/**
  **************************************************************************
  * @file     readme.txt
  * @version  v2.0.0
  * @date     2021-11-26
  * @brief    readme
  **************************************************************************
  */

  this demo is based on the at-start board, in this demo, pa6 pa7 pb0 pb1
  output waveform.
  cc1 overflow rate = tmr3 counter clock / ch1_val = 366.2 hz
  cc2 overflow rate = tmr3 counter clock / ch2_val = 732.4 hz
  cc3 overflow rate = tmr3 counter clock / ch3_val = 1464.8 hz
  cc4 overflow rate = tmr3 counter clock / ch4_val = 2929.6 hz 
