text: /* mbed Microcontroller Library
   * Copyright (c) 2006-2018 ARM Limited
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #if DEVICE_USTICKER
  
  #include "hal/us_ticker_api.h"
  #include "us_ticker_defines.h"
  
  // This variable is set to 1 at the of mbed_sdk_init function.
  // The ticker_read_us function must not be called until the mbed_sdk_init is terminated.
  extern int mbed_sdk_inited;
  
  // Defined in us_ticker.c
  void init_16bit_timer(void);
  void init_32bit_timer(void);
  
  #if TIM_MST_BIT_WIDTH <= 16
  static uint16_t prev_time;
  #else
  static uint32_t prev_time;
  #endif
  static uint32_t total_ticks;
  static uint16_t prev_tick_remainder;
  
  // Overwrite default HAL functions defined as "weak"
  
  HAL_StatusTypeDef HAL_InitTick(uint32_t TickPriority)
  {
  #if TIM_MST_BIT_WIDTH == 16
      init_16bit_timer();
  #else
      init_32bit_timer();
  #endif
      return HAL_OK;
  }
  
  uint32_t HAL_GetTick()
  {
      uint32_t new_time = us_ticker_read();
      uint32_t elapsed_time = (((new_time - prev_time) & US_TICKER_MASK) + prev_tick_remainder);
      prev_time = new_time;
      uint32_t elapsed_ticks;
      // Speed optimisation for small time intervals, avoiding a potentially-slow C library divide.
      if (TIM_MST_BIT_WIDTH <= 16 || elapsed_time < 65536) {
          elapsed_ticks = 0;
          while (elapsed_time >= 1000) {
              elapsed_ticks++;
              elapsed_time -= 1000;
          }
          prev_tick_remainder = elapsed_time;
      } else {
          elapsed_ticks = elapsed_time / 1000;
          prev_tick_remainder = elapsed_time % 1000;
      }
      total_ticks += elapsed_ticks;
      return total_ticks;
  }
  
  void HAL_SuspendTick(void)
  {
      // Do nothing
  }
  
  void HAL_ResumeTick(void)
  {
      // Do nothing
  }
  
  #endif /* DEVICE_USTICKER */
  