/* : this draws a vertical line on the frame buffer  */
void iot_epaper_draw_vertical_line(epaper_handle_t dev, int x, int y, int height, int colored)
/* : this draws a vertical line on the frame buffer  */
void iot_epaper_draw_vertical_line(epaper_handle_t dev, int x, int y, int height, int colored)
{
    int i;
    epaper_dev_t* device = (epaper_dev_t*) dev;
    xSemaphoreTakeRecursive(device->spi_mux, portMAX_DELAY);
    for (i = y; i < y + height; i++) {
        iot_epaper_draw_pixel(dev, x, i, colored);
    }
    xSemaphoreGiveRecursive(device->spi_mux);
}