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Merge pull request #4156 from DipSwitch/add_clock_selection_stm32f0

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cpu: Add clock source selection based on CLOCK_HSE or CLOCK_HSI for STM32F0 family
This commit is contained in:
Peter Kietzmann 2016-03-30 09:33:54 +02:00
commit 1756e9e270
1 changed files with 33 additions and 11 deletions
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44
cpu/stm32f0/cpu.c
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@ -20,6 +20,28 @@
#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);
@ -53,11 +75,6 @@ void cpu_init(void)
*/
static void clock_init(void)
{
/* configure the HSE clock */
/* enable the HSI clock */
RCC->CR |= RCC_CR_HSION;
/* reset clock configuration register */
RCC->CFGR = 0;
RCC->CFGR2 = 0;
@ -68,11 +85,11 @@ static void clock_init(void)
/* disable all clock interrupts */
RCC->CIR = 0;
/* enable the HSE clock */
RCC->CR |= RCC_CR_HSEON;
/* enable the high speed clock source */
RCC->CR |= CLOCK_CR_SOURCE;
/* wait for HSE to be ready */
while (!(RCC->CR & RCC_CR_HSERDY)) {}
/* wait for the high speed clock to be ready */
while (!(RCC->CR & CLOCK_CR_SOURCE_RDY)) {}
/* setup the peripheral bus prescalers */
@ -86,8 +103,7 @@ static void clock_init(void)
/* reset PLL configuration bits */
RCC->CFGR &= ~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLMUL);
/* set PLL configuration */
RCC->CFGR |= RCC_CFGR_PLLSRC_HSE_PREDIV | RCC_CFGR_PLLXTPRE_HSE_PREDIV_DIV1 |
(((CLOCK_PLL_MUL - 2) & 0xf) << 18);
RCC->CFGR |= CLOCK_PLL_SOURCE | ((((CLOCK_PLL_MUL * CLOCK_PLL_MUL_MUL) - 2) & 0xf) << 18);
/* enable PLL again */
RCC->CR |= RCC_CR_PLLON;
@ -107,4 +123,10 @@ static void clock_init(void)
/* 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
}