LittlevGL - 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.
---
- [Features](#features)
- [Supported devices](#supported-devices)
- [Quick start in a simulator](#quick-start-in-a-simulator)
- [Add LittlevGL to your project](#add-littlevgl-to-your-project)
- [Learn the basics](#learn-the-basics)
- [Examples](#examples)
- [Contributing](#contributing)
- [Donate](#donate)
## Features
* **Powerful building blocks** buttons, charts, lists, sliders, images, etc.
* **Advanced graphics** with animations, anti-aliasing, opacity, smooth scrolling
* **Simultaneously use various input devices** touchscreen, mouse, keyboard, encoder, buttons, etc.
* **Simultaneously use multiple displays** i.e. monochrome and color display
* **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
* **Micropython Binding** exposes [LittlevGL API in Micropython](https://blog.littlevgl.com/2019-02-20/micropython-bindings)
* **Simulator** to develop on PC without embedded hardware
* **Tutorials, examples, themes** for rapid development
* **Documentation** and API references
## 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 is recommended
- Flash/ROM: > 64 kB for the very essential components (> 180 kB is recommended)
- RAM:
- Static RAM usage: ~8..16 kB depending on the used features and objects types
- Stack: > 2kB (> 4 kB is recommended)
- Dynamic data (heap): > 4 KB (> 16 kB is recommended if using several objects).
Set by `LV_MEM_SIZE` in *lv_conf.h*.
- Display buffer: > *"Horizontal resolution"* pixels (> 10 × *"Horizontal resolution"* is recommended)
- C99 or newer compiler
*Note that the memory usage might vary depending on the architecture, compiler and build options.*
Just to mention some **platforms**:
- STM32F1, STM32F3, [STM32F4](https://blog.littlevgl.com/2017-07-15/stm32f429_disco_port), [STM32F7](https://github.com/littlevgl/stm32f746_disco_no_os_sw4stm32)
- Microchip dsPIC33, PIC24, PIC32MX, PIC32MZ
- NXP Kinetis, LPC, iMX
- [Linux frame buffer](https://blog.littlevgl.com/2018-01-03/linux_fb) (/dev/fb)
- [Raspberry PI](http://www.vk3erw.com/index.php/16-software/63-raspberry-pi-official-7-touchscreen-and-littlevgl)
- [Espressif ESP32](https://github.com/littlevgl/esp32_ili9431)
- Nordic nrf52
- Quectell M66
## Quick start in a simulator
The easiest way to get started with LittlevGL is to run it in a simulator on your PC without any embedded hardware.
Choose a project with your favourite IDE:
| Eclipse | CodeBlocks | Visual Studio | PlatformIO | Qt Creator |
|-------------|-------------|---------------|-----------|------------|
| [](https://github.com/littlevgl/pc_simulator_sdl_eclipse) | [](https://github.com/littlevgl/pc_simulator_win_codeblocks) | [](https://github.com/littlevgl/visual_studio_2017_sdl_x64) | [](https://github.com/littlevgl/pc_simulator_sdl_platformio) | [](https://blog.littlevgl.com/2019-01-03/qt-creator) |
| Cross-platform
with SDL
(Recommended on
Linux and Mac) | Native Windows | Windows
with SDL | Cross-platform
with SDL | Cross-platform
with SDL |
## Add LittlevGL to your project
The steps below show how to setup LittlevGL on an embedded system with a display and a touchpad.
You can use the [Simulators](https://docs.littlevgl.com/en/html/get-started/pc-simulator) to get ready to use projects which can be run on your PC.
1. [Download](https://littlevgl.com/download) or [Clone](https://github.com/littlevgl/lvgl) the library
2. Copy the `lvgl` folder into your project
3. Copy `lvgl/lv_conf_template.h` as `lv_conf.h` next to the `lvgl` folder and set at least `LV_HOR_RES_MAX`, `LV_VER_RES_MAX` and `LV_COLOR_DEPTH`.
4. Include `lvgl/lvgl.h` where you need to use LittlevGL related functions.
5. 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.
6. Call `lv_init()`
7. Create a display buffer for LittlevGL
```c
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*/
```
8. Implement and register a function which can **copy a pixel array** to an area of your display:
```c
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; /*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(lv_disp_t * disp, const lv_area_t * area, lv_color_t * color_p)
{
int32_t x, y;
for(y = area->y1; y <= area->y2; y++) {
for(x = area->x1; x <= area->x2; x++) {
set_pixel(x, y, *color_p); /* Put a pixel to the display.*/
color_p++;
}
}
lv_disp_flush_ready(disp); /* Indicate you are ready with the flushing*/
}
```
9. Implement and register a function which can **read an input device**. E.g. for a touch pad:
```c
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_cb = my_touchpad_read; /*Set your driver function*/
lv_indev_drv_register(&indev_drv); /*Finally register the driver*/
bool my_touchpad_read(lv_indev_drv_t * indev_driver, 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 coordinate*/
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 coordinates)*/
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*/
}
```
10. Call `lv_task_handler()` periodically every few milliseconds in the main `while(1)` loop, in Timer interrupt or in an Operation system task.
It will redraw the screen if required, handle input devices etc.
## Learn the basics
### Objects (Widgets)
The graphical elements like Buttons, Labels, Sliders, Charts etc are called objects in LittelvGL. Go to [Object types](https://docs.littlevgl.com/en/html/object-types/index) to see the full list of available types.
Every object has a parent object. The child object moves with the parent and if you delete the parent the children will be deleted too. Children can be visible only on their parent.
The *screen* are the "root" parents. To get the current screen call `lv_scr_act()`.
You can create a new object with `lv__create(parent, obj_to_copy)`. It will return an `lv_obj_t *` variable which should be used as a reference to the object to set its parameters.
The first parameter is the desired *parent*, te second parameters can be an object to copy (`NULL` is unused).
For example:
```c
lv_obj_t * slider1 = lv_slider_create(lv_scr_act(), NULL);
```
To set some basic attribute `lv_obj_set_(obj, )` function can be used. For example:
```c
lv_obj_set_x(btn1, 30);
lv_obj_set_y(btn1, 10);
lv_obj_set_size(btn1, 200, 50);
```
The objects has type specific parameters too which can be set by `lv__set_(obj, )` functions. For example:
```c
lv_slider_set_value(slider1, 70, LV_ANIM_ON);
```
To see the full API visit the documentation of the object types or the related header file (e.g. `lvgl/src/lv_objx/lv_slider.h`).
### Styles
Styles can be assigned to the objects to changed their appearance. A style describes the appearance of rectangle-like objects (like a button or slider), texts, images and lines at once.
You can create a new style like this:
```c
static lv_style_t style1; /*Declare a new style. Should be `static`*/
lv_style_copy(&style1, &lv_style_plain); /*Copy a built-in style*/
style1.body.main_color = LV_COLOR_RED; /*Main color*/
style1.body.grad_color = lv_color_hex(0xffd83c) /*Gradient color (orange)*/
style1.body.radius = 3;
style1.text.color = lv_color_hex3(0x0F0) /*Label color (green)*/
style1.text.font = &lv_font_dejavu_22; /*Change font*/
...
```
To set a new style for an object use the `lv_set_style(obj, LV__STYLE_, &my_style)` functions. For example:
```c
lv_slider_set_style(slider1, LV_SLIDER_STYLE_BG, &slider_bg_style);
lv_slider_set_style(slider1, LV_SLIDER_STYLE_INDIC, &slider_indic_style);
lv_slider_set_style(slider1, LV_SLIDER_STYLE_KNOB, &slider_knob_style);
```
If an object's style is `NULL` then it will inherit its parent's style. For example, the labels' style are `NULL` by default. If you place them on a button then they will use the `style.text` properties from the button's style.
Learn more in [Style overview](https://docs.littlevgl.com/en/html/overview/style) section.
### Events
Events are used to inform the user if something has happened with an object. You can assign a callback to an object which will be called if the object is clicked, released, dragged, being deleted etc. It should look like this:
```c
lv_obj_set_event_cb(btn, btn_event_cb); /*Assign a callback to the button*/
...
void btn_event_cb(lv_obj_t * btn, lv_event_t event)
{
if(event == LV_EVENT_CLICKED) {
printf("Clicked\n");
}
}
```
Learn more about the events in the [Event overview](https://docs.littlevgl.com/en/html/overview/event) section.
## Examples
### Button with label
```c
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_obj_set_event_cb(btn, btn_event_cb); /*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*/
...
void btn_event_cb(lv_obj_t * btn, lv_event_t event)
{
if(event == LV_EVENT_CLICKED) {
printf("Clicked\n");
}
}
```
### Button with styles
Add styles to the previously button from the previous example
```c
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 the released 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 button's released style*/
lv_btn_set_style(btn, LV_BTN_STYLE_PR, &style_btn_pr); /*Set the button's pressed style*/
```
### Slider and object alignment
```c
lv_obj_t * label;
...
/* Create a slider in the center of the display */
lv_obj_t * slider = lv_slider_create(lv_scr_act(), NULL);
lv_obj_set_width(slider, 200); /*Set the width*/
lv_obj_align(slider, NULL, LV_ALIGN_CENTER, 0, 0); /*Align to the center of the parent (screen)*/
lv_obj_set_event_cb(slider, slider_event_cb); /*Assign an event function*/
/* Create a label below the slider */
label = lv_label_create(lv_scr_act(), NULL);
lv_label_set_text(label, "0");
lv_obj_set_auto_realign(slider, true);
lv_obj_align(label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
...
void slider_event_cb(lv_obj_t * slider, lv_event_t event)
{
if(event == LV_EVENT_VALUE_CHANGED) {
static char buf[4]; /* max 3 bytes for number plus 1 null terminating byte */
snprintf(buf, 4, "%u", lv_slider_get_value(slider));
lv_label_set_text(slider_label, buf); /*Refresh the text*/
}
}
```
### List and themes
```c
/*Texts of the list elements*/
const char * txts[] = {"First", "Second", "Third", "Forth", "Fifth", "Sixth", NULL};
/* Initialize and set a theme. `LV_THEME_NIGHT` needs to enabled in lv_conf.h. */
lv_theme_t * th = lv_theme_night_init(20, NULL);
lv_theme_set_current(th);
/*Create a list*/
lv_obj_t* list = lv_list_create(lv_scr_act(), NULL);
lv_obj_set_size(list, 120, 180);
lv_obj_set_pos(list, 10, 10);
/*Add buttons*/
uint8_t i;
for(i = 0; txts[i]; i++) {
lv_obj_t * btn = lv_list_add_btn(list, LV_SYMBOL_FILE, txts[i]);
lv_obj_set_event_cb(btn, list_event); /*Assign event function*/
lv_btn_set_toggle(btn, true); /*Enable on/off states*/
}
/* Initialize and set an other theme. `LV_THEME_MATERIAL` needs to enabled in lv_conf.h.
* If `LV_TEHE_LIVE_UPDATE 1` then the previous list's style will be updated too.*/
th = lv_theme_material_init(210, NULL);
lv_theme_set_current(th);
/*Create an other list*/
list = lv_list_create(lv_scr_act(), NULL);
lv_obj_set_size(list, 120, 180);
lv_obj_set_pos(list, 150, 10);
/*Add buttons with the same texts*/
for(i = 0; txts[i]; i++) {
lv_obj_t * btn = lv_list_add_btn(list, LV_SYMBOL_FILE, txts[i]);
lv_obj_set_event_cb(btn, list_event);
lv_btn_set_toggle(btn, true);
}
...
static void list_event(lv_obj_t * btn, lv_event_t e)
{
if(e == LV_EVENT_CLICKED) {
printf("%s\n", lv_list_get_btn_text(btn));
}
}
```
### Use LittlevGL from Micropython
Learn more about [Micropython](https://docs.littlevgl.com/en/html/get-started/micropython).
```python
# Create a Button and a Label
scr = lv.obj()
btn = lv.btn(scr)
btn.align(lv.scr_act(), lv.ALIGN.CENTER, 0, 0)
label = lv.label(btn)
label.set_text("Button")
# Load the screen
lv.scr_load(scr)
```
## Contributing
To ask questions please use the [Forum](https://forum.littlevgl.com).
For development-related things (bug reports, feature suggestions) use [GitHub's Issue tracker](https://github.com/littlevgl/lvgl/issues).
If you are interested in contributing to LittlevGL you can
- **Help others** in the [Forum](https://forum.littlevgl.com).
- **Inspire people** by speaking about your project in [My project](https://forum.littlevgl.com/c/my-projects) category in the Forum or add it to the [References](https://blog.littlevgl.com/2018-12-26/references) post
- **Improve and/or translate the documentation.** Go to the [Documentation](https://github.com/littlevgl/docs) repository to learn more
- **Write a blog post** about your experiences. See how to do it in the [Blog](https://github.com/littlevgl/blog) repository
- **Report and/or fix bugs** in [GitHub's issue tracker](https://github.com/littlevgl/lvgl/issues)
- **Help in the developement**. Check the [Open issues](https://github.com/littlevgl/lvgl/issues) especially the ones with [Help wanted](https://github.com/littlevgl/lvgl/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22) label and tell your ideas about a topic or implement a feature.
It should be useful to read the
- [Contributing guide](https://blog.littlevgl.com/2018-12-06/contributing)
- [Coding style guide](https://github.com/littlevgl/lvgl/blob/master/docs/CODING_STYLE.md)
## 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:
[](https://littlevgl.com/donate)