Read-GRAM

#define LINE_SIZE 320

struct mgos_col_rgb *mgos_ili9341_read_line_rgb(int16_t w, int16_t y) {
  static struct mgos_col_rgb pixBuf[LINE_SIZE];
  uint8_t pixChar;
  size_t bufSize = LINE_SIZE * sizeof(struct mgos_col_rgb);
  int x0, x1, y0, y1;

  x0 = 0;
  x1 = w - 1;
  y0 = y;
  y1 = y + 1;

  mgos_ili9341_spi_write8_cmd(ILI9341_CASET); // Column addr set
  mgos_ili9341_spi_write8(x0 >> 8);
  mgos_ili9341_spi_write8(x0 & 0xFF);         // XSTART
  mgos_ili9341_spi_write8(x1 >> 8);
  mgos_ili9341_spi_write8(x1 & 0xFF);         // XEND
  mgos_ili9341_spi_write8_cmd(ILI9341_PASET); // Row addr set
  mgos_ili9341_spi_write8(y0 >> 8);
  mgos_ili9341_spi_write8(y0 & 0xFF);         // YSTART
  mgos_ili9341_spi_write8(y1 >> 8);
  mgos_ili9341_spi_write8(y1 & 0xFF);         // YEND
  mgos_ili9341_spi_write8_cmd(ILI9341_RAMRD); // read from RAM

  mgos_gpio_write(mgos_sys_config_get_ili9341_dc_pin(), 1);

   //mgos_ili9341_spi_read(&pixChar, 1); //dummy read
  memset(pixBuf, 0xFF, LINE_SIZE * sizeof(struct mgos_col_rgb));

  struct mgos_spi *spi = mgos_spi_get_global();
  if (!spi) {
    LOG(LL_ERROR, ("SPI is disabled, set spi.enable=true"));
    return false;
  }

  struct mgos_spi_txn txn = {
    .cs   = mgos_sys_config_get_ili9341_cs_index(),
    .mode = SPI_MODE,
    .freq = mgos_sys_config_get_ili9341_spi_freq(),
    .hd.tx_data   = NULL,
    .hd.tx_len    = 0,
    .hd.dummy_len = 1,
    .hd.rx_len    = bufSize,
    .hd.rx_data   = (uint8_t *) pixBuf
  };

  if (mgos_spi_run_txn(spi, false, &txn)) {
    LOG(LL_INFO, ("SPI data received, size: <%d>", txn.hd.rx_len));
    return pixBuf;
  } else {
    LOG(LL_INFO, ("Error, no SPI data received!"));
    return NULL;
  }
}