STM32 F207的PWM输入捕获频率和占空比

时间：2018-06-22 12:00:02

关键字： pwm 频率

手机看文章

扫描二维码
随时随地手机看文章

[导读] 最近要做一个项目,需要对外部的PWM信号统计频率和占空比,那做吧使用的是STM32F207的片子看datasheet,发现定时器几大功能之一就是对PWM信号的捕获比较.说明定时器即可以产生PWM信号,还可以对外部的PWM信

最近要做一个项目,需要对外部的PWM信号统计频率和占空比,那做吧

使用的是STM32F207的片子

看datasheet,发现定时器几大功能之一就是对PWM信号的捕获比较.说明定时器即可以产生PWM信号,还可以对外部的PWM信号捕获.

自己仿真一下吧,将D0脚作用PWM信号的输出,用定时器3调整其高低电平输出时间,就算是一路占空比可调的PWM信号了.

将定时器2的CH2作为PWM信号的输入脚,即GPIOA1脚,将D0接到A1脚上.

先配置一下吧

//GPIO配置

RCC_AHBxPeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE); //A口

RCC_AHBxPeriphClockCmd(RCC_AHB1Periph_GPIOD,ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM2);//A0口复用为定时器2

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; //配置为复用脚
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOD, &GPIO_InitStructure);

//两路定时器的配置,这个定时器的配置还是有玄机在里面的,等会再讲

void TIM3_Configuration(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
/* ---------------------------------------------------------------
PCLK1=120/4=30MHz
TIM2 CLK = 30MHz * 2 = 60MHz, Prescaler = 300, TIM3 counter clock = 50,周期就为4K,定时器时间是0.25mS
--------------------------------------------------------------- */
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 50;
TIM_TimeBaseStructure.TIM_Prescaler =(300-1);
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

/*----------------------------------------------------------------
TIM IT enable 使能或者失能指定的TIM中断
TIM3: TIM 中断源
TIM_IT_Update | TIM_IT_Trigger: TIM 触发中断源
----------------------------------------------------------------*/
TIM_ITConfig(TIM3, TIM_IT_Update | TIM_IT_Trigger, ENABLE);

/* TIM3 enable counter 使能TIMx外设*/
TIM_Cmd(TIM3, ENABLE);
}

//这个函数数F2的标准库自带的例子,大家可以自己去研究下
void TIM2_Configuration(void)
{
TIM_ICInitTypeDef TIM_ICInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);

/* Time base configuration */
TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
TIM_ICInitStructure.TIM_ICPolarity =TIM_ICPolarity_Rising;
TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
TIM_ICInitStructure.TIM_ICFilter = 0x0;
TIM_PWMIConfig(TIM2, &TIM_ICInitStructure);

/* Select the TIM2 Input Trigger: TI2FP2 */
TIM_SelectInputTrigger(TIM2, TIM_TS_TI2FP2);

/* Select the slave Mode: Reset Mode */
TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Reset);

/* Enable the Master/Slave Mode */
TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);

/* TIM enable counter */

/* Enable the CC2 Interrupt Request */
TIM_ITConfig(TIM2, TIM_IT_CC2, ENABLE);

TIM_Cmd(TIM2, ENABLE);

}

//中断处理,这里看到用全局变量tim_cnt对一自然数取余,就可以随意调整占空比了,例如tim_cnt累加到4的倍数才拉高,其余全为低电平,那高电平占空比就是1/4=25%

void TIM3_IRQHandler(void)
{
//int i;
if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET) //检查指定的TIM中断发生与否:TIM 中断源
{

if((tim_cnt%4) == 0)
GPIO_SetBits(GPIOD, GPIO_Pin_0);
else
GPIO_ResetBits(GPIOD, GPIO_Pin_0);
tim_cnt++;
TIM_ClearITPendingBit(TIM3, TIM_IT_Update);
}

}

//这个定时器就是计算PWM信号的频率和占空比了
void TIM2_IRQHandler(void)
{
RCC_ClocksTypeDef RCC_Clocks;
RCC_GetClocksFreq(&RCC_Clocks);
/* Clear TIM2 Capture compare interrupt pending bit */
TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);

/* Get the Input Capture value */
IC2Value = TIM_GetCapture2(TIM2);
//printf("IC2Value:%d!!!rn",IC2Value);
if (IC2Value != 0)
{
/* Duty cycle computation */
IC1Value = TIM_GetCapture1(TIM2);
DutyCycle = (IC1Value * 100) / IC2Value;

/* Frequency computation */
Frequency = (RCC_Clocks.HCLK_Frequency) / 2 / IC2Value;
//Frequency = 30000000 / IC2Value;
//printf("clk:%d!!!rn",RCC_Clocks.HCLK_Frequency);
}
else
{
DutyCycle = 0;
Frequency = 0;
}
}