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RIOT/cpu/nrf5x_common/clock.c 2.03 KB
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  /*
   * Copyright (C) 2017 Freie Universitรคt Berlin
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /**
   * @ingroup     cpu_nrf5x_common
   * @{
   *
   * @file
   * @brief       Clock initialization code
   *
   * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
   * @}
   */
  
  #include "cpu.h"
  #include "periph_conf.h"
  
  /* make sure both clocks are configured */
  #ifndef CLOCK_HFCLK
  #error "Clock init: CLOCK_HFCLK is not defined by your board!"
  #endif
  #ifndef CLOCK_LFCLK
  #error "Clock init: CLOCK_LFCLK is not defined by your board!"
  #endif
  
  void clock_init_hf(void)
  {
      /* for the nRF51 we can chose the XTAL frequency */
  #ifdef CPU_FAM_NRF51
  #if (CLOCK_HFCLK == 32)
      NRF_CLOCK->XTALFREQ = CLOCK_XTALFREQ_XTALFREQ_32MHz;
  #elif (CLOCK_HFCLK == 16)
      NRF_CLOCK->XTALFREQ = CLOCK_XTALFREQ_XTALFREQ_16MHz;
  #endif
  #endif
  
  #if CLOCK_HFCLK
      /* start the HF clock */
      NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
      NRF_CLOCK->TASKS_HFCLKSTART = 1;
      while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}
  #endif
  }
  
  void clock_start_lf(void)
  {
      /* abort if LF clock is already running */
      if (NRF_CLOCK->LFCLKSTAT & CLOCK_LFCLKSTAT_STATE_Msk) {
          return;
      }
  
  #if (CLOCK_LFCLK == 0)
      NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_RC);
  #elif (CLOCK_LFCLK == 1)
      NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_Xtal);
  #elif (CLOCK_LFCLK == 2)
      NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_Synth);
  #else
  #error "LFCLK init: CLOCK_LFCLK has invalid value"
  #endif
      /* enable LF clock */
      NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
      NRF_CLOCK->TASKS_LFCLKSTART = 1;
      while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0) {}
  
      /* calibrate the RC LF clock if applicable */
  #if (CLOCK_HFCLK && (CLOCK_LFCLK == 0))
      NRF_CLOCK->EVENTS_DONE = 0;
      NRF_CLOCK->TASKS_CAL = 1;
      while (NRF_CLOCK->EVENTS_DONE == 0) {}
  #endif
  }
  
  void clock_stop_lf(void)
  {
      NRF_CLOCK->TASKS_LFCLKSTOP = 1;
      while (NRF_CLOCK->LFCLKSTAT & CLOCK_LFCLKSTAT_STATE_Msk) {}
  }