text: /**
   * @file disp_spi.c
   *
   */
  
  /*********************
   *      INCLUDES
   *********************/
  #include "disp_spi.h"
  #include "esp_system.h"
  #include "driver/gpio.h"
  #include "driver/spi_master.h"
  #include <string.h>
  #include <freertos/FreeRTOS.h>
  #include <freertos/semphr.h>
  #include "freertos/task.h"
  #include "lvgl/lvgl.h"
  #include "st7789.h"
  #include "sdkconfig.h"
  
  /*********************
   *      DEFINES
   *********************/
  
  /**********************
   *      TYPEDEFS
   **********************/
  
  /**********************
   *  STATIC PROTOTYPES
   **********************/
  static void IRAM_ATTR spi_ready (spi_transaction_t *trans);
  
  /**********************
   *  STATIC VARIABLES
   **********************/
  static spi_device_handle_t spi;
  static volatile bool spi_trans_in_progress;
  static volatile bool spi_color_sent;
  
  /**********************
   *      MACROS
   **********************/
  
  /**********************
   *   GLOBAL FUNCTIONS
   **********************/
  void disp_spi_init(void)
  {
  
      esp_err_t ret;
  
      spi_bus_config_t buscfg={
              .miso_io_num=-1,
              .mosi_io_num=DISP_SPI_MOSI,
              .sclk_io_num=DISP_SPI_CLK,
              .quadwp_io_num=-1,
              .quadhd_io_num=-1,
              .max_transfer_sz = DISP_BUF_SIZE * 2, // defined currently in st7789 - which is silly!
      };
  
      spi_device_interface_config_t devcfg={
              .clock_speed_hz=CONFIG_DISP_SPI_SPEED*1000*1000,           //Clock out at 40 MHz
              .mode=0,                                //SPI mode 0
              .spics_io_num=DISP_SPI_CS,              //CS pin
              .queue_size=1,
              .pre_cb=NULL,
              .post_cb=spi_ready,
              .flags = SPI_DEVICE_HALFDUPLEX
      };
  
      //Initialize the SPI bus
      ret=spi_bus_initialize(HSPI_HOST, &buscfg, 1);
      assert(ret==ESP_OK);
  
      //Attach the LCD to the SPI bus
      ret=spi_bus_add_device(HSPI_HOST, &devcfg, &spi);
      assert(ret==ESP_OK);
  }
  
  void disp_spi_send_data(uint8_t * data, uint16_t length)
  {
      if (length == 0) return;           //no need to send anything
  
      while(spi_trans_in_progress);
  
      spi_transaction_t t = {
          .length = length * 8, // transaction length is in bits
          .tx_buffer = data
      };
  
      spi_trans_in_progress = true;
      spi_color_sent = false;             //Mark the "lv_flush_ready" NOT needs to be called in "spi_ready"
      spi_device_queue_trans(spi, &t, portMAX_DELAY);
  
  }
  
  void disp_spi_send_colors(uint8_t * data, uint16_t length)
  {
      if (length == 0) return;           //no need to send anything
  
      while(spi_trans_in_progress);
  
      spi_transaction_t t = {
          .length = length * 8, // transaction length is in bits
          .tx_buffer = data
      };
      
      spi_trans_in_progress = true;
      spi_color_sent = true;              //Mark the "lv_flush_ready" needs to be called in "spi_ready"
      spi_device_queue_trans(spi, &t, portMAX_DELAY);
  }
  
  
  /**********************
   *   STATIC FUNCTIONS
   **********************/
  
  static void IRAM_ATTR spi_ready (spi_transaction_t *trans)
  {
      spi_trans_in_progress = false;
  
      lv_disp_t * disp = lv_refr_get_disp_refreshing();
      if(spi_color_sent) lv_disp_flush_ready(&disp->driver);
  }
  