Nucleo-F411RE （STM32F411）LL库体验 2 -sysclk的配置

1、Nucleo-F411RE 时钟源

Nucleo-F411RE开发版只有一个8M的晶振，看起来像是给st-link提供时钟的，所以猜测F411RE时钟的来源应该来自st-link（stm32F103c8t6）的mco输出。
在这里插入图片描述
mco输出频率为8M。
HSI频率为16M。

2、设置工作主频100M

a、采用HSE+PLL

假设mco输入频率8M，经过PLLM，4分频变成2M。然后经过PLLN，倍频100，变成200M，那么再经过
PLLP 2分频就可变成100M的时钟频率。
如果工作频率80M，那么就修改倍频80即可。
LL库代码如下：

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_HSE_PLL_100M_Config(void)
{  
    LL_FLASH_SetLatency(LL_FLASH_LATENCY_3);
    while(LL_FLASH_GetLatency()!= LL_FLASH_LATENCY_3)
    {
    }
    LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
    // while (LL_PWR_IsActiveFlag_VOS() == 0)
    // {
    // }
    LL_RCC_HSE_EnableBypass();
    LL_RCC_HSE_Enable();

    /* Wait till HSE is ready */
    while(LL_RCC_HSE_IsReady() != 1)
    {

    }
    LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_HSE, LL_RCC_PLLM_DIV_4, 100, LL_RCC_PLLP_DIV_2);
    LL_RCC_PLL_Enable();

    /* Wait till PLL is ready */
    while(LL_RCC_PLL_IsReady() != 1)
    {

    }
    LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
    LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_2);
    LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_1);
    LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_PLL);

    /* Wait till System clock is ready */
    while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_PLL)
    {

    }
    LL_Init1msTick(100000000);
    LL_SetSystemCoreClock(100000000);
    LL_RCC_SetTIMPrescaler(LL_RCC_TIM_PRESCALER_TWICE);
}

b、采用HSI+PLL的方式

HSI的频率为16M，假设经过PLLM 8分频变成2M，经过PLLN 100倍频变成200M，经过PLLP 2分频即可得到100M的工作频率。
如果想要设定80M工作频率，修改倍频80倍即可。
代码如下：

/**
 * HSI + PLL 100M
*/
void SystemClock_HSI_PLL_100M_Config(void)
{
    LL_FLASH_SetLatency(LL_FLASH_LATENCY_3);
    while(LL_FLASH_GetLatency()!= LL_FLASH_LATENCY_3)
    {
    }
    LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
    // while (LL_PWR_IsActiveFlag_VOS() == 0)
    // {
    // }
    LL_RCC_HSI_SetCalibTrimming(16);
    LL_RCC_HSI_Enable();

    /* Wait till HSI is ready */
    while(LL_RCC_HSI_IsReady() != 1)
    {

    }
    LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_HSI, LL_RCC_PLLM_DIV_8, 100, LL_RCC_PLLP_DIV_2);
    LL_RCC_PLL_Enable();

    /* Wait till PLL is ready */
    while(LL_RCC_PLL_IsReady() != 1)
    {

    }
    LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
    LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_2);
    LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_1);
    LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_PLL);

    /* Wait till System clock is ready */
    while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_PLL)
    {

    }
    LL_Init1msTick(100000000);
    LL_SetSystemCoreClock(100000000);
    LL_RCC_SetTIMPrescaler(LL_RCC_TIM_PRESCALER_TWICE);
}

3、不使用锁频环PLL

a、HSE最高8M工作主频

LL库设定代码如下：

/**
 * HSE提供信号，不经过pll倍频
*/
void SystemClock_HSE_8M_Config(void)
{
    LL_FLASH_SetLatency(LL_FLASH_LATENCY_0);
    while(LL_FLASH_GetLatency()!= LL_FLASH_LATENCY_0)
    {
    }
    LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
    // while (LL_PWR_IsActiveFlag_VOS() == 0)
    // {
    // }
    LL_RCC_HSE_EnableBypass();
    LL_RCC_HSE_Enable();

    /* Wait till HSE is ready */
    while(LL_RCC_HSE_IsReady() != 1)
    {

    }
    LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
    LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_2);
    LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_1);
    LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_HSE);

    /* Wait till System clock is ready */
    while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_HSE)
    {

    }
    LL_Init1msTick(8000000);
    LL_SetSystemCoreClock(8000000);
    LL_RCC_SetTIMPrescaler(LL_RCC_TIM_PRESCALER_TWICE);
}

b、HSL最高16M工作主频

LL库设定代码如下：

/**
 * HSI提供信号，不经过pll倍频
*/
void SystemClock_HSI_16M_Config(void)
{
    LL_FLASH_SetLatency(LL_FLASH_LATENCY_0);
    while(LL_FLASH_GetLatency()!= LL_FLASH_LATENCY_0)
    {
    }
    LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
    // while (LL_PWR_IsActiveFlag_VOS() == 0)
    // {
    // }
    LL_RCC_HSI_SetCalibTrimming(16);
    LL_RCC_HSI_Enable();

    /* Wait till HSI is ready */
    while(LL_RCC_HSI_IsReady() != 1)
    {

    }
    LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
    LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_2);
    LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_1);
    LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_HSI);

    /* Wait till System clock is ready */
    while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_HSI)
    {

    }
    LL_Init1msTick(16000000);
    LL_SetSystemCoreClock(16000000);
    LL_RCC_SetTIMPrescaler(LL_RCC_TIM_PRESCALER_TWICE);
}