| Supported Targets | ESP32 | ESP32-S2 | ESP32-S3 |
| ----------------- | ----- | -------- | -------- |
# LVGL porting example (based on i80 interfaced LCD controller)

LVGL is an open-source graphics library for creating modern GUIs. It has plenty of built-in graphical elements with low memory footprint, which is friendly for embedded GUI applications.

This example can be taken as a skeleton of porting the LVGL library onto the `esp_lcd` driver layer. **Note** that, this example only focuses on the display interface, regardless of the input device driver.

The whole porting code is located in [i80_controller_example_main.c](main/i80_controller_example_main.c), and the UI demo code is located in [lvgl_demo_ui.c](main/lvgl_demo_ui.c).

The UI will display two images (one Espressif logo and another Espressif text), which have been converted into C arrays by the [online converting tool](https://lvgl.io/tools/imageconverter), and will be compiled directly into application binary.

This example is constructed by [IDF component manager](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/tools/idf-component-manager.html), all the external dependency will be handled by the CMake build system automatically. In this case, it will help download the lvgl from [registry](https://components.espressif.com/component/lvgl/lvgl), with the version specified in the [manifest file](main/idf_component.yml).

This example uses the [esp_timer](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/esp_timer.html) to generate the ticks needed by LVGL. For more porting guides, please refer to [LVGL porting doc](https://docs.lvgl.io/master/porting/index.html).

## How to use the example

### Hardware Required

* An ESP development board
* An Intel 8080 interfaced (so called MCU interface or parallel interface) LCD (this example can use ST7789, NT35510 or ILI9341)
* An USB cable for power supply and programming

### Hardware Connection

The connection between ESP Board and the LCD is as follows:

```
   ESP Board                      LCD Screen
┌─────────────┐              ┌────────────────┐
│             │              │                │
│         3V3 ├─────────────►│ VCC            │
│             │              │                │
│         GND ├──────────────┤ GND            │
│             │              │                │
│  DATA[0..7] │◄────────────►│ DATA[0..7]     │
│             │              │                │
│        PCLK ├─────────────►│ PCLK           │
│             │              │                │
│          CS ├─────────────►│ CS             │
│             │              │                │
│         D/C ├─────────────►│ D/C            │
│             │              │                │
│         RST ├─────────────►│ RST            │
│             │              │                │
│    BK_LIGHT ├─────────────►│ BCKL           │
│             │              │                │
└─────────────┘              └────────────────┘
```

The GPIO number used by this example can be changed in [i80_controller_example_main.c](main/i80_controller_example_main.c).
Especially, please pay attention to the binary signal level used to turn the LCD backlight on, some LCD modules need a low level to turn it on, while others require a high level. You can change the backlight level macro `EXAMPLE_LCD_BK_LIGHT_ON_LEVEL` in [i80_controller_example_main.c](main/i80_controller_example_main.c).

### Build and Flash

Run `idf.py set-target <target-name>` to select one supported target that can run this example. This step will also apply the default Kconfig configurations into the `sdkconfig` file.

Run `idf.py menuconfig` to open a terminal UI where you can tune specific configuration for this example in the `Example Configuration` menu.

* `i80 LCD controller model`: Choose the LCD model to use by the example. If you choose `NT35510`, there will be another relevant configuration `NT35510 Data Width`, to choose the data line width for your NT35510 LCD module.

* `Allocate color data from PSRAM`: Select this option if you want to allocate the LVGL draw buffers from PSRAM.

Run `idf.py -p PORT build flash monitor` to build, flash and monitor the project. A fancy animation will show up on the LCD as expected.

The first time you run `idf.py` for the example will cost extra time as the build system needs to address the component dependencies and downloads the missing components from registry into `managed_components` folder.

(To exit the serial monitor, type ``Ctrl-]``.)

See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.

### Example Output

```bash
I (0) cpu_start: Starting scheduler on APP CPU.
I (418) example: Turn off LCD backlight
I (418) gpio: GPIO[2]| InputEn: 0| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0
I (428) example: Initialize Intel 8080 bus
I (438) example: Install LCD driver of st7789
I (558) example: Turn on LCD backlight
I (558) example: Initialize LVGL library
I (558) example: Register display driver to LVGL
I (558) example: Install LVGL tick timer
I (558) example: Display LVGL animation
```


## Troubleshooting

* Can't get a stable UI when `EXAMPLE_LCD_I80_COLOR_IN_PSRAM` is enabled.

   This is because of the limited PSRAM bandwidth, compared to the internal SRAM. You can either decrease the PCLK clock `EXAMPLE_LCD_PIXEL_CLOCK_HZ` in [i80_controller_example_main.c](main/i80_controller_example_main.c) or increase the PSRAM working frequency `SPIRAM_SPEED` from the KConfig (e.g. **ESP32S3-Specific** -> **Set RAM clock speed**) or decrease the FPS in LVGL configuration. For illustration, this example has set the refresh period to 100ms in the default sdkconfig file.

For any technical queries, please open an [issue] (https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you soon.