# LCD

## Introduction

ESP chips can generate various kinds of timings needed by common LCDs on the market, like SPI LCD, I2C LCD, Parallel LCD (Intel 8080), RGB/SRGB LCD, MIPI DSI LCD and etc. The `esp_lcd` component offers an abstracted driver framework to support them in a unified way.

An LCD typically consists of two main planes:

- Control Plane: This plane allows us to read and write to the internal registers of the LCD device controller. Host typically uses this plane for tasks such as initializing the LCD power supply and performing gamma calibration.

- Data Plane: The data plane is responsible for transmitting pixel data to the LCD device.

## Functional Overview

In the context of `esp_lcd`, both the data plane and the control plane are represented by the `esp_lcd_panel_handle_t` type.

On some LCDs, these two planes may be combined into a single plane. In this configuration, pixel data is transmitted through the control plane, achieving functionality similar to that of the data plane. This merging is common in SPI LCDs and I2C LCDs. Additionally, there are LCDs that do not require a separate control plane. For instance, certain RGB LCDs automatically execute necessary initialization procedures after power-up. Host devices only need to continuously refresh pixel data through the data plane. However, it's essential to note that not all RGB LCDs eliminate the control plane entirely. Some LCD devices can simultaneously support multiple interfaces, requiring the host to send specific commands via the control plane (such as those based on the SPI interface) to enable the RGB mode.

This document will discuss how to create the control plane and data plane, as mentioned earlier, based on different types of LCDs.

备注

ESP-IDF provides only a limited number of LCD device controller drivers out of the box (e.g., ST7789), more drivers are available in the Espressif Component Registry.

## LCD Control Panel Operations

- `esp_lcd_panel_reset()` can reset the LCD control panel.

- `esp_lcd_panel_init()` performs a basic initialization of the control panel. To perform more manufacture specific initialization, please refer to Steps to Add Manufacture Specific Initialization.

- By combining using `esp_lcd_panel_swap_xy()` and `esp_lcd_panel_mirror()`, you can achieve the functionality of rotating or mirroring the LCD screen.

- `esp_lcd_panel_disp_on_off()` can turn on or off the LCD screen by cutting down the output path from the frame buffer to the LCD screen. Please note, this is not controlling the LCD backlight. Backlight control is not covered by the `esp_lcd` driver.

- `esp_lcd_panel_disp_sleep()` can reduce the power consumption of the LCD screen by entering the sleep mode. The internal frame buffer is still retained.

## LCD Data Panel Operations

- `esp_lcd_panel_reset()` can reset the LCD data panel.

- `esp_lcd_panel_init()` performs a basic initialization of the data panel.

- `esp_lcd_panel_draw_bitmap()` is the function which does the magic to flush the user draw buffer to the LCD screen, where the target draw window is configurable. Please note, this function expects the draw buffer is a 1-D array and there's no stride in between each lines.

## Steps to Add Manufacture Specific Initialization

The LCD controller drivers (e.g., st7789) in ESP-IDF only provide basic initialization in the `esp_lcd_panel_init()`, leaving the vast majority of settings to the default values. Some LCD modules needs to set a bunch of manufacture specific configurations before it can display normally. These configurations usually include gamma, power voltage and so on. If you want to add manufacture specific initialization, please follow the steps below:

    esp_lcd_panel_reset(panel_handle);
    esp_lcd_panel_init(panel_handle);
    // set extra configurations e.g., gamma control
    // with the underlying IO handle
    // please consult your manufacture for special commands and corresponding values
    esp_lcd_panel_io_tx_param(io_handle, GAMMA_CMD, (uint8_t[]) {
           GAMMA_ARRAY
        }, N);
    // turn on the display
    esp_lcd_panel_disp_on_off(panel_handle, true);

## Application Example

- Software JPEG decoding and display - peripherals/lcd/tjpgd

## API Reference

### Header File

- components/hal/include/hal/lcd_types.h

- This header file can be included with:

  >     #include "hal/lcd_types.h"

### Type Definitions

typedef int lcd_clock_source_t

### Enumerations

enum lcd_rgb_data_endian_t

  RGB data endian.

  Values:

  enumerator LCD_RGB_DATA_ENDIAN_BIG

    RGB data endian: MSB first

  enumerator LCD_RGB_DATA_ENDIAN_LITTLE

    RGB data endian: LSB first

enum lcd_color_space_t

  LCD color space.

  Values:

  enumerator LCD_COLOR_SPACE_RGB

    Color space: RGB

  enumerator LCD_COLOR_SPACE_YUV

    Color space: YUV

enum lcd_color_rgb_pixel_format_t

  LCD color pixel format in RGB color space.

  Values:

  enumerator LCD_COLOR_PIXEL_FORMAT_RGB565

    16 bits, 5 bits per R/B value, 6 bits for G value

  enumerator LCD_COLOR_PIXEL_FORMAT_RGB666

    18 bits, 6 bits per R/G/B value

  enumerator LCD_COLOR_PIXEL_FORMAT_RGB888

    24 bits, 8 bits per R/G/B value

enum lcd_color_format_t

  LCD color format.

  Values:

  enumerator LCD_COLOR_FMT_RGB565

    RGB565.

  enumerator LCD_COLOR_FMT_RGB666

    RGB666.

  enumerator LCD_COLOR_FMT_RGB888

    RGB888.

  enumerator LCD_COLOR_FMT_YUV422

    YUV422.

enum lcd_color_range_t

  LCD color range.

  Values:

  enumerator LCD_COLOR_RANGE_LIMIT

    Limited color range

  enumerator LCD_COLOR_RANGE_FULL

    Full color range

enum lcd_yuv_sample_t

  YUV sampling method.

  Values:

  enumerator LCD_YUV_SAMPLE_422

    YUV 4:2:2 sampling

  enumerator LCD_YUV_SAMPLE_420

    YUV 4:2:0 sampling

  enumerator LCD_YUV_SAMPLE_411

    YUV 4:1:1 sampling

enum lcd_yuv_conv_std_t

  The standard used for conversion between RGB and YUV.

  Values:

  enumerator LCD_YUV_CONV_STD_BT601

    YUV<->RGB conversion standard: BT.601

  enumerator LCD_YUV_CONV_STD_BT709

    YUV<->RGB conversion standard: BT.709

enum lcd_yuv422_pack_order_t

  YUV422 packing order.

  Values:

  enumerator LCD_YUV422_PACK_ORDER_YUYV

    YUYV

  enumerator LCD_YUV422_PACK_ORDER_YVYU

    YVYU

  enumerator LCD_YUV422_PACK_ORDER_UYVY

    UYVY

  enumerator LCD_YUV422_PACK_ORDER_VYUY

    VYUY

### Header File

- components/esp_lcd/include/esp_lcd_types.h

- This header file can be included with:

  >     #include "esp_lcd_types.h"

- This header file is a part of the API provided by the `esp_lcd` component. To declare that your component depends on `esp_lcd`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_lcd

  > or

  >     PRIV_REQUIRES esp_lcd

### Structures

struct esp_lcd_video_timing_t

  Timing parameters for the video data transmission.

  Public Members

  uint32_t h_size

    Horizontal resolution, i.e. the number of pixels in a line

  uint32_t v_size

    Vertical resolution, i.e. the number of lines in the frame

  uint32_t hsync_pulse_width

    Horizontal sync width, in pixel clock

  uint32_t hsync_back_porch

    Horizontal back porch, number of pixel clock between hsync and start of line active data

  uint32_t hsync_front_porch

    Horizontal front porch, number of pixel clock between the end of active data and the next hsync

  uint32_t vsync_pulse_width

    Vertical sync width, in number of lines

  uint32_t vsync_back_porch

    Vertical back porch, number of invalid lines between vsync and start of frame

  uint32_t vsync_front_porch

    Vertical front porch, number of invalid lines between the end of frame and the next vsync

struct esp_lcd_panel_io_event_data_t

  Type of LCD panel IO event data.

struct esp_lcd_panel_io_callbacks_t

  Type of LCD panel IO callbacks.

  Public Members

  esp_lcd_panel_io_color_trans_done_cb_t on_color_trans_done

    Callback invoked when color data transfer has finished

struct esp_lcd_color_conv_config_t

  Configuration of LCD color conversion.

  Public Members

  lcd_color_range_t in_color_range

    Color range of the input color

  lcd_color_range_t out_color_range

    Color range of the output color

  lcd_yuv_conv_std_t conv_std

    YUV conversion standard: BT601, BT709

  lcd_yuv422_pack_order_t in_pack_order

    YUV422 packing order of the input color

  struct esp_lcd_color_conv_config_t::[anonymous]::[anonymous]::[anonymous] yuv422

    YUV422 specific

  struct esp_lcd_color_conv_config_t::[anonymous]::[anonymous] yuv

    YUV specific

  union esp_lcd_color_conv_config_t::[anonymous] spec

    Extra configuration for specific color conversion

### Type Definitions

typedef struct esp_lcd_panel_io_t *esp_lcd_panel_io_handle_t

  Type of LCD panel IO handle

typedef struct esp_lcd_panel_t *esp_lcd_panel_handle_t

  Type of LCD panel handle

typedef bool (*esp_lcd_panel_io_color_trans_done_cb_t)(esp_lcd_panel_io_handle_t panel_io, esp_lcd_panel_io_event_data_t *edata, void *user_ctx)

  Declare the prototype of the function that will be invoked when panel IO finishes transferring color data.

  Param panel_io:

    [in] LCD panel IO handle, which is created by factory API like `esp_lcd_new_panel_io_spi()`

  Param edata:

    [in] Panel IO event data, fed by driver

  Param user_ctx:

    [in] User data, passed from `esp_lcd_panel_io_xxx_config_t`

  Return:

    Whether a high priority task has been waken up by this function

### Enumerations

enum lcd_rgb_element_order_t

  RGB element order.

  Values:

  enumerator LCD_RGB_ELEMENT_ORDER_RGB

    RGB element order: RGB

  enumerator LCD_RGB_ELEMENT_ORDER_BGR

    RGB element order: BGR

### Header File

- components/esp_lcd/include/esp_lcd_panel_io.h

- This header file can be included with:

  >     #include "esp_lcd_panel_io.h"

- This header file is a part of the API provided by the `esp_lcd` component. To declare that your component depends on `esp_lcd`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_lcd

  > or

  >     PRIV_REQUIRES esp_lcd

### Functions

esp_err_t esp_lcd_panel_io_rx_param(esp_lcd_panel_io_handle_t io, int lcd_cmd, void *param, size_t param_size)

  Transmit LCD command and receive corresponding parameters.

  备注

  Commands sent by this function are short, so they are sent using polling transactions. The function does not return before the command transfer is completed. If any queued transactions sent by `esp_lcd_panel_io_tx_color()` are still pending when this function is called, this function will wait until they are finished and the queue is empty before sending the command(s).

  参数:

    - io -- [in] LCD panel IO handle, which is created by other factory API like `esp_lcd_new_panel_io_spi()`

    - lcd_cmd -- [in] The specific LCD command, set to -1 if no command needed

    - param -- [out] Buffer for the command data

    - param_size -- [in] Size of `param` buffer

  返回:

    - ESP_ERR_INVALID_ARG if parameter is invalid

    - ESP_ERR_NOT_SUPPORTED if read is not supported by transport

    - ESP_OK on success

esp_err_t esp_lcd_panel_io_tx_param(esp_lcd_panel_io_handle_t io, int lcd_cmd, const void *param, size_t param_size)

  Transmit LCD command and corresponding parameters.

  备注

  Commands sent by this function are short, so they are sent using polling transactions. The function does not return before the command transfer is completed. If any queued transactions sent by `esp_lcd_panel_io_tx_color()` are still pending when this function is called, this function will wait until they are finished and the queue is empty before sending the command(s).

  参数:

    - io -- [in] LCD panel IO handle, which is created by other factory API like `esp_lcd_new_panel_io_spi()`

    - lcd_cmd -- [in] The specific LCD command, set to -1 if no command needed

    - param -- [in] Buffer that holds the command specific parameters, set to NULL if no parameter is needed for the command

    - param_size -- [in] Size of `param` in memory, in bytes, set to zero if no parameter is needed for the command

  返回:

    - ESP_ERR_INVALID_ARG if parameter is invalid

    - ESP_OK on success

esp_err_t esp_lcd_panel_io_tx_color(esp_lcd_panel_io_handle_t io, int lcd_cmd, const void *color, size_t color_size)

  Transmit LCD RGB data.

  备注

  This function will package the command and RGB data into a transaction, and push into a queue. The real transmission is performed in the background (DMA+interrupt). The caller should take care of the lifecycle of the `color` buffer. Recycling of color buffer should be done in the callback `on_color_trans_done()`.

  参数:

    - io -- [in] LCD panel IO handle, which is created by factory API like `esp_lcd_new_panel_io_spi()`

    - lcd_cmd -- [in] The specific LCD command, set to -1 if no command needed

    - color -- [in] Buffer that holds the RGB color data

    - color_size -- [in] Size of `color` in memory, in bytes

  返回:

    - ESP_ERR_INVALID_ARG if parameter is invalid

    - ESP_OK on success

esp_err_t esp_lcd_panel_io_del(esp_lcd_panel_io_handle_t io)

  Destroy LCD panel IO handle (deinitialize panel and free all corresponding resource)

  参数:

    io -- [in] LCD panel IO handle, which is created by factory API like `esp_lcd_new_panel_io_spi()`

  返回:

    - ESP_ERR_INVALID_ARG if parameter is invalid

    - ESP_OK on success

esp_err_t esp_lcd_panel_io_register_event_callbacks(esp_lcd_panel_io_handle_t io, const esp_lcd_panel_io_callbacks_t *cbs, void *user_ctx)

  Register LCD panel IO callbacks.

  参数:

    - io -- [in] LCD panel IO handle, which is created by factory API like `esp_lcd_new_panel_io_spi()`

    - cbs -- [in] structure with all LCD panel IO callbacks

    - user_ctx -- [in] User private data, passed directly to callback's user_ctx

  返回:

    - ESP_ERR_INVALID_ARG if parameter is invalid

    - ESP_OK on success

### Header File

- components/esp_lcd/include/esp_lcd_panel_ops.h

- This header file can be included with:

  >     #include "esp_lcd_panel_ops.h"

- This header file is a part of the API provided by the `esp_lcd` component. To declare that your component depends on `esp_lcd`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_lcd

  > or

  >     PRIV_REQUIRES esp_lcd

### Functions

esp_err_t esp_lcd_panel_reset(esp_lcd_panel_handle_t panel)

  Reset LCD panel.

  备注

  Panel reset must be called before attempting to initialize the panel using `esp_lcd_panel_init()`.

  参数:

    panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

  返回:

    - ESP_OK on success

esp_err_t esp_lcd_panel_init(esp_lcd_panel_handle_t panel)

  Initialize LCD panel.

  备注

  Before calling this function, make sure the LCD panel has finished the `reset` stage by `esp_lcd_panel_reset()`.

  参数:

    panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

  返回:

    - ESP_OK on success

esp_err_t esp_lcd_panel_del(esp_lcd_panel_handle_t panel)

  Deinitialize the LCD panel.

  参数:

    panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

  返回:

    - ESP_OK on success

esp_err_t esp_lcd_panel_draw_bitmap(esp_lcd_panel_handle_t panel, int x_start, int y_start, int x_end, int y_end, const void *color_data)

  Draw bitmap on LCD panel.

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - x_start -- [in] Start pixel index in the target frame buffer, on x-axis (x_start is included)

    - y_start -- [in] Start pixel index in the target frame buffer, on y-axis (y_start is included)

    - x_end -- [in] End pixel index in the target frame buffer, on x-axis (x_end is not included)

    - y_end -- [in] End pixel index in the target frame buffer, on y-axis (y_end is not included)

    - color_data -- [in] RGB color data that will be dumped to the specific window range

  返回:

    - ESP_OK on success

esp_err_t esp_lcd_panel_mirror(esp_lcd_panel_handle_t panel, bool mirror_x, bool mirror_y)

  Mirror the LCD panel on specific axis.

  备注

  Combined with `esp_lcd_panel_swap_xy()`, one can realize screen rotation

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - mirror_x -- [in] Whether the panel will be mirrored about the x axis

    - mirror_y -- [in] Whether the panel will be mirrored about the y axis

  返回:

    - ESP_OK on success

    - ESP_ERR_NOT_SUPPORTED if this function is not supported by the panel

esp_err_t esp_lcd_panel_swap_xy(esp_lcd_panel_handle_t panel, bool swap_axes)

  Swap/Exchange x and y axis.

  备注

  Combined with `esp_lcd_panel_mirror()`, one can realize screen rotation

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - swap_axes -- [in] Whether to swap the x and y axis

  返回:

    - ESP_OK on success

    - ESP_ERR_NOT_SUPPORTED if this function is not supported by the panel

esp_err_t esp_lcd_panel_set_gap(esp_lcd_panel_handle_t panel, int x_gap, int y_gap)

  Set extra gap in x and y axis.

  The gap is the space (in pixels) between the left/top sides of the LCD panel and the first row/column respectively of the actual contents displayed.

  备注

  Setting a gap is useful when positioning or centering a frame that is smaller than the LCD.

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - x_gap -- [in] Extra gap on x axis, in pixels

    - y_gap -- [in] Extra gap on y axis, in pixels

  返回:

    - ESP_OK on success

esp_err_t esp_lcd_panel_invert_color(esp_lcd_panel_handle_t panel, bool invert_color_data)

  Invert the color (bit-wise invert the color data line)

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - invert_color_data -- [in] Whether to invert the color data

  返回:

    - ESP_OK on success

esp_err_t esp_lcd_panel_disp_on_off(esp_lcd_panel_handle_t panel, bool on_off)

  Turn on or off the display.

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - on_off -- [in] True to turns on display, False to turns off display

  返回:

    - ESP_OK on success

    - ESP_ERR_NOT_SUPPORTED if this function is not supported by the panel

esp_err_t esp_lcd_panel_disp_off(esp_lcd_panel_handle_t panel, bool off)

  Turn off the display.

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - off -- [in] Whether to turn off the screen

  返回:

    - ESP_OK on success

    - ESP_ERR_NOT_SUPPORTED if this function is not supported by the panel

esp_err_t esp_lcd_panel_disp_sleep(esp_lcd_panel_handle_t panel, bool sleep)

  Enter or exit sleep mode.

  参数:

    - panel -- [in] LCD panel handle, which is created by other factory API like `esp_lcd_new_panel_st7789()`

    - sleep -- [in] True to enter sleep mode, False to wake up

  返回:

    - ESP_OK on success

    - ESP_ERR_NOT_SUPPORTED if this function is not supported by the panel

### Header File

- components/esp_lcd/include/esp_lcd_panel_vendor.h

- This header file can be included with:

  >     #include "esp_lcd_panel_vendor.h"

- This header file is a part of the API provided by the `esp_lcd` component. To declare that your component depends on `esp_lcd`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_lcd

  > or

  >     PRIV_REQUIRES esp_lcd

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