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SPI Interfaced LCD

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  1. Create an SPI bus. Please refer to SPI Master API doc for more details.

    Currently the driver supports SPI, Quad SPI and Octal SPI (simulate Intel 8080 timing) modes.

    spi_bus_config_t buscfg = {
    .sclk_io_num = EXAMPLE_PIN_NUM_SCLK,
    .mosi_io_num = EXAMPLE_PIN_NUM_MOSI,
    .miso_io_num = EXAMPLE_PIN_NUM_MISO,
    .quadwp_io_num = -1,
    .quadhd_io_num = -1,
    .max_transfer_sz = EXAMPLE_LCD_H_RES * 80 * sizeof(uint16_t), // transfer 80 lines of pixels (assume pixel is RGB565) at most in one SPI transaction
};
ESP_ERROR_CHECK(spi_bus_initialize(LCD_HOST, &buscfg, SPI_DMA_CH_AUTO)); // Enable the DMA feature

  2. Allocate an LCD IO device handle from the SPI bus. In this step, you need to provide the following information:

    esp_lcd_panel_io_handle_t io_handle = NULL;
esp_lcd_panel_io_spi_config_t io_config = {
    .dc_gpio_num = EXAMPLE_PIN_NUM_LCD_DC,
    .cs_gpio_num = EXAMPLE_PIN_NUM_LCD_CS,
    .pclk_hz = EXAMPLE_LCD_PIXEL_CLOCK_HZ,
    .lcd_cmd_bits = EXAMPLE_LCD_CMD_BITS,
    .lcd_param_bits = EXAMPLE_LCD_PARAM_BITS,
    .spi_mode = 0,
    .trans_queue_depth = 10,
};
// Attach the LCD to the SPI bus
ESP_ERROR_CHECK(esp_lcd_new_panel_io_spi((esp_lcd_spi_bus_handle_t)LCD_HOST, &io_config, &io_handle));

  3. Install the LCD controller driver. The LCD controller driver is responsible for sending the commands and parameters to the LCD controller chip. In this step, you need to specify the SPI IO device handle that allocated in the last step, and some panel specific configurations:

    • esp_lcd_panel_dev_config_t::reset_gpio_num sets the LCD's hardware reset GPIO number. If the LCD does not have a hardware reset pin, set this to -1.

    • esp_lcd_panel_dev_config_t::rgb_ele_order sets the RGB element order of each color data.

    • esp_lcd_panel_dev_config_t::bits_per_pixel sets the bit width of the pixel color data. The LCD driver uses this value to calculate the number of bytes to send to the LCD controller chip.

    • esp_lcd_panel_dev_config_t::data_endian specifies the data endian to be transmitted to the screen. No need to specify for color data within one byte, like RGB232. For drivers that do not support specifying data endian, this field would be ignored.

    esp_lcd_panel_handle_t panel_handle = NULL;
esp_lcd_panel_dev_config_t panel_config = {
    .reset_gpio_num = EXAMPLE_PIN_NUM_RST,
    .rgb_ele_order = LCD_RGB_ELEMENT_ORDER_BGR,
    .bits_per_pixel = 16,
};
// Create LCD panel handle for ST7789, with the SPI IO device handle
ESP_ERROR_CHECK(esp_lcd_new_panel_st7789(io_handle, &panel_config, &panel_handle));

API Reference

Header File

  • components/esp_lcd/include/esp_lcd_io_spi.h

  • This header file can be included with:

    #include "esp_lcd_io_spi.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_new_panel_io_spi(esp_lcd_spi_bus_handle_t bus, const esp_lcd_panel_io_spi_config_t *io_config, esp_lcd_panel_io_handle_t *ret_io)

Create LCD panel IO handle, for SPI interface.

Parameters

  • bus -- [in] SPI bus handle

  • io_config -- [in] IO configuration, for SPI interface

  • ret_io -- [out] Returned IO handle

Returns

  • ESP_ERR_INVALID_ARG if parameter is invalid

  • ESP_ERR_NO_MEM if out of memory

  • ESP_OK on success

Structures

struct esp_lcd_panel_io_spi_config_t

Panel IO configuration structure, for SPI interface.

Public Members

int cs_gpio_num

GPIO used for CS line

int dc_gpio_num

GPIO used to select the D/C line, set this to -1 if the D/C line is not used

int spi_mode

Traditional SPI mode (0~3)

unsigned int pclk_hz

Frequency of pixel clock

size_t trans_queue_depth

Size of internal transaction queue

esp_lcd_panel_io_color_trans_done_cb_t on_color_trans_done

Callback invoked when color data transfer has finished

void *user_ctx

User private data, passed directly to on_color_trans_done's user_ctx

int lcd_cmd_bits

Bit-width of LCD command

int lcd_param_bits

Bit-width of LCD parameter

uint8_t cs_ena_pretrans

Amount of SPI bit-cycles the cs should be activated before the transmission (0-16)

uint8_t cs_ena_posttrans

Amount of SPI bit-cycles the cs should stay active after the transmission (0-16)

unsigned int dc_high_on_cmd

If enabled, DC level = 1 indicates command transfer

unsigned int dc_low_on_data

If enabled, DC level = 0 indicates color data transfer

unsigned int dc_low_on_param

If enabled, DC level = 0 indicates parameter transfer

unsigned int octal_mode

transmit with octal mode (8 data lines), this mode is used to simulate Intel 8080 timing

unsigned int quad_mode

transmit with quad mode (4 data lines), this mode is useful when transmitting LCD parameters (Only use one line for command)

unsigned int sio_mode

Read and write through a single data line (MOSI)

unsigned int lsb_first

transmit LSB bit first

unsigned int cs_high_active

CS line is high active

struct esp_lcd_panel_io_spi_config_t::[anonymous] flags

Extra flags to fine-tune the SPI device

Type Definitions

typedef int esp_lcd_spi_bus_handle_t

Type of LCD SPI bus handle

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