_RENDER_MODE_PARTIAL); /* Set an initialized buffer */

  • Create some dummy Widgets to test the output:

    /* Change Active Screen's background color */
lv_obj_set_style_bg_color(lv_screen_active(), lv_color_hex(0x003a57), LV_PART_MAIN);
lv_obj_set_style_text_color(lv_screen_active(), lv_color_hex(0xffffff), LV_PART_MAIN);

/* Create a spinner */
lv_obj_t * spinner = lv_spinner_create(lv_screen_active(), 1000, 60);
lv_obj_set_size(spinner, 64, 64);
lv_obj_align(spinner, LV_ALIGN_BOTTOM_MID, 0, 0);

  • Add a call to lv_timer_handler() inside your while(1) loop:

    /* Infinite loop */
while (1)
{
    lv_timer_handler();
    HAL_Delay(5);
}

  • Add a call to lv_tick_inc() inside the SysTick_Handler() function. Open the stm32xxxx_it.c file (the name will depend on your specific MCU), and update the SysTick_Handler() function:

    void SysTick_Handler(void)
{
    /* USER CODE BEGIN SysTick_IRQn 0 */

    HAL_SYSTICK_IRQHandler();
    lv_tick_inc(1);
    #ifdef USE_RTOS_SYSTICK
        osSystickHandler();
    #endif

    /* USER CODE END SysTick_IRQn 0 */
    HAL_IncTick();
    /* USER CODE BEGIN SysTick_IRQn 1 */

    /* USER CODE END SysTick_IRQn 1 */
}

  • Finally, write the callback function, my_flush_cb, which will send the display buffer to your LCD panel. Below is one example, but it will vary depending on your setup.

    void my_flush_cb(lv_display_t * disp, const lv_area_t * area, lv_color_t * color_p)
{
    //Set the drawing region
    set_draw_window(area->x1, area->y1, area->x2, area->y2);

    int height = area->y2 - area->y1 + 1;
    int width = area->x2 - area->x1 + 1;

    //We will do the SPI write manually here for speed
    HAL_GPIO_WritePin(DC_PORT, DC_PIN, GPIO_PIN_SET);
    //CS low to begin data
    HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_RESET);

    //Write colour to each pixel
    for (int i = 0; i < width * height; i++) {
        uint16_t color_full = (color_p->red << 11) | (color_p->green << 5) | (color_p->blue);
        parallel_write(color_full);

        color_p++;
    }

    //Return CS to high
    HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_SET);

    /* IMPORTANT!!!
     * Inform the graphics library that you are ready with the flushing */
    lv_display_flush_ready(disp);
}

FreeRTOS Example

A minimal example using STM32CubeIDE, HAL, and CMSISv1 (FreeRTOS). Note that we have not used Mutexes in this example, however LVGL is NOT thread safe and so Mutexes should be used. See: Threading Considerations * #include "lvgl.h" * Create your frame buffer(s) as global variables:

/* Frame buffers
 * Static or global buffer(s). The second buffer is optional */
#define BYTES_PER_PIXEL (LV_COLOR_FORMAT_GET_SIZE(LV_COLOR_FORMAT_RGB565)) /* will be 2 for RGB565 */
/* TODO: Declare your own BUFF_SIZE appropriate to your system. */
static lv_color_t buf_1[BUFF_SIZE];
#define BUFF_SIZE (DISPLAY_WIDTH * 10 * BYTES_PER_PIXEL)
static uint8_t buf_1[BUFF_SIZE];
static lv_color_t buf_2[BUFF_SIZE];

  • In your main function, after your peripherals (SPI, GPIOs, LCD etc) have been initialised, initialise LVGL using lv_init(), create a new display driver using lv_display_create(), and register the frame buffers using lv_display_set_buffers().

    /* Initialise LVGL UI library */
lv_init();
lv_display_t *display = lv_display_create(WIDTH, HEIGHT); /* Create the display */
lv_display_set_flush_cb(display, my_flush_cb);            /* Set a flush callback to draw to the display */
lv_display_set_buffers(disp, buf_1, buf_2, sizeof(buf_1), LV_DISPLAY_RENDER_MODE_PARTIAL); /* Set an initialized buffer */

/* Register the touch controller with LVGL - Not included here for brevity. */

  • Create some dummy Widgets to test the output:

    /* Change Active Screen's background color */
lv_obj_set_style_bg_color(lv_screen_active(), lv_color_hex(0x003a57), LV_PART_MAIN);
lv_obj_set_style_text_color(lv_screen_active(), lv_color_hex(0xffffff), LV_PART_MAIN);

/* Create a spinner */
lv_obj_t * spinner = lv_spinner_create(lv_screen_active(), 1000, 60);
lv_obj_set_size(spinner, 64, 64);
lv_obj_align(spinner, LV_ALIGN_BOTTOM_MID, 0, 0);

  • Create two threads to call lv_timer_handler(), and lv_tick_inc().You will need two osThreadId handles for CMSISv1. These don't strictly have to be globally accessible in this case, however STM32Cube code generation does by default. If you are using CMSIS and STM32Cube code generation it should look something like this:

    //Thread Handles
osThreadId lvgl_tickHandle;
osThreadId lvgl_timerHandle;

/* definition and creation of lvgl_tick */
osThreadDef(lvgl_tick, LVGLTick, osPriorityNormal, 0, 1024);
lvgl_tickHandle = osThreadCreate(osThread(lvgl_tick), NULL);

//LVGL update timer
osThreadDef(lvgl_timer, LVGLTimer, osPriorityNormal, 0, 1024);
lvgl_timerHandle = osThreadCreate(osThread(lvgl_timer), NULL);

  • And create the thread functions:

    /* LVGL timer for tasks. */
void LVGLTimer(void const * argument)
{
  for(;;)
  {
    lv_timer_handler();
    osDelay(20);
  }
}
/* LVGL tick source */
void LVGLTick(void const * argument)
{
  for(;;)
  {
    lv_tick_inc(10);
    osDelay(10);
  }
}

  • Finally, create the my_flush_cb function to output the frame buffer to your LCD. The specifics of this function will vary depending on which MCU features you are using. Below is an example for a typical MCU interface.

    void my_flush_cb(lv_display_t * display, const lv_area_t * area, uint8_t * px_map);
{
  uint16_t * color_p = (uint16_t *)px_map;

  //Set the drawing region
  set_draw_window(area->x1, area->y1, area->x2, area->y2);

  int height = area->y2 - area->y1 + 1;
  int width = area->x2 - area->x1 + 1;

  //Begin SPI Write for DATA
  HAL_GPIO_WritePin(DC_PORT, DC_PIN, GPIO_PIN_SET);
  HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_RESET);

  //Write colour to each pixel
  for (int i = 0; i < width * height; i++) {
      parallel_write(color_p);
      color_p++;
  }

  //Return CS to high
  HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_SET);

  /* IMPORTANT!!!
   * Inform the graphics library that you are ready with the flushing */
  lv_display_flush_ready(display);
}

DMA2D Support

LVGL supports DMA2D - a feature of some STM32 MCUs which can improve performance when blending fills and images. Some STM32 product lines such as STM32F4 STM32F7, STM32L4, STM32U5, and STM32H7 include models with DMA2D support.

LVGL's integration with DMA2D can be enabled by setting LV_USE_DRAW_DMA2D to 1 in lv_conf.h

With LV_USE_DRAW_DMA2D_INTERRUPT set to 0 and LV_USE_OS set to LV_OS_NONE, DMA2D will draw some fills and images concurrently with the software render where possible. If LV_USE_DRAW_DMA2D_INTERRUPT is set to 1 and LV_USE_OS set to LV_OS_FREERTOS (or another OS) the main difference will be that the core will idle instead of "busywait" while waiting for a DMA2D transfer to complete.

If LV_USE_DRAW_DMA2D_INTERRUPT is enabled then you are required to call lv_draw_dma2d_transfer_complete_interrupt_handler whenever the DMA2D "transfer complete" global interrupt is received.

If your STM device has a NeoChrom GPU, you can use the Nema GFX renderer instead.