Update doxygen comments. Add TIM init for delayUs

src/os2/startup.cpp

@@ -36,7 +36,11 @@ extern "C"
 #ifdef STA_OS2_WATCHDOG_ENABLE
 		// Start timers
 		sta::startWatchdogTimer();
-#endif
+#endif // STA_OS2_WATCHDOG_ENABLE
+
+#ifdef STA_HAL_DELAY_US_TIM
+		HAL_TIM_Base_Start(&STA_HAL_DELAY_US_TIM);
+#endif // STA_HAL_DELAY_US_TIM
 
 		// Wake tasks
 		sta::signalStartupEvent();