[lvgl][l475] use single buffer instead of double buffers

Author: mysterywolf

bsp/stm32/stm32l475-atk-pandora/applications/lvgl/lv_port_disp.c

@@ -10,8 +10,8 @@
 #include <lvgl.h>
 #include <drv_lcd.h>
 
-#define MY_DISP_HOR_RES LCD_W
-#define DISP_BUFFER_LINES 70
+#define MY_DISP_HOR_RES     LCD_W
+#define DISP_BUFFER_LINES   (LCD_H/5)
 
 /*A static or global variable to store the buffers*/
 static lv_disp_draw_buf_t disp_buf;
@@ -21,7 +21,6 @@ static lv_disp_drv_t disp_drv;
 
 /*Static or global buffer(s). The second buffer is optional*/
 static lv_color_t buf_1[MY_DISP_HOR_RES * DISP_BUFFER_LINES];
-static lv_color_t buf_2[MY_DISP_HOR_RES * DISP_BUFFER_LINES];
 
 /*Flush the content of the internal buffer the specific area on the display
  *You can use DMA or any hardware acceleration to do this operation in the background but
@@ -39,7 +38,7 @@ static void disp_flush(lv_disp_drv_t * disp_drv, const lv_area_t * area, lv_colo
 void lv_port_disp_init(void)
 {
     /*Initialize `disp_buf` with the buffer(s). With only one buffer use NULL instead buf_2 */
-    lv_disp_draw_buf_init(&disp_buf, buf_1, buf_2, MY_DISP_HOR_RES * DISP_BUFFER_LINES);
+    lv_disp_draw_buf_init(&disp_buf, buf_1, RT_NULL, MY_DISP_HOR_RES * DISP_BUFFER_LINES);
 
     lv_disp_drv_init(&disp_drv); /*Basic initialization*/