[esp_lcd](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/lcd.html) supports RGB interfaced LCD panel, with a frame buffer managed by the driver itself.
This example shows the general process of installing an RGB panel driver, and displays a scatter chart on the screen based on the LVGL library. For more information about porting the LVGL library, please refer to [another lvgl porting example](../i80_controller/README.md).
## How to use the example
### Hardware Required
* An ESP development board, which has RGB LCD peripheral supported and PSRAM onboard
* A general RGB panel, 16 bit-width, with HSYNC, VSYNC and DE signal
* An USB cable for power supply and programming
### Hardware Connection
The connection between ESP Board and the LCD is as follows:
```
ESP Board RGB Panel
+-----------------------+ +-------------------+
| GND +--------------+GND |
| | | |
| 3V3 +--------------+VCC |
| | | |
| PCLK+--------------+PCLK |
| | | |
| DATA[15:0]+--------------+DATA[15:0] |
| | | |
| HSYNC+--------------+HSYNC |
| | | |
| VSYNC+--------------+VSYNC |
| | | |
| DE+--------------+DE |
| | | |
| BK_LIGHT+--------------+BLK |
+-----------------------+ | |
3V3-----+DISP_EN |
| |
+-------------------+
```
The GPIO number used by this example can be changed in [lvgl_example_main.c](main/rgb_lcd_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/rgb_lcd_example_main.c).
If the RGB LCD panel only supports DE mode, you can bypass the `HSYNC` and `VSYNC` signals, by assigning `EXAMPLE_PIN_NUM_HSYNC` and `EXAMPLE_PIN_NUM_VSYNC` with `-1`.
### Build and Flash
Run `idf.py -p PORT build flash monitor` to build, flash and monitor the project. A scatter chart 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 (731) spiram: Reserving pool of 32K of internal memory for DMA/internal allocations
* Check the backlight's turn-on level, and update it in `EXAMPLE_LCD_BK_LIGHT_ON_LEVEL`
* No memory for frame buffer
* The frame buffer of RGB panel is located in ESP side (unlike other controller based LCDs, where the frame buffer is located in external chip). As the frame buffer usually consumes much RAM (depends on the LCD resolution and color depth), we recommend to put the frame buffer into PSRAM (like what we do in this example). However, putting frame buffer in PSRAM will limit the PCLK to around 12MHz (due to the bandwidth of PSRAM).
