# SPI Interfaced LCD

[中文]

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_spi_config_t::dc_gpio_num` sets the GPIO number for the DC signal line (some LCD calls this `RS` line). The LCD driver uses this GPIO to switch between sending command and sending data.

   > - `esp_lcd_panel_io_spi_config_t::cs_gpio_num` sets the GPIO number for the CS signal line. The LCD driver uses this GPIO to select the LCD chip. If the SPI bus only has one device attached (i.e., this LCD), you can set the GPIO number to `-1` to occupy the bus exclusively.

   > - `esp_lcd_panel_io_spi_config_t::pclk_hz` sets the frequency of the pixel clock, in Hz. The value should not exceed the range recommended in the LCD spec.

   > - `esp_lcd_panel_io_spi_config_t::spi_mode` sets the SPI mode. The LCD driver uses this mode to communicate with the LCD. For the meaning of the SPI mode, please refer to the SPI Master API doc.

   > - `esp_lcd_panel_io_spi_config_t::lcd_cmd_bits` and `esp_lcd_panel_io_spi_config_t::lcd_param_bits` set the bit width of the command and parameter that recognized by the LCD controller chip. This is chip specific, you should refer to your LCD spec in advance.

   > - `esp_lcd_panel_io_spi_config_t::trans_queue_depth` sets the depth of the SPI transaction queue. A bigger value means more transactions can be queued up, but it also consumes more memory.

   > - `esp_lcd_panel_io_spi_config_t::cs_ena_pretrans` sets the amount of SPI bit-cycles which the cs should be activated before the transmission (0-16).

   > - `esp_lcd_panel_io_spi_config_t::cs_ena_posttrans` sets the amount of SPI bit-cycles which the cs should stay active after the transmission (0-16).

   >     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

  gpio_num_t cs_gpio_num

    GPIO used for CS line

  gpio_num_t 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)

  struct esp_lcd_panel_io_spi_config_t::esp_lcd_spi_flags_t flags

    Extra flags to fine-tune the SPI device

  struct esp_lcd_spi_flags_t

    Extra flags to fine-tune the SPI device.

    Public Members

    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 data and parameters with 8 lines

    unsigned int quad_mode

      transmit data and parameters with 4 lines

    unsigned int sio_mode

      Read and write through a single data line (MOSI)

    unsigned int psram_dma_direct

      If color buffer is in PSRAM, use PSRAM for DMA buffer directly, has speed limit, but no temp buffer and save memory

    unsigned int lsb_first

      Transmit LSB bit first

    unsigned int cs_high_active

      CS line is high active

### Type Definitions

typedef int esp_lcd_spi_bus_handle_t

  Type of LCD SPI bus handle

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