void GPIO_TimPWM(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA , ENABLE);//

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7; //TIM_CH2 GPIOA_Pin_7輸出

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //復(fù)用推挽輸出

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure); //不解釋
}

void TIM3_Configuration(void)

{

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

TIM_OCInitTypeDef TIM_OCInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //使能TIM3

//假如我要產(chǎn)生50Hz占空比為50%的PWM波，方便控制舵機(jī)

//設(shè)置方法：

//系統(tǒng)默認(rèn)時(shí)鐘為72MHz，預(yù)分頻71+1次，得到TIM3計(jì)數(shù)時(shí)鐘為1MHz
//計(jì)數(shù)長(zhǎng)度為19999+1=20000，可得PWM頻率為1M/20000=50Hz

//具體設(shè)置可參考上面的設(shè)置方法，簡(jiǎn)單明了！

TIM_TimeBaseStructure.TIM_Prescaler =72-1;//網(wǎng)上多數(shù)設(shè)置有誤

TIM_TimeBaseStructure.TIM_Period =20000-1;

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;

//設(shè)置時(shí)鐘分割:TIM_CKD_DIV1 = 0，PWM波不延時(shí)（延時(shí)破壞占空比？待考證）

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM向上計(jì)數(shù)模式

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

TIM_ARRPreloadConfig(TIM3, DISABLE); //禁止ARR預(yù)裝載緩沖器,也可以不用設(shè)置

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //選擇定時(shí)器模式:TIM脈沖寬度調(diào)制模式2

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比較輸出使能

//占空比設(shè)置方法：

//占空比=(TIM_Pulse+1)/(TIM_Pulse+1)-(TIM_Period+1)=10000/20000=0.5=50%

TIM_OCInitStructure.TIM_Pulse =10000-1;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //輸出極性:TIM輸出比較極性高

TIM_OC2Init(TIM3, &TIM_OCInitStructure); //根據(jù)TIM_OCInitStruct中指定的參數(shù)初始化外設(shè)TIMx

TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable); //使能TIMx在CCR2上的預(yù)裝載寄存器

//上面兩句中的OC2確定了是channle幾，要是OC3則是channel 3

TIM_CtrlPWMOutputs(TIM3,ENABLE); //設(shè)置TIM2的PWM輸出為使能

TIM_ARRPreloadConfig(TIM3, ENABLE); //使能TIMx在ARR上的預(yù)裝載寄存器

TIM_Cmd(TIM3, ENABLE); //使能TIMx外設(shè)

}

int main(void)

{

GPIO_TimPWM();

TIM3_Configuration();

while(1)

{

} ;

}

利用Keil邏輯分析儀分分析PWM波形圖：經(jīng)過(guò)測(cè)試可以看出輸出波形精度可靠！