nuttx/arch/arm/src/stm32/stm32_lsi.c

/****************************************************************************
 * arch/arm/src/stm32/stm32_lsi.c
 *
 *   Copyright (C) 2012, 2015 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.orgr>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include "up_arch.h"

#include "stm32_rcc.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: stm32_rcc_enablelsi
 *
 * Description:
 *   Enable the Internal Low-Speed (LSI) RC Oscillator.
 *
 ****************************************************************************/

void stm32_rcc_enablelsi(void)
{
  /* Enable the Internal Low-Speed (LSI) RC Oscillator by setting the LSION bit
   * the RCC CSR register.
   */

  modifyreg32(STM32_RCC_CSR, 0, RCC_CSR_LSION);

  /* Wait for the internal RC 40 kHz oscillator to be stable. */

  while ((getreg32(STM32_RCC_CSR) & RCC_CSR_LSIRDY) == 0);
}

/****************************************************************************
 * Name: stm32_rcc_disablelsi
 *
 * Description:
 *   Disable the Internal Low-Speed (LSI) RC Oscillator.
 *
 ****************************************************************************/

void stm32_rcc_disablelsi(void)
{
  /* Enable the Internal Low-Speed (LSI) RC Oscillator by setting the LSION bit
   * the RCC CSR register.
   */

  modifyreg32(STM32_RCC_CSR, RCC_CSR_LSION, 0);

  /* LSIRDY should go low after 3 LSI clock cycles */
}