/**
  **************************************************************************
  * @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, pa8 and pb6
  output pwm waveform.
  the master tmrer tmr1 is running at:
  tmr1 frequency = tmr1 counter clock / (tmr1_period + 1) = 1 mhz
  and the duty cycle is equal to: tmr1_ch1/(tmr1_pr + 1) = 50%

  the tmr3 is running at:
  (tmr1 frequency)/ ((tmr3 period +1)* (repetition_counter+1)) = 66.67 khz and
  a duty cycle equal to tmr3_ch1/(tmr3_pr + 1) = 33.3%

  the tmr4 is running at:
  (tmr1 frequency)/ ((tmr4 period +1)* (repetition_counter+1)) = 100 khz and
  a duty cycle equal to tmr4_ch1/(tmr4_pr + 1) = 50%
