STM32 TIM8初始化的配置與通用定時(shí)器的配置不同，我最開始時(shí)按照通用定時(shí)器配置，無論是配置一個(gè)通道，還是配置所有通道，死活不出來pwm。接著查資料說要添加這一句代碼：TIM_CtrlPWMOutputs(TIM8,ENABLE)，添加后只有通道4有輸出，其它三路沒有輸出，但是還是有點(diǎn)小激動(dòng)啊。后來看到一個(gè)網(wǎng)友說要添加下面幾行代碼：TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;

TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;

TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset;

添加后果然四路PWM均正常輸出。我測試后其實(shí)只要添加：TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;就可正常輸出pwm，感謝萬能度娘。

我還發(fā)現(xiàn)輸出的pwm波形與TIM_OCIdleState設(shè)置的狀態(tài)成和TIM_OCPolarity設(shè)置的極性相關(guān)，例如：TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low ; 時(shí)波形的占空比若為25%；那么：TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High ; 時(shí)波形的占空比為75%；

TIM8還有很多沒有搞明白的地方，需要繼續(xù)學(xué)習(xí)哥只是個(gè)傳說。最后附上TIM8的初始化代碼（注釋忽略）：

void TIM8_PWM_Init(u16 arr,u16 psc)

{

GPIO_InitTypeDef GPIO_InitStructure;

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

TIM_OCInitTypeDef TIM_OCInitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8, ENABLE);//使能定時(shí)器3時(shí)鐘

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE); //使能GPIO外設(shè)和AFIO復(fù)用功能模塊時(shí)鐘

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6|GPIO_Pin_7|GPIO_Pin_8|GPIO_Pin_9; //TIM_CH2

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

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOC, &GPIO_InitStructure);//初始化GPIO

//初始化TIM8

TIM_TimeBaseStructure.TIM_Period = arr; //設(shè)置在下一個(gè)更新事件裝入活動(dòng)的自動(dòng)重裝載寄存器周期的值

TIM_TimeBaseStructure.TIM_Prescaler =psc; //設(shè)置用來作為TIMx時(shí)鐘頻率除數(shù)的預(yù)分頻值

TIM_TimeBaseStructure.TIM_ClockDivision = 0; //設(shè)置時(shí)鐘分割:TDTS = Tck_tim

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

TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure); //根據(jù)TIM_TimeBaseInitStruct中指定的參數(shù)初始化TIMx的時(shí)間基數(shù)單位

//初始化TIM8 Channel2 PWM模式

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

TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;

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

TIM_OC1Init(TIM8, &TIM_OCInitStructure); //根據(jù)T指定的參數(shù)初始化外設(shè)TIM8 OC2

TIM_OC1PreloadConfig(TIM8, TIM_OCPreload_Enable); //使能TIM8在CCR2上的預(yù)裝載寄存器

TIM_SetCompare1(TIM8,474);

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

TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;

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

TIM_OC2Init(TIM8, &TIM_OCInitStructure); //根據(jù)T指定的參數(shù)初始化外設(shè)TIM8 OC2

TIM_OC2PreloadConfig(TIM8, TIM_OCPreload_Enable); //使能TIM8在CCR2上的預(yù)裝載寄存器

TIM_SetCompare2(TIM8,700);

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

TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;

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

TIM_OC3Init(TIM8, &TIM_OCInitStructure); //根據(jù)T指定的參數(shù)初始化外設(shè)TIM8 OC2

TIM_OC3PreloadConfig(TIM8, TIM_OCPreload_Enable); //使能TIM8在CCR2上的預(yù)裝載寄存器

TIM_SetCompare3(TIM8,900);

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

TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;

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

TIM_OC4Init(TIM8, &TIM_OCInitStructure); //根據(jù)T指定的參數(shù)初始化外設(shè)TIM8 OC2

TIM_OC4PreloadConfig(TIM8, TIM_OCPreload_Enable); //使能TIM8在CCR2上的預(yù)裝載寄存器

TIM_SetCompare4(TIM8,1200);

TIM_Cmd(TIM8, ENABLE); //不使能TIM8

TIM_CtrlPWMOutputs(TIM8,ENABLE);

}