cpu.c
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/*
* Copyright (C) 2014 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_stm32l1
* @{
*
* @file
* @brief Implementation of the kernel cpu functions
*
* @author Thomas Eichinger <thomas.eichinger@fu-berlin.de>
* @author Nick van IJzendoorn <nijzendoorn@engineering-spirit.nl>
*
* @}
*/
#include "cpu.h"
#include "board.h"
#include "periph_conf.h"
/* Check the source to be used for the PLL */
#if defined(CLOCK_HSI) && defined(CLOCK_HSE)
#error "Only provide one of two CLOCK_HSI/CLOCK_HSE"
#elif CLOCK_HSI
#define CLOCK_CR_SOURCE RCC_CR_HSION
#define CLOCK_CR_SOURCE_RDY RCC_CR_HSIRDY
#define CLOCK_PLL_SOURCE RCC_CFGR_PLLSRC_HSI
#elif CLOCK_HSE
#define CLOCK_CR_SOURCE RCC_CR_HSEON
#define CLOCK_CR_SOURCE_RDY RCC_CR_HSERDY
#define CLOCK_PLL_SOURCE RCC_CFGR_PLLSRC_HSE
#else
#error "Please provide CLOCK_HSI or CLOCK_HSE in boards/NAME/includes/perhip_cpu.h"
#endif
static void clk_init(void);
void cpu_init(void)
{
/* initialize the Cortex-M core */
cortexm_init();
/* initialize system clocks */
clk_init();
}
/**
* @brief Configure the clock system of the stm32f1
*/
static void clk_init(void)
{
/* Reset the RCC clock configuration to the default reset state(for debug purpose) */
/* Set MSION bit */
RCC->CR |= RCC_CR_MSION;
/* Reset SW, HPRE, PPRE1, PPRE2, MCOSEL and MCOPRE bits */
RCC->CFGR &= ~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLDIV | RCC_CFGR_PLLMUL);
/* Reset HSION, HSEON, CSSON and PLLON bits */
RCC->CR &= ~(RCC_CR_HSION | RCC_CR_HSEON | RCC_CR_HSEBYP | RCC_CR_CSSON | RCC_CR_PLLON);
/* Disable all interrupts */
RCC->CIR = 0x0;
/* SYSCLK, HCLK, PCLK2 and PCLK1 configuration */
/* Enable high speed clock source */
RCC->CR |= CLOCK_CR_SOURCE;
/* Wait till the high speed clock source is ready
* NOTE: the MCU will stay here forever if you use an external clock source and it's not connected */
while (!(RCC->CR & CLOCK_CR_SOURCE_RDY)) {}
FLASH->ACR |= FLASH_ACR_ACC64;
/* Enable Prefetch Buffer */
FLASH->ACR |= FLASH_ACR_PRFTEN;
/* Flash 1 wait state */
FLASH->ACR |= CLOCK_FLASH_LATENCY;
/* Power enable */
periph_clk_en(APB1, RCC_APB1ENR_PWREN);
/* Select the Voltage Range 1 (1.8 V) */
PWR->CR = PWR_CR_VOS_0;
/* Wait Until the Voltage Regulator is ready */
while((PWR->CSR & PWR_CSR_VOSF) != 0) {}
/* HCLK = SYSCLK */
RCC->CFGR |= (uint32_t)CLOCK_AHB_DIV;
/* PCLK2 = HCLK */
RCC->CFGR |= (uint32_t)CLOCK_APB2_DIV;
/* PCLK1 = HCLK */
RCC->CFGR |= (uint32_t)CLOCK_APB1_DIV;
/* PLL configuration: PLLCLK = CLOCK_SOURCE / PLL_DIV * PLL_MUL */
RCC->CFGR &= ~((uint32_t)(RCC_CFGR_PLLSRC | RCC_CFGR_PLLDIV | RCC_CFGR_PLLMUL));
RCC->CFGR |= (uint32_t)(CLOCK_PLL_SOURCE | CLOCK_PLL_DIV | CLOCK_PLL_MUL);
/* Enable PLL */
RCC->CR |= RCC_CR_PLLON;
/* Wait till PLL is ready */
while ((RCC->CR & RCC_CR_PLLRDY) == 0) {}
/* Select PLL as system clock source */
RCC->CFGR &= ~((uint32_t)(RCC_CFGR_SW));
RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL;
/* Wait till PLL is used as system clock source */
while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != RCC_CFGR_SWS_PLL) {}
}