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

  this demo is based on the at-start board, in this demo, pa7 input external
  signal,debug view to see frequency and dutycycle or use uasrt1 to see frequency
  and dutycycle(pa9:usart1_tx). 

  for more detailed information. please refer to the application note document AN0085.
