用F407的官方库初始化各个始终都是多少啊？？？？

happy

 *=============================================================================
  *=============================================================================
  *        Supported STM32F4xx device revision    | Rev A
  *-----------------------------------------------------------------------------
  *        System Clock source                    | PLL (HSE)
  *-----------------------------------------------------------------------------
  *        SYSCLK(Hz)                             | 168000000
  *-----------------------------------------------------------------------------
  *        HCLK(Hz)                               | 168000000
  *-----------------------------------------------------------------------------
  *        AHB Prescaler                          | 1
  *-----------------------------------------------------------------------------
  *        APB1 Prescaler                         | 4
  *-----------------------------------------------------------------------------
  *        APB2 Prescaler                         | 2
  *-----------------------------------------------------------------------------
  *        HSE Frequency(Hz)                      | 25000000
  *-----------------------------------------------------------------------------
  *        PLL_M                                  | 25
  *-----------------------------------------------------------------------------
  *        PLL_N                                  | 336
  *-----------------------------------------------------------------------------
  *        PLL_P                                  | 2
  *-----------------------------------------------------------------------------
  *        PLL_Q                                  | 7
  *-----------------------------------------------------------------------------
  *        PLLI2S_N                               | NA
  *-----------------------------------------------------------------------------
  *        PLLI2S_R                               | NA
  *-----------------------------------------------------------------------------
  *        I2S input clock                        | NA
  *-----------------------------------------------------------------------------
  *        VDD(V)                                 | 3.3
  *-----------------------------------------------------------------------------
  *        Main regulator output voltage          | Scale1 mode
  *-----------------------------------------------------------------------------
  *        Flash Latency(WS)                      | 5
  *-----------------------------------------------------------------------------
  *        Prefetch Buffer                        | OFF
  *-----------------------------------------------------------------------------
  *        Instruction cache                      | ON
  *-----------------------------------------------------------------------------
  *        Data cache                             | ON
  *-----------------------------------------------------------------------------
  *        Require 48MHz for USB OTG FS,          | Enabled
  *        SDIO and RNG clock                     |                                 什么意思

正点原子

这个F4的时钟系统比较复杂,你得好好看看资料了.
我写了个通用点的函数:
//时钟设置函数
//Fvco=Fs*(plln/pllm);
//Fsys=Fvco/pllp=Fs*(plln/(pllm*pllp));
//Fusb=Fvco/pllq=Fs*(plln/(pllm*pllq));

//Fvco:VCO频率
//Fsys:系统时钟频率
//Fusb:USB,SDIO,RNG等的时钟频率
//FsLL输入时钟频率,可以是HSI,HSE等. 
//plln:主PLL倍频系数(PLL倍频),取值范围:64~432.
//pllm:主PLL和音频PLL分频系数(PLL之前的分频),取值范围:2~63.
//pllp:系统时钟的主PLL分频系数(PLL之后的分频),取值范围:2,4,6,8.(仅限这4个值!)
//pllq:USB/SDIO/随机数产生器等的主PLL分频系数(PLL之后的分频),取值范围:2~15.

//外部晶振为8M的时候,推荐值:plln=336,pllm=8,pllp=2,pllq=7.
//得到:Fvco=8*(336/8)=336Mhz
//     Fsys=336/2=168Mhz
//     Fusb=336/7=48Mhz
u8 Sys_Clock_Set(u32 plln,u32 pllm,u32 pllp,u32 pllq)
{ 
u16 retry=0;
u8 status=0;
RCC->CR|=1<<16; //HSE 开启 
while(((RCC->CR&(1<<17))==0)&&(retry<0X1FFF))retry++;//等待HSE RDY
if(retry==0X1FFF)status=1; //HSE无法就绪
else   
{
  RCC->APB1ENR|=1<<28; //电源接口时钟使能
PWR->CR|=3<<14;  //高性能模式,时钟可到168Mhz
RCC->CFGR|=(0<<4)|(5<<10)|(4<<13);//HCLK 不分频;APB1 4分频;APB2 2分频. 
//RCC->CR&=~(1<<24); //关闭主PLL
RCC->LLCFGR=pllm|(plln<<6)|(((pllp>>1)-1)<<16)|(pllq<<24)|(1<<22);//配置主PLL,PLL时钟源来自HSE
RCC->CR|=1<<24; //打开主PLL
while((RCC->CR&(1<<25))==0);//等待PLL准备好 
FLASH->ACR|=1<<9; //指令cache使能.
FLASH->ACR|=1<<10; //数据cache使能.
FLASH->ACR|=5<<0; //5个CPU等待周期. 
RCC->CFGR&=~(3<<0); //清零
RCC->CFGR|=2<<0; //选择主PLL作为系统时钟  
while((RCC->CFGR&(3<<2))!=(2<<2));//等待主PLL作为系统时钟成功. 
} 
return status;
}

调用的时候:
Stm32_Clock_Init(336,8,2,7); //设置时钟

就设置MCU运行在168Mhz了,且USB时钟是48Mhz

happy

回复【2楼】正点原子:
---------------------------------
确实是麻烦了，我看了框图，比10x的要多几个倍频和分频，多了一个锁相环，而且倍数要求比较搞笑，不想10x的

正点原子

回复【3楼】happy:
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这样实际是为IIS考虑的.