app is invalid if both of its 2 first words are empty mask

Author: hathach

lib/sdk11/components/libraries/bootloader_dfu/bootloader.c

@@ -138,12 +138,20 @@ static void wait_for_events(void)
 
 bool bootloader_app_is_valid(void)
 {
+  bool success = false;
   uint32_t const app_addr = DFU_BANK_0_REGION_START;
+
   bootloader_settings_t const *p_bootloader_settings;
+  bootloader_util_settings_get(&p_bootloader_settings);
 
-  bool success = false;
+  enum { EMPTY_FLASH = 0xFFFFFFFFUL };
 
-  bootloader_util_settings_get(&p_bootloader_settings);
+  // Application is invalid if first 2 words are all 0xFFFFFFF
+  if ( *((uint32_t *)app_addr    ) == EMPTY_FLASH &&
+       *((uint32_t *)(app_addr+4)) == EMPTY_FLASH )
+  {
+    return false;
+  }
 
   // The application in CODE region 1 is flagged as valid during update.
   if ( p_bootloader_settings->bank_0 == BANK_VALID_APP )