贴上代码

#include "stm32f10x.h"
#include "Usart.h"
#include "stdio.h"




//函数申明
void RCC_Configuration(void);
void TIM3_GPIO_Config(void);
void TIM3_Mode_Config(void);
** 函数名称: main
** 功能描述: 主函数入口
** 参数描述：

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
int main(void)
{

        RCC_Configuration();
        TIM3_GPIO_Config();
        TIM3_Mode_Config();
        while(1);  


}

void RCC_Configuration(void)
{
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB, ENABLE);
}
void TIM3_GPIO_Config(void)   
{  
  GPIO_InitTypeDef GPIO_InitStructure;  
  /*GPIOA Configuration: TIM3 channel 1 and 2 as alternate function push-pull */  
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_6 | GPIO_Pin_7;  
  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);  

  /*GPIOB Configuration: TIM3 channel 3 and 4 as alternate function push-pull */  
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_0 | GPIO_Pin_1;  
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;           // 复用推挽输出  
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  

  GPIO_Init(GPIOB, &GPIO_InitStructure);  
}  




void TIM3_Mode_Config(void)  
{  
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;  
    TIM_OCInitTypeDef  TIM_OCInitStructure;  

    /* PWM信号电平跳变值 */  
    u16 CCR1_Val = 500;         
    u16 CCR2_Val = 375;  
    u16 CCR3_Val = 250;  
    u16 CCR4_Val = 125;  

/* -----------------------------------------------------------------------
    TIM3 Configuration: generate 4 PWM signals with 4 different duty cycles:
    TIM3CLK = 36 MHz, Prescaler = 0x0, TIM3 counter clock = 36 MHz
    TIM3 ARR Register = 999 => TIM3 Frequency = TIM3 counter clock/(ARR + 1)
    TIM3 Frequency = 36 KHz.
    TIM3 Channel1 duty cycle = (TIM3_CCR1/ TIM3_ARR)* 100 = 50%
    TIM3 Channel2 duty cycle = (TIM3_CCR2/ TIM3_ARR)* 100 = 37.5%
    TIM3 Channel3 duty cycle = (TIM3_CCR3/ TIM3_ARR)* 100 = 25%
    TIM3 Channel4 duty cycle = (TIM3_CCR4/ TIM3_ARR)* 100 = 12.5%
  ----------------------------------------------------------------------- */  

  /* Time base configuration */        
  TIM_TimeBaseStructure.TIM_Period = 999;       //当定时器从0计数到999，即为1000次，为一个定时周期  
  TIM_TimeBaseStructure.TIM_Prescaler = 0;      //设置预分频：不预分频，即为36MHz  
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;  //设置时钟分频系数：不分频  
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //向上计数模式  

  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);  

  /* PWM1 Mode configuration: Channel1 */  
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;     //配置为PWM模式1  
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;   
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;  //当定时器计数值小于CCR1_Val时为高电平  

  TIM_OCInitStructure.TIM_Pulse = CCR1_Val;    //设置跳变值，当计数器计数到这个值时，电平发生跳变  
  TIM_OC1Init(TIM3, &TIM_OCInitStructure);   //使能通道1  
  TIM_OCInitStructure.TIM_Pulse = CCR2_Val;   //设置通道2的电平跳变值，输出另外一个占空比的PWM  
  TIM_OC2Init(TIM3, &TIM_OCInitStructure);    //使能通道2
  TIM_OCInitStructure.TIM_Pulse = CCR3_Val; //设置通道3的电平跳变值，输出另外一个占空比的PWM  
  TIM_OC3Init(TIM3, &TIM_OCInitStructure);   //使能通道3
  TIM_OCInitStructure.TIM_Pulse = CCR4_Val; //设置通道4的电平跳变值，输出另外一个占空比的PWM  
  TIM_OC4Init(TIM3, &TIM_OCInitStructure);  //使能通道4  


  //使能预装载寄存器
  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);  
  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  
  TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);  
  TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);  


// 使能TIM3重载寄存器ARR
TIM_ARRPreloadConfig(TIM3, ENABLE);     
TIM_Cmd(TIM3, ENABLE);                   //使能定时器3   

}


实测4个通道PWM频率只有8KHZ   按理说应该是36MHZ/1000=36kHZ.



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