stm32f4默认多少m时钟，stm32的sd卡实验的时钟怎么计算

1，stm32的sd卡实验的时钟怎么计算

APB最大频率是Mhz，这个在初始化的时候就已经设置了的，如果用库函数默认就是Mhz，在m

你说呢...

stm32的sd卡实验的时钟怎么计算

2，STM32 通用定时器时钟为什么是72M

如果是默认设置的话就是72M的最高是72M可以自己重新配置

STM32 通用定时器时钟为什么是72M

3，STM32F4的USB时钟必须工作在48MHZ吗如果不是48M会有什么问

如果不是48Musb是肯定无法正常通信的，单片机里面48M是usb正常工作的最低频率，而且其它频率必须是48M的整数倍，这是强制规定，如果不是那么usb与外界通信就不能同步，必然失败。

down in the corner of a wall.

STM32F4的USB时钟必须工作在48MHZ吗如果不是48M会有什么问

4，STM32的系统默认时钟是多少

/*!< At this stage the microcontroller clock setting is already configured, this is done through SystemInit() function which is called from startupfile (startup_stm32f10x_xx.s) before to branch to application main.To reconfigure the default setting of SystemInit() function, refer tosystem_stm32f10x.c file*/ 然后你再去看看 SystemInit()这个函数是怎么配置的吧。看完再说。这个是标准库里面的例程主函数里的第一句话。

5，STM32的运行速度到底是多少

这问题问得也太笼统了吧，你指的是系统运行速度吧？系统运行速度取决于系统时钟(sysclock)，以STM32F103来说，上电默认是使用内部的8MHz时钟(HSI)来运行，不过一般都会使用外部的8MHz时钟(HSE)经过倍频成72MHz作为系统时钟(sysclock)。

依据运行的频率，你就知道运行的速度了。不同型号的cpu有不同的最高频率。参考：http://www.st.com/web/en/catalog/mmc/FM141/SC1169有各类型cpu的参数。

TM32的GPIO模块最高可达到18MHz信号输出，SPI也能达到18MHz

6，stm32f407 初始时钟是多少怎么改

楼上的用起来也有点麻烦，用我这个吧，C文件：#include "stm32f4xx.h"#include "sysclk.h"unsigned char SysClockSet(unsigned char OSC, unsigned char Clock) unsigned int temp = 0, PLLM = 0, PLLN = 0, PLLP = 0, PLLQ = 0; unsigned int OSC_Sta; unsigned int OSC_VALUE = HSI_VALUE; unsigned int OSC_RDY = RCC_CR_HSIRDY; unsigned int OSC_ON = RCC_CR_HSION; unsigned char OSC_ERROR = HSI_error; unsigned int OSC_OK = HSI_OK; unsigned int OSC_SW = RCC_CFGR_SW_HSI; unsigned int OSC_SWS = RCC_CFGR_SWS_HSI; unsigned int OSC_SRC = RCC_PLLCFGR_PLLSRC_HSI; if(OSC == HSE) OSC_VALUE = HSE_VALUE; OSC_RDY = RCC_CR_HSERDY; OSC_ON = RCC_CR_HSEON; OSC_ERROR = HSE_error; OSC_OK = HSE_OK; OSC_SW = RCC_CFGR_SW_HSE; OSC_SWS = RCC_CFGR_SWS_HSE; OSC_SRC = RCC_PLLCFGR_PLLSRC_HSE; } else if(OSC != HSI) return(Parameter_error); switch (Clock) case 0 : PLLM = (OSC_VALUE/1000000); PLLN = 96; PLLP = 8; PLLQ = 2; break; //12MHz case 1 : PLLM = (OSC_VALUE/1000000); PLLN = 96; PLLP = 6; PLLQ = 2; break; //16MHz case 2 : PLLM = (OSC_VALUE/2000000); PLLN = 72; PLLP = 8; PLLQ = 3; break; //18MHz case 3 : PLLM = (OSC_VALUE/2000000); PLLN = 96; PLLP = 8; PLLQ = 4; break; //24MHz case 4 : PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 8; PLLQ = 5; break; //30MHz case 5 : PLLM = (OSC_VALUE/2000000); PLLN = 96; PLLP = 6; PLLQ = 4; break; //32MHz case 6 : PLLM = (OSC_VALUE/2000000); PLLN = 144; PLLP = 8; PLLQ = 6; break; //36MHz case 7 : PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 6; PLLQ = 5; break; //40MHz case 8 : PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 8; PLLQ = 7; break; //42MHz case 9 : PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 8; PLLQ = 8; break; //48MHz case 10: PLLM = (OSC_VALUE/2000000); PLLN = 216; PLLP = 8; PLLQ = 9; break; //54MHz case 11: PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 6; PLLQ = 7; break; //56MHz case 12: PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 4; PLLQ = 5; break; //60MHz case 13: PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 6; PLLQ = 8; break; //64MHz case 14: PLLM = (OSC_VALUE/2000000); PLLN = 144; PLLP = 4; PLLQ = 6; break; //72MHz case 15: PLLM = (OSC_VALUE/2000000); PLLN = 240; PLLP = 6; PLLQ = 10; break; //80MHz case 16: PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 4; PLLQ = 7; break; //84MHz case 17: PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 4; PLLQ = 8; break; //96MHz case 18: PLLM = (OSC_VALUE/2000000); PLLN = 216; PLLP = 4; PLLQ = 9; break; //108MHz case 19: PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 2; PLLQ = 5; break; //120MHz case 20: PLLM = (OSC_VALUE/2000000); PLLN = 144; PLLP = 2; PLLQ = 6; break; //144MHz case 21: PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 2; PLLQ = 7; break; //168MHz case 22: PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 2; PLLQ = 8; break; //192MHz case 23: PLLM = (OSC_VALUE/2000000); PLLN = 216; PLLP = 2; PLLQ = 9; break; //216MHz case 24: PLLM = (OSC_VALUE/2000000); PLLN = 240; PLLP = 2; PLLQ = 10; break; //240MHz// case 25: PLLM = (OSC_VALUE/2000000); PLLN = 260; PLLP = 2; PLLQ = 11; break; //260MHz default: PLLM = (OSC_VALUE/2000000); PLLN = 240; PLLP = 2; PLLQ = 10; break; //240MHz } //如果时钟没有稳定，则重新启动时钟并等待稳定 OSC_Sta = RCC->CR & OSC_RDY; if(OSC_Sta == 0) RCC->CR |= OSC_ON; do OSC_Sta = RCC->CR & OSC_RDY; temp++; }while((OSC_Sta == 0) && (temp < 0x0600)); if(OSC_Sta == 0)return(OSC_ERROR); //超时错误 } //切换系统时钟为对应晶振并等待稳定 RCC->CFGR &= (~(RCC_CFGR_SW)); RCC->CFGR |= OSC_SW; while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS ) != OSC_SWS); //配置PLL RCC->CR &= (~(RCC_CR_PLLON)); //先关闭PLL RCC->CR &= (~(RCC_CR_PLLI2SON)); //关闭PLLI2S RCC->PLLCFGR = PLLM | (PLLN << 6) | (((PLLP >> 1) -1) << 16) | (PLLQ << 24) | (OSC_SRC); //启用PLL，并等待稳定 RCC->CR |= RCC_CR_PLLON; while((RCC->CR & RCC_CR_PLLRDY) == 0); //启用PLLI2S，并等待稳定 RCC->CR |= RCC_CR_PLLI2SON; while((RCC->CR & RCC_CR_PLLI2SRDY) == 0); //切换系统时钟为PLL并等待稳定 RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW)); RCC->CFGR |= RCC_CFGR_SW_PLL; while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS ) != RCC_CFGR_SWS_PLL); return(OSC_OK); }uint32_t SysClockGet(void) uint32_t PLLM = 0, PLLN = 0, PLLP = 0, PLLSRC = 0; if ((RCC->CFGR & RCC_CFGR_SWS ) == RCC_CFGR_SWS_HSE) return HSE_VALUE; else if ((RCC->CFGR & RCC_CFGR_SWS ) == RCC_CFGR_SWS_HSI) return HSI_VALUE; else PLLM = RCC->PLLCFGR & RCC_PLLCFGR_PLLM; PLLN = ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN)>>6); PLLP = ((((RCC->PLLCFGR & RCC_PLLCFGR_PLLP)>>16)+1)<<1); PLLSRC = RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC; if(PLLSRC == 0) return (((HSI_VALUE * PLLN) / PLLM )/ PLLP); else return (((HSE_VALUE * PLLN) / PLLM )/ PLLP); }}

7，stm32默认时钟是多少

stm32F1系类最大72Mhz 你可以超频用但是不一定能稳定可靠工作比方说你用8M晶振配置按照72M主频算，直接换成10M晶振主频自然就是 90MFlash Leancy 设到最大应该可以比72Mhz 高一些，另外 APB1分频要小于等于36MHz，要用usb的话必须是48或72

stm32系统的时钟一般有三种hsi,内部高速时钟,默认8mhz,如果你的程序不做任何处理,系统默认的就是8mhz,还有外部晶振或者外部时钟,普通型最大不超过16mhz,互联型不超过25mhz,还有一个pll,从hsi或者hse里吸取时钟,倍频成最大72mhz综述,如果你的程序不做任何处理,就是8mh是

8，对于单片机来说时钟的作用是什么stm32f4的系统时钟最高可以达

做如下检查:第一,如果你用的是systeminit....且是用的库,就是xxxx.lib,那么,你就不必修改了,因为库已经写死8m.第二,如果你是用的仿真,那么要修改keil的配置,keil默认配置是8m,你下载到flash里不受keil配置的影响,但是如果你软件仿真,是受keil的影响建议:如果你的外晶振不是8m的,不要调用systeminit函数来初始化你的时钟,自己写比较好.

“一个周期采样24个点”你应该是需要在一个正弦周期内均匀采样24个点吧，那么每83.3ms采集一次数据即可，单次采集的数据根本都不需要踢DMA啊。你列的第一种方法我甚至都怀疑ADC的时钟频率能不能降到这么低。

9，stm32f4的系统时钟怎么配置

初始化后无时钟，是因为你没有在clock里面为你的spi0或者spi1配置时钟。

如何使用stm32f4的dsp库我们平常所使用的cpu为定点cpu，意思是进行整点数值运算的cpu。当遇到形如1.1+1.1的浮点数运算时，定点cpu就遇到大难题了。对于32位单片机，利用q化处理能发挥他本身的性能，但是精度和速度仍然不会提高很多。现在设计出了一个新的cpu，叫做fpu，这个芯片专门处理浮点数的运算，这样处理器就将整点数和浮点数分开来处理，整点数交由定点cpu处理而浮点数交由fpu处理。我们见到过ti的dsp，还有stm32f4系列的带有dsp功能的微控制器。前者笔者没有用过，不作评论，而后者如果需要用到fpu的浮点运算功能，必须要进行一些必要的设置。首先，由于浮点运算在fpu中进行，所以首先应该使能fpu运行。在system_init()中，定义__fpu_present和__fpu_used/* fpu settings------------------------------------------------------------*/ #if (__fpu_present == 1)&& (__fpu_used == 1) scb->cpacr |= ((3ul<< 10*2)|(3ul << 11*2)); /*set cp10 and cp11 full access */ #endif这样就使能了fpu。对于上述改变，当程序中出现这种简单的加减乘除运算fpu就起作用了。但是对于复杂的如三角运算、开方运算等，我们就需要加入math.h头文件。但是如果单纯的加入他，那么keil会自动调用内部的math.h，该头文件是针对arm处理器的，专门用于定点cpu和标准算法（ieee-754）。对于使用了fpu的stm32f4是没有任何作用的。所以，需要将math.h换成st的库，即arm_math.h。在该头文件中，涉及到另一个文件core_cmx.h（x=0、3、4），当然了，如同stm32f1系列一样，在工程中加入core_cm4.h即可。到这里，算是全部设置完毕，之差最后一步，调用！但是别小看了这一步，因为如果调用的不正确，全面的设置就白费了。在使用三角函数如sin()、cos()时不要直接写如上形式，因为他们函数的名字来自于math.h，所以你调用的仍旧是keil库中的标准math.h。要使用arm_math.h中的arm_sin_f32()函数（见line.5780，原函数见dsp_lib\source\fastmathfunctions），可以看到他利用的是三次样条插值法快速求值（见line.263 /* cubic interpolation process */）。注意一下例外函数，sqrt()，在arm_math.h中为arm_sqrt_f32()。使用他的时候需要同时开启#if(__fpu_used == 1) && defined ( __cc_arm )才行，切记！还可以发现开方函数还有q15和q31之分，我想他们的区别就是精度的问题，但是他们没有应用fpu来计算，说白了就是利用0x5f3759df这个数进行快速开方

10，stm32f407 初始时钟是多少怎么改

STM32启动时默认为内部RC震荡所以在使用的时候，首先要对时钟进行初始化等待外部晶振稳定后然后才对外部晶振进行分频或者倍频最后才是对APB总线时钟及模块时钟进行配置。

楼上的用起来也有点麻烦，用我这个吧，C文件：#include "stm32f4xx.h"#include "sysclk.h"unsigned char SysClockSet(unsigned char OSC, unsigned char Clock) unsigned int temp = 0, PLLM = 0, PLLN = 0, PLLP = 0, PLLQ = 0; unsigned int OSC_Sta; unsigned int OSC_VALUE = HSI_VALUE; unsigned int OSC_RDY = RCC_CR_HSIRDY; unsigned int OSC_ON = RCC_CR_HSION; unsigned char OSC_ERROR = HSI_error; unsigned int OSC_OK = HSI_OK; unsigned int OSC_SW = RCC_CFGR_SW_HSI; unsigned int OSC_SWS = RCC_CFGR_SWS_HSI; unsigned int OSC_SRC = RCC_PLLCFGR_PLLSRC_HSI; if(OSC == HSE) OSC_VALUE = HSE_VALUE; OSC_RDY = RCC_CR_HSERDY; OSC_ON = RCC_CR_HSEON; OSC_ERROR = HSE_error; OSC_OK = HSE_OK; OSC_SW = RCC_CFGR_SW_HSE; OSC_SWS = RCC_CFGR_SWS_HSE; OSC_SRC = RCC_PLLCFGR_PLLSRC_HSE; } else if(OSC != HSI) return(Parameter_error); switch (Clock) case 0 : PLLM = (OSC_VALUE/1000000); PLLN = 96; PLLP = 8; PLLQ = 2; break; //12MHz case 1 : PLLM = (OSC_VALUE/1000000); PLLN = 96; PLLP = 6; PLLQ = 2; break; //16MHz case 2 : PLLM = (OSC_VALUE/2000000); PLLN = 72; PLLP = 8; PLLQ = 3; break; //18MHz case 3 : PLLM = (OSC_VALUE/2000000); PLLN = 96; PLLP = 8; PLLQ = 4; break; //24MHz case 4 : PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 8; PLLQ = 5; break; //30MHz case 5 : PLLM = (OSC_VALUE/2000000); PLLN = 96; PLLP = 6; PLLQ = 4; break; //32MHz case 6 : PLLM = (OSC_VALUE/2000000); PLLN = 144; PLLP = 8; PLLQ = 6; break; //36MHz case 7 : PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 6; PLLQ = 5; break; //40MHz case 8 : PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 8; PLLQ = 7; break; //42MHz case 9 : PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 8; PLLQ = 8; break; //48MHz case 10: PLLM = (OSC_VALUE/2000000); PLLN = 216; PLLP = 8; PLLQ = 9; break; //54MHz case 11: PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 6; PLLQ = 7; break; //56MHz case 12: PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 4; PLLQ = 5; break; //60MHz case 13: PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 6; PLLQ = 8; break; //64MHz case 14: PLLM = (OSC_VALUE/2000000); PLLN = 144; PLLP = 4; PLLQ = 6; break; //72MHz case 15: PLLM = (OSC_VALUE/2000000); PLLN = 240; PLLP = 6; PLLQ = 10; break; //80MHz case 16: PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 4; PLLQ = 7; break; //84MHz case 17: PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 4; PLLQ = 8; break; //96MHz case 18: PLLM = (OSC_VALUE/2000000); PLLN = 216; PLLP = 4; PLLQ = 9; break; //108MHz case 19: PLLM = (OSC_VALUE/2000000); PLLN = 120; PLLP = 2; PLLQ = 5; break; //120MHz case 20: PLLM = (OSC_VALUE/2000000); PLLN = 144; PLLP = 2; PLLQ = 6; break; //144MHz case 21: PLLM = (OSC_VALUE/2000000); PLLN = 168; PLLP = 2; PLLQ = 7; break; //168MHz case 22: PLLM = (OSC_VALUE/2000000); PLLN = 192; PLLP = 2; PLLQ = 8; break; //192MHz case 23: PLLM = (OSC_VALUE/2000000); PLLN = 216; PLLP = 2; PLLQ = 9; break; //216MHz case 24: PLLM = (OSC_VALUE/2000000); PLLN = 240; PLLP = 2; PLLQ = 10; break; //240MHz// case 25: PLLM = (OSC_VALUE/2000000); PLLN = 260; PLLP = 2; PLLQ = 11; break; //260MHz default: PLLM = (OSC_VALUE/2000000); PLLN = 240; PLLP = 2; PLLQ = 10; break; //240MHz } //如果时钟没有稳定，则重新启动时钟并等待稳定 OSC_Sta = RCC->CR & OSC_RDY; if(OSC_Sta == 0) RCC->CR |= OSC_ON; do OSC_Sta = RCC->CR & OSC_RDY; temp++; }while((OSC_Sta == 0) && (temp < 0x0600)); if(OSC_Sta == 0)return(OSC_ERROR); //超时错误 } //切换系统时钟为对应晶振并等待稳定 RCC->CFGR &= (~(RCC_CFGR_SW)); RCC->CFGR |= OSC_SW; while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS ) != OSC_SWS); //配置PLL RCC->CR &= (~(RCC_CR_PLLON)); //先关闭PLL RCC->CR &= (~(RCC_CR_PLLI2SON)); //关闭PLLI2S RCC->PLLCFGR = PLLM | (PLLN << 6) | (((PLLP >> 1) -1) << 16) | (PLLQ << 24) | (OSC_SRC); //启用PLL，并等待稳定 RCC->CR |= RCC_CR_PLLON; while((RCC->CR & RCC_CR_PLLRDY) == 0); //启用PLLI2S，并等待稳定 RCC->CR |= RCC_CR_PLLI2SON; while((RCC->CR & RCC_CR_PLLI2SRDY) == 0); //切换系统时钟为PLL并等待稳定 RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW)); RCC->CFGR |= RCC_CFGR_SW_PLL; while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS ) != RCC_CFGR_SWS_PLL); return(OSC_OK);}uint32_t SysClockGet(void) uint32_t PLLM = 0, PLLN = 0, PLLP = 0, PLLSRC = 0; if ((RCC->CFGR & RCC_CFGR_SWS ) == RCC_CFGR_SWS_HSE) return HSE_VALUE; else if ((RCC->CFGR & RCC_CFGR_SWS ) == RCC_CFGR_SWS_HSI) return HSI_VALUE; else PLLM = RCC->PLLCFGR & RCC_PLLCFGR_PLLM; PLLN = ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN)>>6); PLLP = ((((RCC->PLLCFGR & RCC_PLLCFGR_PLLP)>>16)+1)<<1); PLLSRC = RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC; if(PLLSRC == 0) return (((HSI_VALUE * PLLN) / PLLM )/ PLLP); else return (((HSE_VALUE * PLLN) / PLLM )/ PLLP); }}