/**
  **************************************************************************
  * @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, provides a description
  of how to use a dma channel to transfer a halfword data buffer from embedded
  sram memory to gpiob and gpiob0~gpiob15 output the data of data buffer. dma2
  channel1 is configured to transfer the contents of a 16-halfword data buffer
  stored in embedded sram memory to the gpiob. if transfer full data, the three 
  leds will turn on, and dma2 enabled the flexible function. user can use logic
  analyzer get waveform.
