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Supported Targets	ESP32-S3

RGB panel example

esp_lcd 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.

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.

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.

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 for full steps to configure and use ESP-IDF to build projects.

Example Output

...
I (0) cpu_start: Starting scheduler on APP CPU.
I (731) spiram: Reserving pool of 32K of internal memory for DMA/internal allocations
I (731) example: Turn off LCD backlight
I (731) gpio: GPIO[39]| InputEn: 0| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0
I (731) example: Install RGB panel driver
I (741) example: Turn on LCD backlight
I (741) example: Initialize LVGL library
I (741) example: Register display driver to LVGL
I (741) example: Install LVGL tick timer
I (741) example: Display LVGL Scatter Chart
...

Troubleshooting

Why the LCD doesn't light up?
- 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).
LCD screen drift
- Slow down the PCLK frequency
- Adjust other timing parameters like PCLK clock edge (by pclk_active_neg), sync porches like HBP (by hsync_back_porch) according to your LCD spec

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

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