cpu.c
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/*
* Copyright (C) 2015 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_ezr32wg
* @{
*
* @file
* @brief Implementation of the CPU initialization
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
* @}
*/
#include "cpu.h"
#include "periph_conf.h"
#include "periph/init.h"
/**
* @brief Configure clock sources and the CPU frequency
*
* On the ezr32wg cpu, we basically have two options for selecting the main
* clock source, using an external clock source (e.g. a crystal), or using the
* internal RC oscillator (enabled by default).
*/
static void clk_init(void)
{
/* reset the clock to it's default values */
CMU->CTRL = _CMU_CTRL_RESETVALUE;
#ifdef CLOCK_HFXO
/* configure clock system for external oscillator */
#if CLOCK_HFXO > 32000000
CMU->CTRL |= CMU_CTRL_HFXOBUFCUR_BOOSTABOVE32MHZ;
#endif
/* enable the oscillator */
CMU->OSCENCMD = CMU_OSCENCMD_HFXOEN;
/* wait for external oscillator to be stable */
while (!(CMU->STATUS & CMU_STATUS_HFXORDY));
/* switch to the external oscillator */
CMU->CMD = CMU_CMD_HFCLKSEL_HFXO;
/* wait until clock source is applied */
while (!(CMU->STATUS & CMU_STATUS_HFXOSEL));
#endif
/* set the core clock divider */
CMU->HFCORECLKDIV = (CLOCK_HFCORECLKDIV - 1);
/* configure the high speed peripheral clock: set divider and enable it */
CMU->HFPERCLKDIV = (CMU_HFPERCLKDIV_HFPERCLKEN | (CLOCK_HFPERCLKDIV - 1));
}
void cpu_init(void)
{
/* initialize the Cortex-M core */
cortexm_init();
/* Initialise clock sources and generic clocks */
clk_init();
/* trigger static peripheral initialization */
periph_init();
}