esp-idf/examples/peripherals/lcd/lvgl/README.md
2021-09-13 15:08:48 +08:00

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| Supported Targets | ESP32 | ESP32-S2 | ESP32-S3 |
| ----------------- | ----- | -------- | -------- |
# LVGL porting example
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 [this main file](main/lvgl_example_main.c), and the UI demo code is located in [another single file](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
* 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 [lvgl_example_main.c](main/lvgl_example_main.c).
Especially, please pay attention to the level used to turn on the LCD backlight, some LCD module needs a low level to turn it on, while others take a high level. You can change the backlight level macro `EXAMPLE_LCD_BK_LIGHT_ON_LEVEL` in [lvgl_example_main.c](main/lvgl_example_main.c).
### Build and Flash
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
For any technical queries, please open an [issue] (https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you soon.