add event-driven framework

see examples/event_driven_at_module and examples/event_driven_hello_world, demo project: TencentOS-tiny\board\TencentOS_tiny_EVB_MX\KEIL\event_driven_hello_world

kernel/evtdrv/include/tos_evtdrv_tick.h

@@ -0,0 +1,45 @@
+#ifndef _TOS_EVTDRV_TICK_H_
+#define  _TOS_EVTDRV_TICK_H_
+
+#if TOS_CFG_EVENT_DRIVEN_EN > 0u
+
+/**
+ * @brief Get the current systick cout.
+ *
+ * @attention
+ *
+ * @return  current systick count.
+ */
+__API__ evtdrv_tick_t tos_evtdrv_systick_get(void);
+
+/**
+ * @brief tick interrupt handler.
+ *
+ * @attention   if you wanna use event-driven timer, you must deal with the tick.
+ *
+ * @return  None.
+ */
+__API__ void tos_evtdrv_tick_handler(void);
+
+/**
+ * @brief Convert tick count to milli-seconds.
+ *
+ * @attention
+ *
+ * @return  the milli-seconds equals to the tick count.
+ */
+__API__ evtdrv_time_t tos_evtdrv_tick2millisec(evtdrv_tick_t tick);
+
+/**
+ * @brief Convert milli-seconds to tick count.
+ *
+ * @attention
+ *
+ * @return  the tick count equals to the tick count.
+ */
+__API__ evtdrv_tick_t tos_evtdrv_millisec2tick(evtdrv_time_t ms);
+
+#endif /* TOS_CFG_EVENT_DRIVEN_EN */
+
+#endif /* _TOS_EVTDRV_TICK_H_ */
+