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66 lines
1.8 KiB
C
66 lines
1.8 KiB
C
/*
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* Copyright (C) 2015 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup cpu_ezr32wg
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* @{
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*
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* @file
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* @brief Implementation of the CPU initialization
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*
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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* @}
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*/
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#include "cpu.h"
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#include "periph_conf.h"
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#include "periph/init.h"
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/**
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* @brief Configure clock sources and the CPU frequency
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*
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* On the ezr32wg cpu, we basically have two options for selecting the main
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* clock source, using an external clock source (e.g. a crystal), or using the
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* internal RC oscillator (enabled by default).
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*/
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static void clk_init(void)
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{
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/* reset the clock to it's default values */
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CMU->CTRL = _CMU_CTRL_RESETVALUE;
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#ifdef CLOCK_HFXO
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/* configure clock system for external oscillator */
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#if CLOCK_HFXO > 32000000
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CMU->CTRL |= CMU_CTRL_HFXOBUFCUR_BOOSTABOVE32MHZ;
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#endif
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/* enable the oscillator */
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CMU->OSCENCMD = CMU_OSCENCMD_HFXOEN;
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/* wait for external oscillator to be stable */
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while (!(CMU->STATUS & CMU_STATUS_HFXORDY));
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/* switch to the external oscillator */
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CMU->CMD = CMU_CMD_HFCLKSEL_HFXO;
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/* wait until clock source is applied */
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while (!(CMU->STATUS & CMU_STATUS_HFXOSEL));
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#endif
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/* set the core clock divider */
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CMU->HFCORECLKDIV = (CLOCK_HFCORECLKDIV - 1);
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/* configure the high speed peripheral clock: set divider and enable it */
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CMU->HFPERCLKDIV = (CMU_HFPERCLKDIV_HFPERCLKEN | (CLOCK_HFPERCLKDIV - 1));
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}
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void cpu_init(void)
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{
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/* initialize the Cortex-M core */
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cortexm_init();
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/* Initialise clock sources and generic clocks */
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clk_init();
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/* trigger static peripheral initialization */
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periph_init();
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}
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