diff --git a/demos/os/rtthread/stm32f4xx/app/src/app_bak.c b/demos/os/rtthread/stm32f4xx/app/src/app_bak.c
deleted file mode 100644
index 6893426..0000000
--- a/demos/os/rtthread/stm32f4xx/app/src/app_bak.c
+++ /dev/null
@@ -1,57 +0,0 @@
-#include <ucos_ii.h>
-#include <cpu_core.h>
-#include <bsp.h>
-#include <cm_backtrace.h>
-#include <stdio.h>
-
-#define HARDWARE_VERSION               "V1.0.0"
-#define SOFTWARE_VERSION               "V0.1.0"
-
-static  OS_STK          AppTaskStartStk[APP_TASK_START_STK_SIZE];
-
-static void AppTaskStart(void *p_arg);
-extern void fault_test_by_unalign(void);
-extern void fault_test_by_div0(void);
-
-int main(void)
-{
-    INT8U err;
-    BSP_IntDisAll();
-    BSP_Init();
-    CPU_Init();
-    OSInit();
-    
-    /* CmBacktrace initialize */
-    cm_backtrace_init("CmBacktrace", HARDWARE_VERSION, SOFTWARE_VERSION);
-
-    OSTaskCreateExt((void (*)(void *)) AppTaskStart,
-                    (void           *) 0,
-                    (OS_STK         *)&AppTaskStartStk[APP_TASK_START_STK_SIZE - 1],
-                    (INT8U           ) APP_TASK_START_PRIO,
-                    (INT16U          ) APP_TASK_START_PRIO,
-                    (OS_STK         *)&AppTaskStartStk[0],
-                    (INT32U          ) APP_TASK_START_STK_SIZE,
-                    (void           *) 0,
-                    (INT16U          )(OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR));
-    
-    OSTaskNameSet(APP_TASK_START_PRIO, "app_start", &err);
-
-    printf("System initialize finish. Starting..\r\n");
-
-    OSStart();
-    
-    return (1);
-}
-
-static  void  AppTaskStart (void *p_arg)
-{
-//    fault_test_by_unalign();
-    fault_test_by_div0();
-
-    while (DEF_TRUE) {
-        LED_RUN_ON;
-        OSTimeDlyHMSM(0, 0, 0, 500);
-        LED_RUN_OFF;
-        OSTimeDlyHMSM(0, 0, 0, 500);
-    }
-}