LCD

[English]

简介

ESP 系列芯片可以发出市场上常见的 LCD(如 SPI LCD、I2C LCD、并行 LCD (Intel 8080)、RGB/SRGB LCD、MIPI DSI LCD 等)所需的各种时序。esp_lcd 组件为上述各类 LCD 提供了一个统一的抽象驱动框架。

LCD 通常由两个主要平面组成:

  • 控制平面:通过该平面,可以读取、写入 LCD 设备控制器的内部寄存器。主机通常使用该平面来初始化 LCD 电源或进行伽玛校正等。

  • 数据平面:数据平面负责向 LCD 设备传输像素数据。

功能概述

esp_lcd 的上下文中,数据平面和控制平面都由 esp_lcd_panel_handle_t 数据类型表示。

在某些 LCD 中,上述两个平面可能会合并为一个平面。此时,像素数据通过控制平面传输,实现类似数据平面的功能。这在 SPI LCD 和 I2C LCD 中很常见。

此外,还有一些 LCD 不需要单独的控制平面。例如,某些 RGB LCD 在上电后会自动执行必要的初始化过程,主机只需通过数据平面不断刷新像素数据即可。但要注意,并非所有 RGB LCD 都完全不需要控制平面。部分 LCD 设备同时支持多种接口,需要主机通过控制平面(例如基于 SPI 接口)发送特定命令以启用 RGB 模式。

本文将讨论如何为不同类型的 LCD 创建控制平面和数据平面。

备注

ESP-IDF 仓库中自带的 LCD 设备控制器驱动程序数量有限(例如,ST7789 驱动程序是开箱即用的)。更多驱动程序可通过 乐鑫组件注册表 获取。

LCD 控制面板操作

LCD 数据面板操作

  • esp_lcd_panel_reset() 可以重置 LCD 数据面板。

  • esp_lcd_panel_init() 执行基本的数据面板初始化。

  • esp_lcd_panel_draw_bitmap() 可以将绘制 buffer 刷新到 LCD 屏幕上,其中目标绘制窗口是可配置的。请注意,使用该函数需要确保绘制 buffer 是一维数组,且每行像素数据之间没有跨距。

添加特定制造商的初始化设置

在 ESP-IDF 中,LCD 控制器驱动程序(例如 st7789)在函数 esp_lcd_panel_init() 中只提供了基本的控制面板初始化设置,大部分设置使用默认值。部分 LCD 模组需要进行一系列特定制造商的配置(通常包含伽玛配置、电压配置等)才能正常显示。若想添加特定制造商的初始化设置,请参照以下步骤:

esp_lcd_panel_reset(panel_handle);
esp_lcd_panel_init(panel_handle);
// 进行额外的配置,例如伽玛控制
// 使用底层 IO 句柄
// 请咨询制造商来获取特殊命令和相应的值
esp_lcd_panel_io_tx_param(io_handle, GAMMA_CMD, (uint8_t[]) {
       GAMMA_ARRAY
    }, N);
// 打开显示屏
esp_lcd_panel_disp_on_off(panel_handle, true);

应用示例

API 参考

Header File

Type Definitions

typedef soc_periph_lcd_clk_src_t lcd_clock_source_t

LCD clock source.

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_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

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

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