# Zephyr — LVGL documentation

# Zephyr

## What is Zephyr?

Zephyr is an open source real-time operating system (RTOS) that is easy to deploy, secure, connect and manage. It has a growing set of software libraries that can be used across various applications and industry sectors such as Industrial IoT, wearables, machine learning and more. Zephyr is built with an emphasis on broad chipset support, security, dependability, longterm support releases and a growing open source ecosystem.

### Highlights of Zephyr

- Small - Runs on microcontrollers as small as 8 kB Flash and 5 kB of RAM.

- Scalable - Usable for complex multicore systems.

- Customizable - Out-of-the-box support for 500+ boards and high portability.

- Secure - Built with safety and security in mind, offers Long-term support.

- Ecosystem - Zephyr not only provides the RTOS kernel but also developer tooling, device drivers, connectivity, logging, tracing, power management and much more.

- Decoupling - Leverages devicetree to describe and configure the target system.

- Compliant - Apps are runnable as native Linux applications, which simplifies debugging and profiling.

## How to run LVGL on Zephyr?

To setup your development environment refer to the getting started guide.

After you completed the setup above you can check out all of the provided samples for various boards. You can check the list of available boards using:

    $ west boards

After you chose a board you can build one of the LVGL demos for it. Here we are using the `native_posix` board, which allows for running the application on your posix compliant host system:

    $ west build -b native_posix samples/modules/lvgl/demos

To run the application on your host:

    $ west build -t run

In case you chose any of the other supported boards you can flash to the device with:

    $ west flash

If you want to build any of the other demo applications check out the samples README.

## Leveraging Zephyr Features

### Shell

Zephyr includes a powerful shell implementation that can be enabled with the Kconfig symbols `CONFIG_SHELL` and `CONFIG_LV_Z_SHELL` (the demos from above have it enabled by default).

The shell offers enabling/disabling of LVGL monkeys:

    # Create a new monkey with the given indev type
    uart$ lvgl monkey create [pointer|keypad|button|encoder]

    # Enable/Disable a monkey
    uart$ lvgl monkey set <index> <inactive/active>

This is useful for checking your application for memory leaks and other bugs. Speaking of memory leaks, you can also acquire stats of the memory used by LVGL

    uart$ lvgl stats memory

For more details refer to the shell documentation.

### Devicetree

Zephyr uses the devicetree description language to create and manage LVGL input devices.

The pseudo device binding descriptions can be found at:

- button input

- pointer input

- encoder input

Essentially those buffer the `input_event` generated by the device pointed to by the `input` phandle or if left empty the binding captures all events regardless of the source. You do not have to instantiate or manage the devices yourself, they are created at application start up before `main()` is executed.

Most boards or shields that have a display or display connector have the pointer input device already declared:

    lvgl_pointer {
        compatible = "zephyr,lvgl-pointer-input";
        input = <&ft5336_touch>;
    };

You can access the underlying lvgl `lv_indev_t` for configuration. Example with the encoder device to assign a `lv_group_t`:

    const struct device *lvgl_encoder = DEVICE_DT_GET(DT_COMPAT_GET_ANY_STATUS_OKAY(zephyr_lvgl_encoder_input));

    lv_obj_t *arc;
    lv_group_t *arc_group;

    arc = lv_arc_create(lv_screen_active());
    lv_obj_align(arc, LV_ALIGN_CENTER, 0, 0);
    lv_obj_set_size(arc, 150, 150);

    arc_group = lv_group_create();
    lv_group_add_obj(arc_group, arc);
    lv_indev_set_group(lvgl_input_get_indev(lvgl_encoder), arc_group);

### Kconfig

Aside from enabling the shell you can also use Kconfig to finetune the footprint of your application.

    # Size of the memory region from which lvgl memory is allocated
    CONFIG_LV_Z_MEM_POOL_SIZE=8192

    # Do not include every widget/theme by default, enable them as needed.
    CONFIG_LV_CONF_MINIMAL=y

Overlays can be used to enable/disable features for specific boards or build targets. For more information refer to the application development guide.

## Where can I find more information?

- Zephyr Documentation: Zephyr Documentation

- Zephyr mailing list: Zepyhr Mailing List

- Zephyr Discord server: Zepyhr Discord server