无人机底层驱动+STM32F4学习心得-4.PWM初始化及输入捕获

PWM输出：比较常见应用在控制电机转速，舵机转角、控制某些特定的LED灯

输入捕获计时：实际应用在测量PWM、输入波形的周期与占空比。用于仪表仪器上，检测当前的电平计数等（检测超声波、检测温度等一些特殊的需要计时的传感器）

#include "bsp_PWM.h"
#include <stdbool.h>

//函数功能：初始化定时器1的PWM输出，其中PWM输出端口为PE9、PE11、PE13、PE14;PWM的输出频率为400HZ，精度为10000
bool PWM_Out_Init(void)
{
   GPIO_InitTypeDef GPIO_InitStruct;
   TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
   TIM_OCInitTypeDef TIM_OCInitStruct;

   RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE,ENABLE);

   GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
   GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
   GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_11|GPIO_Pin_13|GPIO_Pin_14;
   GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
   GPIO_InitStruct.GPIO_Speed = GPIO_High_Speed;
   GPIO_Init(GPIOE,&GPIO_InitStruct);

   GPIO_PinAFConfig(GPIOE,GPIO_PinSource9,GPIO_AF_TIM1);
   GPIO_PinAFConfig(GPIOE,GPIO_PinSource11,GPIO_AF_TIM1);
   GPIO_PinAFConfig(GPIOE,GPIO_PinSource13,GPIO_AF_TIM1);
   GPIO_PinAFConfig(GPIOE,GPIO_PinSource14,GPIO_AF_TIM1);

   //输出频率为400HZ，精度为10000
   //计算公式：1/400 = (psc*10000)/时钟周期(84MHZ*2)
   //因为APB2时钟为84Mhz(在时钟源下2分频得到),当APB预分频为1时，
   //定时器时钟频率等于APB的频率，否则，等于APB域的频率的两倍
   uint32_t hz_set =FREQUENCY * acc;
   uint16_t psc = (uint16_t)((84000000 * 2)/hz_set) -1;

   TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
   TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;   //定时器向上计数模式
   TIM_TimeBaseInitStruct.TIM_Period = acc;                                           //预装载值
   TIM_TimeBaseInitStruct.TIM_Prescaler = psc;                                       //预分频系数
   TIM_TimeBaseInit(TIM1,&TIM_TimeBaseInitStruct);

   TIM_OCInitStruct.TIM_OCIdleState = TIM_OCIdleState_Set;       //定时器通道的空闲输出状态
   TIM_OCInitStruct.TIM_OCMode = TIM_OCMode_PWM1;                        //PWM1调制模式
   TIM_OCInitStruct.TIM_OCPolarity = TIM_OCPolarity_High;       //输出极性高
   TIM_OCInitStruct.TIM_OutputState = TIM_OutputState_Enable;//比较输出使能
   TIM_OCInitStruct.TIM_Pulse = 2000;                               //设置占空比 CCRx x = (1,2,3,4)
   TIM_OC1Init(TIM1,&TIM_OCInitStruct);
   TIM_ARRPreloadConfig(TIM1,ENABLE);                               //ARPE使能 (自动装载预装载功能使能[影子寄存器])
   TIM_CtrlPWMOutputs(TIM1,ENABLE);                                   //TIM1主输出使能(高级定时器才需要这一步)
   TIM_OC1PreloadConfig(TIM1,TIM_OCPreload_Enable);   //使能TIM1在CCR1上的预装载寄存器

   TIM_OC2Init(TIM1,&TIM_OCInitStruct);
   TIM_OC2PreloadConfig(TIM1,TIM_OCPreload_Enable);   //使能TIM1在CCR2上的预装载寄存器

   TIM_OC3Init(TIM1,&TIM_OCInitStruct);
   TIM_OC3PreloadConfig(TIM1,TIM_OCPreload_Enable);   //使能TIM1在CCR3上的预装载寄存器

   TIM_OC4Init(TIM1,&TIM_OCInitStruct);
   TIM_OC4PreloadConfig(TIM1,TIM_OCPreload_Enable);   //使能TIM1在CCR4上的预装载寄存器

   TIM_Cmd(TIM1,ENABLE);//定时器1使能

   return true;
}

//函数功能：初始化定时器3的输入捕获，，其输入捕获的引脚为PB0、PB1、PB4、PB5
void TIM_Cap_Init(void)
{
   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
   RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);

   GPIO_InitTypeDef GPIO_InitStruct;
   TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
   TIM_ICInitTypeDef TIM_ICInitStruct;
   NVIC_InitTypeDef NVIC_InitStruct;

   GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
   GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
   GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0|GPIO_Pin_1|GPIO_Pin_4|GPIO_Pin_5;
   GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
   GPIO_InitStruct.GPIO_Speed = GPIO_High_Speed;
   GPIO_Init(GPIOB,&GPIO_InitStruct);

   //端口复用
   GPIO_PinAFConfig(GPIOB,GPIO_PinSource0,GPIO_AF_TIM3);
   GPIO_PinAFConfig(GPIOB,GPIO_PinSource1,GPIO_AF_TIM3);
   GPIO_PinAFConfig(GPIOB,GPIO_PinSource4,GPIO_AF_TIM3);
   GPIO_PinAFConfig(GPIOB,GPIO_PinSource5,GPIO_AF_TIM3);

   //定时器初始化，这里初始化捕获定时器计数频率为1Mhz，也就是1us
   TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
   TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;//向上计数模式
   TIM_TimeBaseInitStruct.TIM_Period = 0xFFFF;
   TIM_TimeBaseInitStruct.TIM_Prescaler = 84-1;
   TIM_TimeBaseInit(TIM3, &TIM_TimeBaseInitStruct);

   //开启捕获中断
   TIM_ITConfig(TIM3,TIM_IT_CC1 | TIM_IT_CC2 | TIM_IT_CC3 | TIM_IT_CC4,ENABLE);

   //设置输入捕获参数
   TIM_ICInitStruct.TIM_Channel = TIM_Channel_1;                               //选择输入端通道1，将IC1映射到TC1上
   TIM_ICInitStruct.TIM_ICFilter = 0xF;                                               //配置滤波器，不滤波
   TIM_ICInitStruct.TIM_ICPolarity = TIM_ICPolarity_BothEdge;   //设置双边沿中断捕获
   TIM_ICInitStruct.TIM_ICPrescaler = TIM_ICPSC_DIV1;                   //配置输入分频，不分频
   TIM_ICInitStruct.TIM_ICSelection = TIM_ICSelection_DirectTI;//映射到TC1
   TIM_ICInit(TIM3,&TIM_ICInitStruct);

   TIM_ICInitStruct.TIM_Channel = TIM_Channel_2;                               //选择输入端通道2，将IC1映射到TC1上
   TIM_ICInitStruct.TIM_ICFilter = 0xF;                                               //配置滤波器，不滤波
   TIM_ICInitStruct.TIM_ICPolarity = TIM_ICPolarity_BothEdge;   //设置双边沿中断捕获
   TIM_ICInitStruct.TIM_ICPrescaler = TIM_ICPSC_DIV1;                   //配置输入分频，不分频
   TIM_ICInitStruct.TIM_ICSelection = TIM_ICSelection_DirectTI;//映射到TC1
   TIM_ICInit(TIM3,&TIM_ICInitStruct);

   TIM_ICInitStruct.TIM_Channel = TIM_Channel_3;                               //选择输入端通道3，将IC1映射到TC1上
   TIM_ICInitStruct.TIM_ICFilter = 0xF;                                               //配置滤波器，不滤波
   TIM_ICInitStruct.TIM_ICPolarity = TIM_ICPolarity_BothEdge;   //设置双边沿中断捕获
   TIM_ICInitStruct.TIM_ICPrescaler = TIM_ICPSC_DIV1;                   //配置输入分频，不分频
   TIM_ICInitStruct.TIM_ICSelection = TIM_ICSelection_DirectTI;//映射到TC1
   TIM_ICInit(TIM3,&TIM_ICInitStruct);

   TIM_ICInitStruct.TIM_Channel = TIM_Channel_4;                               //选择输入端通道4，将IC1映射到TC1上
   TIM_ICInitStruct.TIM_ICFilter = 0xF;                                               //配置滤波器，不滤波
   TIM_ICInitStruct.TIM_ICPolarity = TIM_ICPolarity_BothEdge;   //设置双边沿中断捕获
   TIM_ICInitStruct.TIM_ICPrescaler = TIM_ICPSC_DIV1;                   //配置输入分频，不分频
   TIM_ICInitStruct.TIM_ICSelection = TIM_ICSelection_DirectTI;//映射到TC1
   TIM_ICInit(TIM3,&TIM_ICInitStruct);

   NVIC_InitStruct.NVIC_IRQChannel = TIM3_IRQn;       //配置定时器中断
   NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
   NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
   NVIC_InitStruct.NVIC_IRQChannelSubPriority = 3;
   NVIC_Init(&NVIC_InitStruct);

   TIM_Cmd(TIM3,ENABLE);
}
   uint16_t riseCNT[4];
   uint16_t fallCNT[4];
   uint16_t time[4] = {0};       //高电平的持续时间

void TIM3_IRQHandler()
{

   if(TIM_GetITStatus(TIM3,TIM_IT_CC1) == SET)
   {
       TIM_ClearITPendingBit(TIM3,TIM_IT_CC1);               //清除中断标志位
       if(GPIO_ReadInputDataBit(GPIOB, GPIO_Pin_4))   //通道1读取输入捕获引脚高低电平
       {
           riseCNT[0] = (uint16_t)TIM_GetCounter(TIM3);//获取高电平时定时器的预装载值
       }
       else
       {
           fallCNT[0] = (uint16_t)TIM_GetCounter(TIM3);//获取低电平时定时器的预装载值
           if(riseCNT[0]>fallCNT[0])                                       //周期溢出
           {
               time[0] = 0xFFFF - riseCNT[0] +fallCNT[0] +1;
           }
           else
           {
               time[0] = fallCNT[0] - riseCNT[0];
           }
       }
   }

//该中断服务函数计算的是PWM波高电平的持续时间，定时器1输出PWM的频率为400Hz，即一个周期（上升沿+下降沿）2.5ms，定时器1的预装载值为10000，其CCR1设置为2000，所以其占空比（高电平）为20%，则高电平持续时间为2.5ms * 20% = 500us。

//输入捕获定时器3的预装载值为最大0xFFFF（65535），它的预分频为84M，则计数频率为84/84 = 1Mhz = 1us。所以通过计算PWM波高低电平到达时的预装载值的差，直接可以PWM波的高电平持续时间。
   if(TIM_GetITStatus(TIM3,TIM_IT_CC2) == SET)
   {
       TIM_ClearITPendingBit(TIM3,TIM_IT_CC2);
       if(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_5))   //通道2读取输入捕获引脚高低电平
       {
           riseCNT[1] = (uint16_t)TIM_GetCounter(TIM3);
       }
       else
       {
           fallCNT[1] = (uint16_t)TIM_GetCounter(TIM3);
           if(riseCNT[1]>fallCNT[1])
           {
               time[1] = 0xFFFF - riseCNT[1] + fallCNT[1] + 1;
           }
           else
           {
               time[1] = fallCNT[1] - riseCNT[1];
           }
       }
   }
   if(TIM_GetITStatus(TIM3,TIM_IT_CC3) == SET)
   {
       TIM_ClearITPendingBit(TIM3,TIM_IT_CC3);
       if(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_0))   //通道3读取输入捕获引脚高低电平
       {
           riseCNT[2] = (uint16_t)TIM_GetCounter(TIM3);
       }
       else
       {
           fallCNT[2] = (uint16_t)TIM_GetCounter(TIM3);
           if(riseCNT[2]>fallCNT[2])
           {
               time[2] = 0xFFFF - riseCNT[2] + fallCNT[2] + 1;
           }
           else
           {
               time[2] = fallCNT[2] - riseCNT[2];
           }
       }
   }
   if(TIM_GetITStatus(TIM3,TIM_IT_CC4) == SET)
   {
       TIM_ClearITPendingBit(TIM3,TIM_IT_CC4);
       if(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_1))   //通道4读取输入捕获引脚高低电平
       {
           riseCNT[3] = (uint16_t)TIM_GetCounter(TIM3);
       }
       else
       {
           fallCNT[3] = (uint16_t)TIM_GetCounter(TIM3);
           if(riseCNT[3]>fallCNT[3])
           {
               time[3] = 0xFFFF - riseCNT[3] + fallCNT[3] + 1;
           }
           else
           {
               time[3] = fallCNT[3] - riseCNT[3];
           }
       }

}
}

程序执行结果：将PWM输出四个引脚通道与输入捕获四个引脚通道连接起来，通过调试watch窗口查看数组time的值为500，单位us。

无人机底层驱动+STM32F4学习心得-4.PWM初始化及输入捕获

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