Fix/esp32s2 memory allocation

README.md

@@ -119,7 +119,16 @@ For more information see: [platformio with espidf framework compability](https:/
 
 # ESP32-S2 Support
 
-Support for ESP32-S2 variant isn't tested, the current drivers implementation
-would needs to be improved because this target available memory is less than
-ESP32 targets. The menuconfig interface also would need to be improved to take
-this into account.
+Support for ESP32-S2 variant is Work In Progress.
+Smaller displays (e.g. 320x240) work fine, but larger ones need testing.
+
+## Background
+
+ESP32-S2 has less on-chip SRAM than its predecessor ESP32 (520kB vs. 320kB).
+This causes problems with memory allocation with large LVGL display buffers as they don't fit into the on-chip memory
+and external PSRAM is not accessible by DMA.
+
+Moreover, static allocation to external PSRAM is not yet supported
+(see [GitHub issue](https://github.com/espressif/esp-idf/issues/6162)).
+
+At this momement, the buffers are dynamicaly allocated with DMA capabilty and memory allocator handles the rest.

main/main.c

@@ -1,5 +1,5 @@
 /* LVGL Example project
- * 
+ *
  * Basic project to test LVGL on ESP32 based projects.
  *
  * This example code is in the Public Domain (or CC0 licensed, at your option.)
@@ -60,7 +60,7 @@ static void create_demo_application(void);
  *   APPLICATION MAIN
  **********************/
 void app_main() {
-    
+
     /* If you want to use a task to create the graphic, you NEED to create a Pinned task
      * Otherwise there can be problem such as memory corruption and so on.
      * NOTE: When not using Wi-Fi nor Bluetooth you can pin the guiTask to core 0 */
@@ -73,20 +73,22 @@ void app_main() {
 SemaphoreHandle_t xGuiSemaphore;
 
 static void guiTask(void *pvParameter) {
-    
+
     (void) pvParameter;
     xGuiSemaphore = xSemaphoreCreateMutex();
 
     lv_init();
-    
+
     /* Initialize SPI or I2C bus used by the drivers */
     lvgl_driver_init();
 
-    static lv_color_t buf1[DISP_BUF_SIZE];
+    lv_color_t* buf1 = heap_caps_malloc(DISP_BUF_SIZE * sizeof(lv_color_t), MALLOC_CAP_DMA);
+    assert(buf1 != NULL);
 
     /* Use double buffered when not working with monochrome displays */
 #ifndef CONFIG_LV_TFT_DISPLAY_MONOCHROME
-    static lv_color_t buf2[DISP_BUF_SIZE];
+    lv_color_t* buf2 = heap_caps_malloc(DISP_BUF_SIZE * sizeof(lv_color_t), MALLOC_CAP_DMA);
+    assert(buf2 != NULL);
 #else
     static lv_color_t *buf2 = NULL;
 #endif
@@ -98,7 +100,7 @@ static void guiTask(void *pvParameter) {
 #if defined CONFIG_LV_TFT_DISPLAY_CONTROLLER_IL3820 \
     || defined CONFIG_LV_TFT_DISPLAY_CONTROLLER_JD79653A \
     || defined CONFIG_LV_TFT_DISPLAY_CONTROLLER_UC8151D
-    
+
     /* Actual size in pixels, not bytes. */
     size_in_px *= 8;
 #endif
@@ -130,7 +132,7 @@ static void guiTask(void *pvParameter) {
     indev_drv.type = LV_INDEV_TYPE_POINTER;
     lv_indev_drv_register(&indev_drv);
 #endif
-    
+
     /* Create and start a periodic timer interrupt to call lv_tick_inc */
     const esp_timer_create_args_t periodic_timer_args = {
         .callback = &lv_tick_task,
@@ -142,7 +144,7 @@ static void guiTask(void *pvParameter) {
 
     /* Create the demo application */
     create_demo_application();
-    
+
     while (1) {
         /* Delay 1 tick (assumes FreeRTOS tick is 10ms */
         vTaskDelay(pdMS_TO_TICKS(10));
@@ -155,16 +157,20 @@ static void guiTask(void *pvParameter) {
     }
 
     /* A task should NEVER return */
+    free(buf1);
+#ifndef CONFIG_LV_TFT_DISPLAY_MONOCHROME
+    free(buf2);
+#endif
     vTaskDelete(NULL);
 }
 
 static void create_demo_application(void)
 {
-    /* When using a monochrome display we only show "Hello World" centered on the 
+    /* When using a monochrome display we only show "Hello World" centered on the
      * screen */
 #if defined CONFIG_LV_TFT_DISPLAY_MONOCHROME || \
     defined CONFIG_LV_TFT_DISPLAY_CONTROLLER_ST7735S
-    
+
     /* use a pretty small demo for monochrome displays */
     /* Get the current screen  */
     lv_obj_t * scr = lv_disp_get_scr_act(NULL);