STM32 定時器(二)——定時器產生不同頻率的PWM

（1）使能定時器時鐘：RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

（2）定義相應的GPIO：

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2|GPIO_Pin_3|GPIO_Pin_4|GPIO_Pin_5|GPIO_Pin_6;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; //下拉接地，檢測輸入的高電平
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //50M時鐘速度
GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //50M時鐘速度
GPIO_Init(GPIOA, &GPIO_InitStructure);

（3）如果是產生PWM（頻率不變，占空比可變），記得打開PWM控制，在TIM_Configuration()中。

TIM_Cmd(TIM3,ENABLE);

TIM_CtrlPWMOutputs(TIM1,ENABLE);

利用定時器產生不同頻率的PWM

有時候，需要產生不同頻率的PWM，這個時候，設置與產生相同PWM的程序，有關鍵的不一樣。

（一）設置的原理

利用改變定時器輸出比較通道的捕獲值，當輸出通道捕獲值產生中斷時，在中斷中將捕獲值改變，這時，輸出的I/O會產生一個電平翻轉，利用這種辦法，實現不同頻率的PWM輸出。

（二）關鍵設置

在定時器設置中：TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Disable);

在中斷函數中： if (TIM_GetITStatus(TIM3, TIM_IT_CC2) != RESET)
{
TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);
capture = TIM_GetCapture2(TIM3);
TIM_SetCompare2(TIM3, capture + Key_Value);
}

一個定時器四個通道，分別產生不同頻率（這個例子網上也有）

vu16 CCR1_Val = 32768;
vu16 CCR2_Val = 16384;
vu16 CCR3_Val = 8192;
vu16 CCR4_Val = 4096;

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

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

TIM_TimeBaseStructure.TIM_Period = 65535;
TIM_TimeBaseStructure.TIM_Prescaler = 2;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseInit(TIM2, &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;//反向通道無效
TIM_OCInitStructure.TIM_Pulse = CCR1_Val; //占空時間
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //輸出極性
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High; //互補端的極性
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;

TIM_OC1Init(TIM2,&TIM_OCInitStructure); //通道1
TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Disable);

TIM_OCInitStructure.TIM_Pulse = CCR2_Val; //占空時間
TIM_OC2Init(TIM2,&TIM_OCInitStructure); //通道2
TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Disable);

TIM_OCInitStructure.TIM_Pulse = CCR3_Val; //占空時間
TIM_OC3Init(TIM2,&TIM_OCInitStructure); //通道3
TIM_OC3PreloadConfig(TIM2, TIM_OCPreload_Disable);

TIM_OCInitStructure.TIM_Pulse = CCR4_Val; //占空時間
TIM_OC4Init(TIM2,&TIM_OCInitStructure); //通道4
TIM_OC4PreloadConfig(TIM2, TIM_OCPreload_Disable);

TIM_Cmd(TIM2,ENABLE);


//TIM_CtrlPWMOutputs(TIM2,ENABLE);

TIM_ITConfig(TIM2, TIM_IT_CC1 | TIM_IT_CC2 | TIM_IT_CC3 | TIM_IT_CC4, ENABLE);

}

void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2|GPIO_Pin_3|GPIO_Pin_4|GPIO_Pin_5|GPIO_Pin_6|GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_OD; //開漏輸出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //50M時鐘速度
GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0|GPIO_Pin_1;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_OD; //開漏輸出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //50M時鐘速度
GPIO_Init(GPIOB, &GPIO_InitStructure);


GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0|GPIO_Pin_1;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; //上拉輸入
GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; //上拉輸入
GPIO_Init(GPIOC, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; //上拉輸入
GPIO_Init(GPIOB, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);
}

void NVIC_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);

NVIC_InitStructure.NVIC_IRQChannel=TIM2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority=1;
NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
NVIC_Init(&NVIC_InitStructure);
}