stm32 定時器 PWM 更改頻率

TIM_Period 溢出計數值，（如有中斷）達到這個值就中斷 arr

TIM_Prescaler 預分頻 psc

調節佔空比 TIMx_SetCompare(1,0-arr); //TIM x爲定時器數字如TIM2、TIM3，參數1位通道，參數2爲ccr 此致時間內與電平翻轉比如默認0-arr都爲高電平，如setcompare的值爲arr/2，就是0-arr/2 爲低電平 arr/2-arr爲高電平佔空比 50%。

時鐘頻率爲 72M

公式：

時鐘頻率(system clk) / 預分頻(psc) /想要的pwm頻率 = arr（重裝值）

例子： 72M / 1 / 2000HZ = 36000

arr和psc在設置的時候都要減一，因爲在硬件上會自動加一，就是 psc = 0 ， arr = 35999

TIM_TimeBaseStructure.TIM_Period = (1000-1); //設置在下一個更新事件裝入活動活動的自動重裝載寄存器週期的值計數到1000爲1ms

TIM_TimeBaseStructure.TIM_Prescaler =(72-1); //設置用來作爲TIMx時鐘頻率除數的預分頻值 1M的計數頻率

arr * psc / 時鐘頻率 = 定時時間

定時時間T = 1000 * 72 / 72000 000 = 1ms

TIM_Prescaler = 72 – 1; t = 72 / 72000 000 = 1us,即TIMx->CNT每1us加一次

TIM_Period = 1000;當TIMx->CNT計數值達到1000us(也就是一開始計算的定時時間1ms),進入中斷服務函數,msHcCount將自動加一

調節頻率：
1.通過更改預分頻器的值，改變計數器的頻率的方式改變PWM波的頻率
在STM32F103中有封裝好的調節預分頻器的函數 TIM_PrescalerConfig()；直接調用即可。

溢出計數值(arr 值域0-65536)=72MHz/想得到的頻率

按照72M的預分頻，頻率（範圍約等於）= 1100HZ - 72MHZ

例子：

volatile uint32 pulse_width = 0;
volatile uint32	direction = 0;

void PWM_Init(u16 arr,u16 psc)
{
	GPIO_InitTypeDef  GPIO_InitStructure;
	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	TIM_OCInitTypeDef TIM_OCInitStructure;
	NVIC_InitTypeDef NVIC_InitStructure;
	
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO | RCC_APB2Periph_GPIOA,ENABLE);

	
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;        
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;                    //IO口複用推輓輸出
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;                  //IO口速度
	GPIO_Init(GPIOA, &GPIO_InitStructure);	//USART輸出IO口
	
	TIM_DeInit(TIM2);
	
	TIM_TimeBaseStructure.TIM_Period = arr; //定時週期
	TIM_TimeBaseStructure.TIM_Prescaler =psc; //預分頻1，36M
	TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //時鐘分頻因子
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //向上計數模式
	TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);
	
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; //輸出PWM模式
	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //使能輸出
	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;//輸出極性
	TIM_OCInitStructure.TIM_Pulse = 50;
	
	TIM_OC1Init(TIM2,&TIM_OCInitStructure);
	TIM_OC2Init(TIM2,&TIM_OCInitStructure);
	TIM_OC3Init(TIM2,&TIM_OCInitStructure);
	TIM_OC4Init(TIM2,&TIM_OCInitStructure);
	
	TIM_OC1PreloadConfig(TIM2,TIM_OCPreload_Enable);
	TIM_OC2PreloadConfig(TIM2,TIM_OCPreload_Enable);
	TIM_OC3PreloadConfig(TIM2,TIM_OCPreload_Enable);
	TIM_OC4PreloadConfig(TIM2,TIM_OCPreload_Enable);

//可以選擇有中斷或無中斷
//	TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE );
//		
//	NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn; 
//	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; 
//	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;  
//	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
//	NVIC_Init(&NVIC_InitStructure);  


	//TIM_ARRPreloadConfig(TIM2,ENABLE);
	TIM_Cmd(TIM2,ENABLE);
}

//可以選擇有中斷或無中斷
void TIM2_IRQHandler(void)
{
	if(TIM_GetITStatus(TIM2,TIM_IT_Update) != RESET)
	{
		TIM_ClearITPendingBit(TIM2,TIM_IT_Update);
		
		if(pulse_width == 0)
			direction = 0;
		else if(pulse_width == 100)
			direction = 1;

		if(direction == 0)
			pulse_width++;
		else
			pulse_width--;
		TIM_SetCompare1(TIM2, pulse_width);
		
	}

}

//頻率 5k,10k,20k,50k,100k
unsigned short fres[5] = {14399,7199,3599,1439,719};

int main()                                                                          
{   

		ledinit();

		PWM_Init(99,7199);

		while(1)
		{

		for(i=0;i<5;i++)
		{
        //這裏的 tim_cmd disable 和 enable 可以不加，沒影響  delay_ms也是
   		TIM_Cmd(TIM2,DISABLE);
        delay_ms(5);
		TIM_PrescalerConfig(TIM2,fres[i],TIM_PSCReloadMode_Immediate);
        TIM_SetCounter(TIM2,0);
		TIM_Cmd(TIM2,ENABLE);
		delay_ms(50);
		}
			
		}
}

2通過普通定時器的中斷去更新gpio的輸出方式改變PWM波的頻率，微調setcount 的值可以平緩過渡頻率
例子：

void ledinit()
{
	GPIO_InitTypeDef GPIO_InitStructure;
	RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB , ENABLE); 						 					 
	GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_12;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; 
	GPIO_Init(GPIOB, &GPIO_InitStructure);
	GPIO_SetBits(GPIOB , GPIO_Pin_12);
	
}

void MY_TIM3_Init(u16 arr,u16 psc){

	NVIC_InitTypeDef NVIC_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;


    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);


    TIM_TimeBaseStructure.TIM_Period = arr;
    TIM_TimeBaseStructure.TIM_Prescaler = psc;


    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //????
    TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);
		
	TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE );
	NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn; 
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;  
	NVIC_Init(&NVIC_InitStructure);  

    TIM_Cmd(TIM3,ENABLE);
}

void TIM3_IRQHandler(void)
{
	if(TIM_GetITStatus(TIM3,TIM_IT_Update) != RESET)
	{
		TIM_ClearITPendingBit(TIM3,TIM_IT_Update);
		ledcount++;
		if(ledcount > setcount)
		{
			ledcount = 0;
			ledstate = ~ledstate;
			if(ledstate > 0)
			{
				GPIO_SetBits(GPIOB , GPIO_Pin_12);
			}
			else
			{
				GPIO_ResetBits(GPIOB , GPIO_Pin_12);
			}
			
			
		}

		
	}
}

volatile uint32 ledcount = 0;
volatile uint32 setcount = 1;

int main()                                                                          
{  
    MY_TIM3_Init(9,7199);
    ledinit();


		while(1)
		{
			setcount++;
			if(setcount > 100)
			{
					setcount = 1;
			}
			delay_ms(100);
        }
}

2通過更改arr值改變PWM波的頻率
例子：

void PWM_Init(u16 arr,u16 psc)
{
	GPIO_InitTypeDef  GPIO_InitStructure;
	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	TIM_OCInitTypeDef TIM_OCInitStructure;
	NVIC_InitTypeDef NVIC_InitStructure;
	
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO | RCC_APB2Periph_GPIOA,ENABLE);

	
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;        
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;                    //IO口複用推輓輸出
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;                  //IO口速度
	GPIO_Init(GPIOA, &GPIO_InitStructure);	//USART輸出IO口
	
	TIM_DeInit(TIM2);
	
	TIM_TimeBaseStructure.TIM_Period = arr; //定時週期
	TIM_TimeBaseStructure.TIM_Prescaler =psc; //預分頻1，36M
	TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //時鐘分頻因子
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //向上計數模式
	TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);
	
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; //輸出PWM模式
	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //使能輸出
	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;//輸出極性
	TIM_OCInitStructure.TIM_Pulse = (int)(arr+1)/2;;
	
	

	
	TIM_OC1Init(TIM2,&TIM_OCInitStructure);
//	TIM_OC2Init(TIM2,&TIM_OCInitStructure);
//	TIM_OC3Init(TIM2,&TIM_OCInitStructure);
//	TIM_OC4Init(TIM2,&TIM_OCInitStructure);
	
	TIM_OC1PreloadConfig(TIM2,TIM_OCPreload_Enable);
//	TIM_OC2PreloadConfig(TIM2,TIM_OCPreload_Enable);
//	TIM_OC3PreloadConfig(TIM2,TIM_OCPreload_Enable);
//	TIM_OC4PreloadConfig(TIM2,TIM_OCPreload_Enable);


//	TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE );
//		
//	NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn; 
//	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; 
//	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;  
//	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
//	NVIC_Init(&NVIC_InitStructure);  


	TIM_ARRPreloadConfig(TIM2,ENABLE);
	TIM_Cmd(TIM2,ENABLE);
}



//PWM_Init(35999,0);				//2k, 4k,   8,    16k,   32k,     64k    144k   480k
unsigned short sfresarr[8] = {35999,17999,8999, 4499,  2249   ,  1124   ,499   ,149 };

int main()
{
	SystemInit();
    PWM_Init(35999,0);
	while(1)
	{
		TIM_Cmd(TIM2,DISABLE);
		TIM_ARRPreloadConfig(TIM2,DISABLE);
		delay_ms(20);
		TIM_SetCompare1(TIM2, sfresarr[i+1]);
		TIM_SetAutoreload(TIM2, sfresarr[7]);
		TIM_ARRPreloadConfig(TIM2,ENABLE);
        TIM_SetCounter(TIM2,0);
		TIM_Cmd(TIM2,ENABLE);
		delay_ms(500);
    }
}

stm32 定時器 PWM 更改頻率

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