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RIOT/cpu/saml21/cpu.c 2.2 KB
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  /*
   * Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
   *               2015 FreshTemp, LLC.
   *
   * 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_saml21
   * @{
   *
   * @file        cpu.c
   * @brief       Implementation of the CPU initialization for Atmel SAML21 MCUs
   *
   * @author      Kaspar Schleiser <kaspar@schleiser.de>
   * @}
   */
  
  #include "cpu.h"
  #include "periph/init.h"
  
  static void _gclk_setup(int gclk, uint32_t reg)
  {
      while (GCLK->SYNCBUSY.reg & GCLK_SYNCBUSY_GENCTRL(gclk)) {}
      GCLK->GENCTRL[gclk].reg = reg;
  }
  
  /**
   * @brief Initialize the CPU, set IRQ priorities, clocks
   */
  void cpu_init(void)
  {
      /* disable the watchdog timer */
      WDT->CTRLA.bit.ENABLE = 0;
  
      /* initialize the Cortex-M core */
      cortexm_init();
  
      /* turn on only needed APB peripherals */
      MCLK->APBAMASK.reg =
          MCLK_APBAMASK_PM
          |MCLK_APBAMASK_MCLK
          |MCLK_APBAMASK_RSTC
          |MCLK_APBAMASK_OSCCTRL
          |MCLK_APBAMASK_OSC32KCTRL
          |MCLK_APBAMASK_SUPC
          |MCLK_APBAMASK_GCLK
          |MCLK_APBAMASK_WDT
          |MCLK_APBAMASK_RTC
          |MCLK_APBAMASK_EIC
          |MCLK_APBAMASK_PORT
          //|MCLK_APBAMASK_TAL
          ;
  
      /* Software reset the GCLK module to ensure it is re-initialized correctly */
      GCLK->CTRLA.reg = GCLK_CTRLA_SWRST;
      while (GCLK->CTRLA.reg & GCLK_CTRLA_SWRST) {}
      while (GCLK->SYNCBUSY.reg & GCLK_SYNCBUSY_SWRST) {}
  
      /* set OSC16M to 16MHz */
      OSCCTRL->OSC16MCTRL.bit.FSEL = 3;
      OSCCTRL->OSC16MCTRL.bit.ONDEMAND = 0;
      OSCCTRL->OSC16MCTRL.bit.RUNSTDBY = 0;
  
      /* Setup GCLK generators */
      _gclk_setup(0, GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_OSC16M);
      _gclk_setup(1, GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_OSCULP32K);
  
  #ifdef FEATURE_PERIPH_PM
      /* enable power managemet module */
      MCLK->APBAMASK.reg |= MCLK_APBAMASK_PM;
      PM->CTRLA.reg = PM_CTRLA_MASK & (~PM_CTRLA_IORET);
  
      /* disable brownout detection
       * (Caused unexplicable reboots from sleep on saml21. /KS)
       */
      SUPC->BOD33.bit.ENABLE=0;
  #endif
  
      /* trigger static peripheral initialization */
      periph_init();
  }