LittlevGL - Free Open-source Embedded GUI Library

LittlevGL provides everything you need to create a Graphical User Interface (GUI) on embedded systems with easy-to-use graphical elements, beautiful visual effects and low memory footprint.

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Website · Live demo · Simulator · Docs · Blog

Features

• 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 encoding
• Fully customizable graphical elements
• Hardware independent to use with any microcontroller or display
• Scalable to operate with little memory (64 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

Supported devices

Basically, every modern controller - which is able to drive a display - is suitable to run LittlevGL. The minimal requirements:

• 16, 32 or 64-bit microcontroller or processor
• > 16 MHz clock speed
• > 8 kB RAM for static data and > 2 KB RAM for dynamic data (graphical objects)
• > 64 kB flash program memory
• Optionally ~1/10 screen sized memory for buffered drawing (on 240 × 320, 16-bit colors it's 15 kB)

Just to mention some platforms:

• STM32F1, STM32F3, STM32F4, STM32F7
• Microchip dsPIC33, PIC24, PIC32MX, PIC32MZ
• NXP Kinetis, LPC, iMX
• Linux frame buffer (/dev/fb)
• Raspberry PI
• Espressif ESP32
• Nordic nrf52
• Quectell M66

Quick start in a simulator

Try LittlevGL in a simulator on you PC without any embedded hardware. Choose a project with your favourite IDE:

Eclipse	CodeBlock	Visual Studio	PlatfomIO	Qt Creator
Cross-platform with SDL	Native Windows	Cross-platform with SDL	Cross-platform with SDL	Cross-platform with SDL

Porting to an embedded hardware

In the most simple case you need to do these steps:

1. Copy lv_conf_templ.h as lv_conf.h next to lvgl and set at least LV_HOR_RES, LV_VER_RES and LV_COLOR_DEPTH.
2. Call lv_tick_inc(x) every x milliseconds in a Timer or Task (x should be between 1 and 10)
3. Call lv_init()
4. Register a function which can copy a pixel array to an area of the screen:

lv_disp_drv_t disp_drv;               /*Descriptor of a display driver*/
lv_disp_drv_init(&disp_drv);          /*Basic initialization*/
disp_drv.disp_flush = disp_flush;     /*Set your driver function*/
lv_disp_drv_register(&disp_drv);      /*Finally register the driver*/
    
void disp_flush(int32_t x1, int32_t y1, int32_t x2, int32_t y2, const lv_color_t * color_p)
{
    int32_t x, y;
    for(y = y1; y <= y2; y++) {
        for(x = x1; x <= x2; x++) {
            sep_pixel(x, y, *color_p);  /* Put a pixel to the display.*/
            color_p++;
        }
    }

    lv_flush_ready();                  /* Tell you are ready with the flushing*/
}
    

5. Register a function which can read an input device. E.g. for a touch pad:

lv_indev_drv_init(&indev_drv);             /*Descriptor of a input device driver*/
indev_drv.type = LV_INDEV_TYPE_POINTER;    /*Touch pad is a pointer-like device*/
indev_drv.read = touchpad_read;            /*Set your driver function*/
lv_indev_drv_register(&indev_drv);         /*Finally register the driver*/

bool touchpad_read(lv_indev_data_t * data)
{
    static lv_coord_t last_x = 0;
    static lv_coord_t last_y = 0;

    /*Save the state and save the pressed cooridnate*/
    data->state = touchpad_is_pressed() ? LV_INDEV_STATE_PR : LV_INDEV_STATE_REL; 
    if(data->state == LV_INDEV_STATE_PR) touchpad_get_xy(&last_x, &last_y);
   
    /*Set the coordinates (if released use the last pressed cooridantes)*/
    data->point.x = last_x;
    data->point.y = last_y;

    return false; /*Return `false` because we are not buffering and no more data to read*/
}

6. Call lv_task_handler() periodically every few milliseconds.

For a detailed description check the Online documatation or the Porting tutorial

Code examples

Create a button with a label and assign a click callback

lv_obj_t * btn = lv_btn_create(lv_scr_act(), NULL);     /*Add a button the current screen*/
lv_obj_set_pos(btn, 10, 10);                            /*Set its position*/
lv_obj_set_size(btn, 100, 50);                          /*Set its size*/

lv_btn_set_action(btn, LV_BTN_ACTION_CLICK, btn_action);/*Assign a callback to the button*/
lv_obj_t * label = lv_label_create(btn, NULL);          /*Add a label to the button*/
lv_label_set_text(label, "Button");                     /*Set the labels text*/

lv_res_t btn_action(lv_obj_t * btn)
{
    printf("Clicked\n");
    return LV_RES_OK;
}

Modify the styles

static lv_style_t style_btn_rel;                        /*A variable to store the released style*/
lv_style_copy(&style_btn_rel, &lv_style_plain);         /*Initialize from a built-in style*/
style_btn_rel.body.border.color = LV_COLOR_HEX3(0x269);
style_btn_rel.body.border.width = 1;
style_btn_rel.body.main_color = LV_COLOR_HEX3(0xADF);
style_btn_rel.body.grad_color = LV_COLOR_HEX3(0x46B);
style_btn_rel.body.shadow.width = 4;
style_btn_rel.body.shadow.type = LV_SHADOW_BOTTOM;
style_btn_rel.body.radius = LV_RADIUS_CIRCLE;
style_btn_rel.text.color = LV_COLOR_HEX3(0xDEF);

static lv_style_t style_btn_pr;                         /*A variable to store the pressed style*/
lv_style_copy(&style_btn_pr, &style_btn_rel);           /*Initialize from a built-in style*/
style_btn_pr.body.border.color = LV_COLOR_HEX3(0x46B);
style_btn_pr.body.main_color = LV_COLOR_HEX3(0x8BD);
style_btn_pr.body.grad_color = LV_COLOR_HEX3(0x24A);
style_btn_pr.body.shadow.width = 2;
style_btn_pr.text.color = LV_COLOR_HEX3(0xBCD);

lv_btn_set_style(btn, LV_BTN_STYLE_REL, &style_btn_rel);    /*Set the buton's released style*/
lv_btn_set_style(btn, LV_BTN_STYLE_PR, &style_btn_pr);      /*Set the buton's pressed style*/

Enable a fancy effect

/*Add some effects when the button is clicked*/
lv_btn_set_ink_in_time(btn, 300);
lv_btn_set_ink_wait_time(btn, 100);
lv_btn_set_ink_out_time(btn, 300);

Check out the Documentation for more!

Contributing

To ask questions and discuss topics we use GitHub's Issue tracker. You contribute in several ways:

• Answer other's question click the Watch button on the top to get notified about the issues
• Report and/or fix bugs using the issue tracker and in Pull-request
• Suggest and/or implement new features using the issue tracker and in Pull-request
• Improve and/or translate the documentation learn more here
• Write a blog post about your experiences learn more here
• Upload your project or product as a reference to this site

Before contributing, please read CONTRIBUTING.md.
For more info read this blog post.

Donate

If you are pleased with the library, found it useful, or you are happy with the support you got, please help its further development: