STM32 RCC实验MCO脚输出时钟波形

2016-10-10 来源：eefocus

一：rcc设置使用内部HSI时钟，SYSclk 64M MCO输出32M

1：

void RCC_Configuration(void)

{

ErrorStatus HSEStartUpStatus;

/* RCC system reset(for debug purpose) */

RCC_DeInit(); //??RCC?????÷?è?????±????

/* Enable HSE */

//RCC_HSEConfig(RCC_HSE_ON); //?è???????????§??

RCC_HSEConfig(RCC_HSE_OFF);

RCC_HSICmd(ENABLE); //??????

//RCC_HSICmd(DISABLE); //??????

/* Wait till HSE is ready */ //HSE ?????????§??

//HSEStartUpStatus = RCC_WaitForHSEStartUp(); //????HSE????

while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY) == RESET)

{

}

// if(HSEStartUpStatus == SUCCESS)

// {

/* HCLK = SYSCLK *///?è??AHB?±??=?????±?? ?¨RCC_SYSCLK_Div1??·?????????

RCC_HCLKConfig(RCC_SYSCLK_Div1);

/* PCLK2 = HCLK *///?è??????APB2?±??(×??ó72MHZ)

RCC_PCLK2Config(RCC_HCLK_Div1); //RCC_HCLK_Div1 ??·?????RCC_HCLK_Div2 2·???

/* PCLK1 = HCLK/2 *///?è??????APB1?±???¨×??ó36MHZ??

RCC_PCLK1Config(RCC_HCLK_Div2);

/* Flash 2 wait state */

FLASH_SetLatency(FLASH_Latency_2);

/* Enable Prefetch Buffer */

FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);

/* PLLCLK = 8MHz * 9 = 72 MHz */

//RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);

//?????±????8/2=4M 4*16 = 64 hsi = 64m (MAX)

RCC_PLLConfig(RCC_PLLSource_HSI_Div2 , RCC_PLLMul_16);

/* Enable PLL */

RCC_PLLCmd(ENABLE);

/* Wait till PLL is ready */

while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)

{

}

/* Select PLL as system clock source */

RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

/* Wait till PLL is used as system clock source */

while(RCC_GetSYSCLKSource() != 0x08)

{

}

// }

}

2：设置MCO引脚PA8

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP ;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // ×???????????50MHz

GPIO_Init(GPIOA, &GPIO_InitStructure);

注意： A8引脚使用复用推挽输出模式，我使用推挽输出的时候波形没出来，推挽输出只能输出TTL，复用推挽可以输出时钟波形

3：设置MCO模式

RCC_MCOConfig(RCC_MCO_PLLCLK_Div2); //因为端口最大50M所以要PLL 2分频

二：rcc设置使用外部HSE时钟，SYSclk 72M MCO输出36M

只要改变RCC设置即可，其他不变

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STM32 RCC实 MCO脚时钟波形

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