Firmware & Software

/*!
* @brief Sends image from SD card to LCD 
* @param[in] x_in Initial X position
* @param[in] y_in Initial Y position
* @param[in] x_fin Final X position
* @param[in] y_fin Final Y position
* @param[in] memory_starting_address Memory block location of the image on the SD card
* @return NONE
*
* NOTE: This function appears long and unruly due to the fact that many intermediate
*       functions were unrolled and optimization for speed was performed
*/
void
lcd_image_from_sd(uint16_t x_in ,uint16_t y_in,uint16_t x_fin ,uint16_t y_fin, uint32_t memory_starting_address)
{
   uint32_t total_blocks = 0, total_bytes = 0;
   
   //Formula: total-bytes = ((total-pixels) x (3 bytes-per-pixel))
   total_bytes = ((x_fin - x_in) * (y_fin - y_in) * 3);
   
   //512 bytes-per-block
   total_blocks = (total_bytes / 512);

   //Select LCD
   gpio_clear(LCD_CS);
   
   //Set upper left corner of image as starting address
   lcd_set_window_address(x_in, y_in, x_fin - 1, y_fin - 1);

   //Put LCD in data mode
   gpio_set(LCD_RS); //LCD_RS=1;
   
   //Start reading the image from the SD card
   sd_read_multiple_block(memory_starting_address);
   
   //Burn through the header to get to the image, starts at 0x36 offset 
   uint32_t current_byte = 512;
   current_byte -= lcd_skip_bmp_header();

   uint32_t color_buffer[6] = {0}; // blue green red blue green red
   uint32_t color_number = 0;
   
   for(uint32_t block_number = total_blocks; block_number != 0; --block_number)
   {

      while(0 != current_byte)
      {
         /* This is just spi_receive_byte(0xFF) unrolled */
         //Send dummy byte byte
         SPI2->DR = 0xFF;

         // Wait for the receive register to fill
         while(!(SPI2->SR & SPI_SR_RXNE)){}

         color_buffer[color_number] = (SPI2->DR);
         color_number++;
         
         if(6 == color_number)
         {
            //First Pixel
            GPIOB->BSRR = 0xFFFF0000; //Clear data bus
            GPIOB->BSRR = ((color_buffer[2] & 0xF8) | (color_buffer[1] >> 5)); //byte_high;
            GPIOA->BSRR = 0x00000100;//Set LCD_WR
            GPIOA->BSRR = 0x01000000; //Clear LCD_WR

            GPIOB->BSRR = 0xFFFF0000; //Clear data bus
            GPIOB->BSRR = (((color_buffer[1] & 0x1C) << 3) | (color_buffer[0] >> 3)); //byte_low;
            GPIOA->BSRR = 0x00000100;//Set LCD_WR
            GPIOA->BSRR = 0x01000000; //Clear LCD_WR

            //Second Pixel
            GPIOB->BSRR = 0xFFFF0000; //Clear data bus
            GPIOB->BSRR = ((color_buffer[5] & 0xF8) | (color_buffer[4] >> 5)); //byte_high;
            GPIOA->BSRR = 0x00000100;//Set LCD_WR
            GPIOA->BSRR = 0x01000000; ////Clear LCD_WR

            GPIOB->BSRR = 0xFFFF0000; //Clear data bus
            GPIOB->BSRR = (((color_buffer[4] & 0x1C) << 3) | (color_buffer[3] >> 3)); //byte_low;
            GPIOA->BSRR = 0x00000100;//Set LCD_WR
            GPIOA->BSRR = 0x01000000; ////Clear LCD_WR

            color_number = 0;
         }
         
         current_byte--;

      }

      current_byte = 512;
       
      //Burn through the CRC bits and wait until SD card sends data valid token
      spi_receive_byte(0xFF);
      spi_receive_byte(0xFF);
      while(SD_CMD17_TOKEN != spi_receive_byte(0xFF)) {} //CMD17 token is the same as CMD18, 0xFE
   }
   
   //The sd card must return an entire block. Flush the unused bytes from the last block
   sd_stop_transmission();
}