text: /*!
      \file  systick.c
      \brief the systick configuration file
  
      \version 2019-6-5, V1.0.0, firmware for GD32VF103
  */
  
  /*
      Copyright (c) 2019, GigaDevice Semiconductor Inc.
  
      Redistribution and use in source and binary forms, with or without modification, 
  are permitted provided that the following conditions are met:
  
      1. Redistributions of source code must retain the above copyright notice, this 
         list of conditions and the following disclaimer.
      2. Redistributions in binary form must reproduce the above copyright notice, 
         this list of conditions and the following disclaimer in the documentation 
         and/or other materials provided with the distribution.
      3. Neither the name of the copyright holder nor the names of its contributors 
         may be used to endorse or promote products derived from this software without 
         specific prior written permission.
  
      THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
  OF SUCH DAMAGE.
  */
  
  #include "gd32vf103.h"
  #include "systick.h"
  
  /*!
      \brief      delay a time in milliseconds
      \param[in]  count: count in milliseconds
      \param[out] none
      \retval     none
  */
  void delay_1ms(uint32_t count)
  {
  	uint64_t start_mtime, delta_mtime;
  
  	// Don't start measuruing until we see an mtime tick
  	uint64_t tmp = get_timer_value();
  	do {
  	start_mtime = get_timer_value();
  	} while (start_mtime == tmp);
  
  	do {
  	delta_mtime = get_timer_value() - start_mtime;
  	}while(delta_mtime <(SystemCoreClock/4000.0 *count ));
  }
  
  /*!
      \brief      delay a time in microseconds
      \param[in]  count: count in microseconds
      \param[out] none
      \retval     none
  */
  void delay_1us(uint32_t count) {
      uint64_t start_mtime, delta_mtime;
  
      // Don't start measuruing until we see an mtime tick
      uint64_t tmp = get_timer_value();
      do {
          start_mtime = get_timer_value();
      } while( start_mtime == tmp );
  
      do {
          delta_mtime = get_timer_value() - start_mtime;
      } while( delta_mtime < (SystemCoreClock/4000000.0 * count) );
  }
  
  /*!
      \brief      get start time for calculating elapsed ms later
      \param[in]  none
      \param[out] none
      \retval     current time
  */
  uint64_t start_elapse() 
  {
      return get_timer_value();
  }
  
  /*!
      \brief      delay count ms of time relative to start 
      \param[in]  start: time from get_start()
      \param[in]  count: time in ms
      \param[out] none
      \retval     ms actually waited
  */
  uint32_t elapse_1ms(uint64_t start, uint32_t count)
  {
      uint64_t wait = get_timer_value();
     	do {} while( (get_timer_value() - start) < (SystemCoreClock/4000.0 * count) ); 
      return ((get_timer_value() - wait) * 4000) / SystemCoreClock;
  }
  
  /*!
      \brief      elapsed ms relative to start 
      \param[in]  start: time from get_start()
      \param[out] none
      \retval     ms elapsed
  */
  uint32_t elapsed_1ms(uint64_t start)
  {
      return ((get_timer_value() - start) * 4000) / SystemCoreClock;
  }
  