void SYSCLK_Config_HSI_64Mhz(void)
{
__IO uint32_t StartUpCounter = 0, HSIStatus = 0;
/* SYSCLK, HCLK, PCLK2 and PCLK1 configuration ---------------------------*/
/* Enable HSI */
RCC->CR |= ((uint32_t)RCC_CR_HSION);
/* Wait till HSI is ready and if Time out is reached exit */
do
{
HSIStatus = RCC->CR & RCC_CR_HSIRDY;
StartUpCounter++;
} while((HSIStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));
if ((RCC->CR & RCC_CR_HSIRDY) != RESET)
{
HSIStatus = (uint32_t)0x01;
}
else
{
HSIStatus = (uint32_t)0x00;
}
if (HSIStatus == (uint32_t)0x01)
{
/* Enable Prefetch Buffer */
FLASH->ACR |= FLASH_ACR_PRFTBE;
/* Flash 2 wait state */
FLASH->ACR &= (uint32_t)((uint32_t)~FLASH_ACR_LATENCY);
FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_1;
/* HCLK = SYSCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;
/* PCLK2 = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;
/* PCLK1 = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV2;
/* Clear PLL Source [16] and Multiplier [21:18] bits */
RCC->CFGR &= ~(RCC_CFGR_PLLMULL | RCC_CFGR_PLLSRC);
/* PLL configuration: PLLCLK = HSI / 2 * 16 = 64 MHz */
RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_HSI_Div2 | RCC_CFGR_PLLMULL16);
/* 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)((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) != (uint32_t)0x08)
{
}
}
else
{ /* If HSE fails to start-up, the application will have wrong clock
configuration. User can add here some code to deal with this error */
}
}
