fb11e647
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reseau statique a...
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/*
* Copyright (C) 2014 Freie Universitรคt 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_stm32f0
* @{
*
* @file
* @brief Implementation of the CPU initialization
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
* @}
*/
#include "cpu.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_DIV2)
#define CLOCK_PLL_MUL_MUL 2
#define CLOCK_DISABLE_HSI 0
#if (RCC_PLL_MUL * RCC_PLL_MUL_MUL) > 6
#error PLL with HSI as clock source cant extend 6 times multiplier
#endif
#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_PREDIV | RCC_CFGR_PLLXTPRE_HSE_PREDIV_DIV1)
#define CLOCK_PLL_MUL_MUL 1
#define CLOCK_DISABLE_HSI 1
#else
#error "Please provide CLOCK_HSI or CLOCK_HSE in boards/NAME/includes/perhip_cpu.h"
#endif
static void clock_init(void);
/**
* @brief Initialize the CPU, set IRQ priorities
*/
void cpu_init(void)
{
/* initialize the Cortex-M core */
cortexm_init();
/* initialize the clock system */
clock_init();
}
/**
* @brief Configure the controllers clock system
*
* The clock initialization make the following assumptions:
* - the external HSE clock from an external oscillator is used as base clock
* - the internal PLL circuit is used for clock refinement
*
* Use the following formulas to calculate the needed values:
*
* SYSCLK = ((HSE_VALUE / CLOCK_PLL_M) * CLOCK_PLL_N) / CLOCK_PLL_P
* USB, SDIO and RNG Clock = ((HSE_VALUE / CLOCK_PLL_M) * CLOCK_PLL_N) / CLOCK_PLL_Q
*
* The actual used values are specified in the board's `periph_conf.h` file.
*
* NOTE: currently there is not timeout for initialization of PLL and other locks
* -> when wrong values are chosen, the initialization could stall
*/
static void clock_init(void)
{
/* reset clock configuration register */
RCC->CFGR = 0;
RCC->CFGR2 = 0;
/* disable HSE, CSS and PLL */
RCC->CR &= ~(RCC_CR_HSEON | RCC_CR_HSEBYP | RCC_CR_CSSON | RCC_CR_PLLON);
/* disable all clock interrupts */
RCC->CIR = 0;
/* enable the high speed clock source */
RCC->CR |= CLOCK_CR_SOURCE;
/* wait for the high speed clock to be ready */
while (!(RCC->CR & CLOCK_CR_SOURCE_RDY)) {}
/* setup the peripheral bus prescalers */
/* set HCLK = SYSCLK, so no clock division here */
RCC->CFGR |= RCC_CFGR_HPRE_DIV1;
/* set PCLK = HCLK, so its not divided */
RCC->CFGR |= RCC_CFGR_PPRE_DIV1;
/* configure the PLL */
/* reset PLL configuration bits */
RCC->CFGR &= ~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLMUL);
/* set PLL configuration */
RCC->CFGR |= CLOCK_PLL_SOURCE | ((((CLOCK_PLL_MUL * CLOCK_PLL_MUL_MUL) - 2) & 0xf) << 18);
/* enable PLL again */
RCC->CR |= RCC_CR_PLLON;
/* wait until PLL is stable */
while(!(RCC->CR & RCC_CR_PLLRDY)) {}
/* configure flash latency */
/* enable pre-fetch buffer and set flash latency to 1 cycle*/
FLASH->ACR = FLASH_ACR_PRFTBE | FLASH_ACR_LATENCY;
/* configure the sysclock and the peripheral clocks */
/* set sysclock to be driven by the PLL clock */
RCC->CFGR &= ~RCC_CFGR_SW;
RCC->CFGR |= RCC_CFGR_SW_PLL;
/* wait for sysclock to be stable */
while (!(RCC->CFGR & RCC_CFGR_SWS_PLL)) {}
#if CLOCK_DISABLE_HSI
/* disable the HSI if we use the HSE */
RCC->CR &= ~(RCC_CR_HSION);
while (RCC->CR & RCC_CR_HSIRDY) {}
#endif
}
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