www.pudn.com > RC522.zip > pwm.c, change:2012-03-08,size:2025b


#include "pwm.h" 
#include "led.h" 
 
void PWM_Init(u16 arr,u16 psc) 
{   
	GPIO_InitTypeDef GPIO_InitStructure; 
	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure; 
	TIM_OCInitTypeDef  TIM_OCInitStructure; 
 
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); 
 	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA  | RCC_APB2Periph_AFIO, ENABLE);  //使能GPIO外设和AFIO复用功能模块时钟使能 
		 	 //用于TIM3的CH2输出的PWM通过该LED显示 
					 
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; 
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; 
	GPIO_Init(GPIOA, &GPIO_InitStructure); 
 
	 	  //设置该引脚为复用输出功能,输出TIM3 CH2的PWM脉冲波形 
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7; //TIM_CH2 
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //复用推挽输出 
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
	GPIO_Init(GPIOA, &GPIO_InitStructure); 
	//GPIO_WriteBit(GPIOA, GPIO_Pin_7,Bit_SET); // PA7上拉	 
 
	TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值	 80K 
	TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置用来作为TIMx时钟频率除数的预分频值  不分频 
	TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim 
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIM向上计数模式 
	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位 
	 
  
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //选择定时器模式:TIM脉冲宽度调制模式2 
	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比较输出使能 
	TIM_OCInitStructure.TIM_Pulse = 0; //设置待装入捕获比较寄存器的脉冲值 
	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //输出极性:TIM输出比较极性高 
	TIM_OC2Init(TIM3, &TIM_OCInitStructure);  //根据TIM_OCInitStruct中指定的参数初始化外设TIMx 
	TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  //使能TIMx在CCR2上的预装载寄存器 
	 
	TIM_ARRPreloadConfig(TIM3, ENABLE); //使能TIMx在ARR上的预装载寄存器 
	 
	  
	TIM_Cmd(TIM3, ENABLE);  //使能TIMx外设 
  
 
}