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

  this demo is based on the ht32f49163_sk board, in this demo, 
  shows how to use the can filter funciton. the can tool transmit 6 specified 
  messages in total (3 extended-id messages and 3 standard-id messages), 
  when mcu receive one expect id message, test_result will add one, if test 
  success, only 4 filter messages will be received, the three leds will toggle.
  set-up
  - can tx      --->   pb9
  - can rx      --->   pb8
