实验的STM32型号:
STM32F103C8T6 48引脚
涉及到的知识:
RCC,GPIO,TIMER,PWM 设置
*RCC需打开外部时钟
*GPIO查表得知 PA3 默认复用引脚 TIM2_CH4
*TIMER使用默认的TIM2_CH4
*PWM的控制使用了动态的占空比来达到呼吸效果
下面给出代码:
- #include "stm32f10x.h"
- void RCC_cfg(void);
- void GPIO_cfg(void);
- void TIMER_cfg(void);
- void PWM_cfg(void);
- int led_fx=1;
- int led_dt=0;
- void delay_ms(u16 time)
- {
- u16 i=0;
- while(time--)
- {
- i=12000;
- while(i--) ;
- }
- }
- int main(void)
- {
- RCC_cfg();
- GPIO_cfg();
- TIMER_cfg();
- PWM_cfg();
- //使能TIM2计时器,开始输出PWM
- TIM_Cmd(TIM2, ENABLE);
- while(1)
- {
- delay_ms(5);
- if(led_fx==1)
- {
- led_dt++;
- }
- else
- {
- led_dt--;
- }
- if(led_dt>500) led_fx=0;
- if(led_dt==0) led_fx=1;
- TIM_SetCompare4(TIM2,led_dt);
- }
- }
- void RCC_cfg(void)
- {
- //定义错误状态变量
- ErrorStatus HSEStartUpStatus;
- //将RCC寄存器重新设置为默认值
- RCC_DeInit();
- //打开外部高速时钟晶振
- RCC_HSEConfig(RCC_HSE_ON);
- //等待外部高速时钟晶振工作
- HSEStartUpStatus = RCC_WaitForHSEStartUp();
- if(HSEStartUpStatus == SUCCESS)
- {
- //设置AHB时钟(HCLK)为系统时钟
- RCC_HCLKConfig(RCC_SYSCLK_Div1);
- //设置高速AHB时钟(APB2)为HCLK时钟
- RCC_PCLK2Config(RCC_HCLK_Div1);
- //设置低速AHB时钟(APB1)为HCLK的2分频
- RCC_PCLK1Config(RCC_HCLK_Div2);
- //设置FLASH代码延时
- FLASH_SetLatency(FLASH_Latency_2);
- //使能预取指缓存
- FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
- //设置PLL时钟,为HSE的9倍频 8MHz * 9 = 72MHz
- RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);
- //使能PLL
- RCC_PLLCmd(ENABLE);
- //等待PLL准备就绪
- while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET);
- //设置PLL为系统时钟源
- RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
- //判断PLL是否是系统时钟
- while(RCC_GetSYSCLKSource() != 0x08);
- }
- //开启TIM2的时钟
- RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
- //开启GPIOB的时钟和复用功能
- RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO,ENABLE);
- }
- void GPIO_cfg(void)
- {
- GPIO_InitTypeDef GPIO_InitStructure;
- // GPIO_PinRemapConfig(GPIO_PartialRemap1_TIM2, ENABLE); //映射引脚,默认PA3 ->TIM2_CH4因此不用映射
- //选择引脚3
- GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
- //输出频率最大50MHz
- GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
- //复用推挽输出
- GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
- //PA
- GPIO_Init(GPIOA,&GPIO_InitStructure);
- }
- void TIMER_cfg(void)
- {
- TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
- //重新将Timer设置为缺省值
- TIM_DeInit(TIM2);
- //采用内部时钟给TIM2提供时钟源
- TIM_InternalClockConfig(TIM2);
- //预分频系数为0
- TIM_TimeBaseStructure.TIM_Prescaler = 0;
- //设置计数溢出大小
- TIM_TimeBaseStructure.TIM_Period = 500;
- //设置计数器模式为向上计数模式(+1)
- TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
- //设置时钟分割
- TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
- //将配置应用到TIM2中
- TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);
- }
- void PWM_cfg(void)
- {
- TIM_OCInitTypeDef TimOCInitStructure;
- //设置缺省值
- TIM_OCStructInit(&TimOCInitStructure);
- //PWM模式1输出
- TimOCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
- //设置占空比 (Led亮度)
- TimOCInitStructure.TIM_Pulse = 0;
- //TIM输出比较极性高
- TimOCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
- //使能输出状态
- TimOCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
- //TIM2的CH4输出
- TIM_OC4Init(TIM2, &TimOCInitStructure);
- //设置TIM2的PWM输出为使能
- TIM_CtrlPWMOutputs(TIM2,ENABLE);
- }
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