/**
  **************************************************************************
  * @file     readme.txt
  * @brief    readme
  **************************************************************************
  */

  this demo is based on the ht32f49163_sk board, in this demo, shows how to use
  software trigger exint.
  software trigger will be generate in tmr1 overflow interrupt.
  led2 toggle means tmr1 overflow interrupt respond.
  led3 and led4 toggle means exint line 4  interrupt respond.
