diff --git a/boards/board.c b/boards/board.c
index 75529f3a9..fa28a557c 100644
--- a/boards/board.c
+++ b/boards/board.c
@@ -71,11 +71,19 @@ void led_blinking_set_interval(uint32_t ms)
   led_blink_interval_ms = ms;
 }
 
+tusb_error_t led_blinking_subtask(void);
 void led_blinking_task(void* param)
 {
   (void) param;
 
   OSAL_TASK_LOOP_BEGIN
+  led_blinking_subtask();
+  OSAL_TASK_LOOP_END
+}
+
+tusb_error_t led_blinking_subtask(void)
+{
+  OSAL_SUBTASK_BEGIN
 
   static uint32_t led_on_mask = 0;
 
@@ -92,7 +100,7 @@ void led_blinking_task(void* param)
 //    if ( BIT_TEST_(btn_mask, i) ) printf("button %d is pressed\n", i);
 //  }
 
-  OSAL_TASK_LOOP_END
+  OSAL_SUBTASK_END
 }
 
 // TODO remove legacy cmsis code
diff --git a/demos/device/src/app_os_prio.h b/demos/device/src/app_os_prio.h
index 52d42efe3..5d932a41e 100644
--- a/demos/device/src/app_os_prio.h
+++ b/demos/device/src/app_os_prio.h
@@ -50,8 +50,6 @@
   #define LOWER_PRIO(x)   0   // does not matter
 #elif TUSB_CFG_OS == TUSB_OS_FREERTOS
   #define LOWER_PRIO(x)   ((x)-1) // freeRTOS lower number --> lower priority
-#elif TUSB_CFG_OS == TUSB_OS_CMSIS_RTX
-  #define LOWER_PRIO(x)   ((x)-1) // CMSIS-RTOS lower number --> lower priority
 #else
   #error Priority is not configured for this RTOS
 #endif
diff --git a/demos/device/src/main.c b/demos/device/src/main.c
index de6250529..bb26d0368 100644
--- a/demos/device/src/main.c
+++ b/demos/device/src/main.c
@@ -79,10 +79,6 @@ void os_none_start_scheduler(void)
 
 int main(void)
 {
-#if TUSB_CFG_OS == TUSB_OS_CMSIS_RTX
-  osKernelInitialize(); // CMSIS RTX requires kernel init before any other OS functions
-#endif
-
   board_init();
   print_greeting();
 
@@ -101,8 +97,6 @@ int main(void)
   vTaskStartScheduler();
 #elif TUSB_CFG_OS == TUSB_OS_NONE
   os_none_start_scheduler();
-#elif TUSB_CFG_OS == TUSB_OS_CMSIS_RTX
-  osKernelStart();
 #else
   #error need to start RTOS schduler
 #endif
@@ -119,7 +113,6 @@ void print_greeting(void)
   {
       [TUSB_OS_NONE]      = "None",
       [TUSB_OS_FREERTOS]  = "FreeRTOS",
-      [TUSB_OS_CMSIS_RTX] = "CMSIS-RTX"
   };
 
   printf("\n\
diff --git a/tinyusb/osal/osal.h b/tinyusb/osal/osal.h
index 9f7a2b320..4f2fdad22 100644
--- a/tinyusb/osal/osal.h
+++ b/tinyusb/osal/osal.h
@@ -51,8 +51,6 @@
  *  @{ */
 #define TUSB_OS_NONE       1 ///< No RTOS is used
 #define TUSB_OS_FREERTOS   2 ///< FreeRTOS is used
-#define TUSB_OS_CMSIS_RTX  3 ///< CMSIS RTX is used
-#define TUSB_OS_UCOS3      4 ///< MicroC OS III is used (not supported yet)
 /** @} */
 
 #include "tusb_option.h"
@@ -71,8 +69,6 @@ static inline bool osal_task_create(osal_func_t code, const char* name, uint32_t
 #else
    #if TUSB_CFG_OS == TUSB_OS_FREERTOS
     #include "osal_freeRTOS.h"
-  #elif TUSB_CFG_OS == TUSB_OS_CMSIS_RTX
-    #include "osal_cmsis_rtx.h"
   #else
     #error TUSB_CFG_OS is not defined or OS is not supported yet
   #endif
diff --git a/tinyusb/osal/osal_freeRTOS.h b/tinyusb/osal/osal_freeRTOS.h
index 363aa1863..d8d42c033 100644
--- a/tinyusb/osal/osal_freeRTOS.h
+++ b/tinyusb/osal/osal_freeRTOS.h
@@ -69,7 +69,6 @@ static inline bool osal_task_create(osal_func_t code, const char* name, uint32_t
   return xTaskCreate(code, (const signed char*) name, stack_size, param, prio, task_hdl);
 }
 
-static inline void osal_task_delay(uint32_t msec) ATTR_ALWAYS_INLINE;
 static inline void osal_task_delay(uint32_t msec)
 {
   vTaskDelay( (TUSB_CFG_TICKS_HZ * msec) / 1000 );