clock.c
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/*
* Copyright (C) 2017 Freie Universität 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) {}
}