系统时钟的重要性不要我多说,呵呵,在操作系统中特别重要,夜深了,我也不多说了,要睡觉了,呵呵,以后有空跑个ucos再发文章了,最近比较忙,呵呵
#include "stm32f10x_lib.h" void RCC_Configuration(void); void GPIO_Configuration(void); void NVIC_Configuration(void); void SysTick_Config(void); void Delay_Ms(u32); void TimingDelay_Decrement(void);
static vu32 TimingDelay;
/******************************************************************************* * Function Name : main * Description : Main program. * Input : None * Output : None * Return : None *******************************************************************************/ int main(void) { #ifdef DEBUG debug(); #endif RCC_Configuration();//配置系统时钟 NVIC_Configuration(); //配置 NVIC 和 Vector Table GPIO_Configuration(); //配置使用的GPIO口 SysTick_Config(); //主循环 while (1) { // 每隔1S钟就点亮一次LED Delay_Ms(500); GPIO_SetBits(GPIOB, GPIO_Pin_12); Delay_Ms(500); GPIO_ResetBits(GPIOB, GPIO_Pin_12);
} } //SysTick设置 void SysTick_Config(void) { /* Disable SysTick Counter */ SysTick_CounterCmd(SysTick_Counter_Disable); /* Disable the SysTick Interrupt */ SysTick_ITConfig(DISABLE); /* Configure HCLK clock as SysTick clock source */ SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8);
/* SysTick interrupt each 1000 Hz with HCLK equal to 72MHz */ SysTick_SetReload(9000);
/* Enable the SysTick Interrupt */ SysTick_ITConfig(ENABLE);
} void Delay_Ms(u32 nTime) { /* Enable the SysTick Counter */ SysTick_CounterCmd(SysTick_Counter_Enable); TimingDelay = nTime;
while(TimingDelay);
} void TimingDelay_Decrement(void) { if (TimingDelay) TimingDelay--; } void RCC_Configuration(void) { ErrorStatus HSEStartUpStatus; RCC_DeInit();//将外设 RCC寄存器重设为缺省值 RCC_HSEConfig(RCC_HSE_ON); //设置外部高速晶振(HSE) HSEStartUpStatus = RCC_WaitForHSEStartUp();//等待 HSE 起振
if(HSEStartUpStatus == SUCCESS) { FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable); //预取指缓存使能
FLASH_SetLatency(FLASH_Latency_2);//设置代码延时值 FLASH_Latency_2 2 延时周期 RCC_HCLKConfig(RCC_SYSCLK_Div1);//设置 AHB 时钟(HCLK)RCC_SYSCLK_Div1 AHB 时钟 = 系统时钟 RCC_PCLK2Config(RCC_HCLK_Div1); //设置高速 AHB 时钟(PCLK2)RCC_HCLK_Div2 APB1 时钟 = HCLK / 2 RCC_PCLK1Config(RCC_HCLK_Div2); //设置低速 AHB 时钟(PCLK1)RCC_HCLK_Div2 APB1 时钟 = HCLK / 2
RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9); // PLLCLK = 8MHz * 9 = 72 MHz 设置 PLL 时钟源及倍频系数
RCC_PLLCmd(ENABLE);//使能或者失能 PLL
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET) //等待指定的 RCC 标志位设置成功 等待PLL初始化成功 { } RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK); //设置系统时钟(SYSCLK) 设置PLL为系统时钟源 while(RCC_GetSYSCLKSource() != 0x08) //等待PLL成功用作于系统时钟的时钟源 0x00:HSI 作为系统时钟 0x04:HSE作为系统时钟 0x08:PLL作为系统时钟 { } } RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE); //使能或者失能 APB2 外设时钟 } void GPIO_Configuration(void) { GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_OD; GPIO_Init(GPIOB, &GPIO_InitStructure);
} void NVIC_Configuration(void) { #ifdef VECT_TAB_RAM /* Set the Vector Table base location at 0x20000000 */ NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0); #else /* VECT_TAB_FLASH */ /* Set the Vector Table base location at 0x08000000 */ NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0); #endif }
void delay() { int i; for (i=0; i<0xffff; i++) ; }
#ifdef DEBUG void assert_failed(u8* file, u32 line) { while (1) { } } #endif
|