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

  this demo is based on the ht32f49041_sk board  , in this demo, 
  shows how to use the can loopback mode. every 1s transmit one message 
  and the led4 blink, if the message can be received, led2 blink.
  set-up
  - can tx      --->   pb9
  - can rx      --->   pb8

