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

  this demo is based on the ht32f49395_sk board, in this demo, pa0, pa1, pa2 and
  pa3 output pwm waveform.
  in this case , ch1 ch2 ch3 ch4 frequency = tmr clock / (period+1) / (div+1)
  = 183 hz  systemclock = 192mhz
  ch1 duty_cycle = 50%
  ch2 duty_cycle = 25%
  ch3 duty_cycle = 12.5%
  ch4 duty_cycle = 6.25%
