/**
  **************************************************************************
  * @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, shows how to use
  the tmr peripheral to measure the frequency of an external signal.
  the minimum frequency value to measure is 2.93 khz(192m/65536).
  set-up
  - connect the external signal to measure to the tim3 ch2 pin (pa7).    
