STM32一定时器产生不同频率的PWM

SPI1->

定时器中断中，根据这个参数，改变频率。

#include "stm32libstm32f10x.h"
#include "hal.h"
volatile u16 Key_Value=1000; //用于保存按键相应的PWM波占空比值
int main(void)
{
ChipHalInit();
ChipOutHalInit();
while(1)
{
if( (!Get_Key_Up)&(!Get_Key_Down)&(!Get_Key_Left)&(!Get_Key_Right)&(!Get_Key_Ctrl) )
{
Key_Value=12000;
}
else
{
if(Get_Key_Up) //按键前进按下 ,对应1kHz
{
Key_Value=6000;
}
else if(Get_Key_Down) //按键后退按下 ,对应2kHz
{
Key_Value=3000;
}
Delay_Ms(20); //10ms延时

if(Get_Key_Left) //按键左转按下,对应3kHz
{
Key_Value=2000;
}
else if(Get_Key_Right) //按键右转按下,对应4kHz
{
Key_Value=1500;
}
Delay_Ms(20); //10ms延时

if(Get_Key_Ctrl) //按键控制按下,对应5kHz
{
Key_Value=1200;
}
Delay_Ms(20); //10ms延时
}
}
}
extern volatile u16 Key_Value;
u16 capture=0;
void TIM3_IRQHandler(void)
{

if (TIM_GetITStatus(TIM3, TIM_IT_CC2) != RESET)
{
TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);
capture = TIM_GetCapture2(TIM3);
TIM_SetCompare2(TIM3, capture + Key_Value);
}
}
void TIM3_Configuration(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

TIM_TimeBaseStructure.TIM_Prescaler = 5; //预分频(时钟分频)72M/6=12M
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //向上计数
TIM_TimeBaseStructure.TIM_Period = 65535; //装载值选择最大
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_div1;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0x0;
TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle; //PWM模式2
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //正向通道有效
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;//反向通道无效
TIM_OCInitStructure.TIM_Pulse = Key_Value; //占空时间
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //输出极性
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High; //互补端的极性
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;

TIM_OC2Init(TIM3,&TIM_OCInitStructure); //通道2
TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Disable);

TIM_Cmd(TIM3,ENABLE);

//TIM_CtrlPWMOutputs(TIM1,ENABLE);
TIM_ITConfig(TIM3, TIM_IT_CC2 , ENABLE);
}

注意：在计算PWM频率的时候，TIMx的时钟都是72Mhz，分频后，因为翻转两次才能形成一个PWM波，因为，PWM的频率是捕获改变频率的1/2。