参考： STM32的PWM输入模式设置并用DMA接收数据
Input capture mode
The input stage samples the corresponding TIx input to generate a filtered signal TIxF.
Then, an edge detector with polarity selection generates a signal (TIxFPx)
which can be used as trigger input by the slave mode controller or as the capture command.
It is prescaled before the capture register (ICxPS).
In Input capture mode, the Capture/Compare Registers (TIMx_CCRx) are used to latch the value of the counter
after a transition detected by the corresponding ICx signal.
When a capture occurs, the corresponding CCXIF flag (TIMx_SR register) is set and an interrupt
or a DMA request can be sent if they are enabled.
If a capture occurs while the CCxIF flag was already high, then the over-capture flag CCxOF (TIMx_SR register) is set.
CCxIF can be cleared by software by writing it to ‘0’ or by reading the captured data stored in the TIMx_CCRx register.
CCxOF is cleared when you write it to ‘0’.
The following example shows how to capture the counter value in TIMx_CCR1 when TI1 input rises.
To do this, use the following procedure:
Select the active input:
TIMx_CCR1 must be linked to the TI1 input, so write the CC1S bits to 01 in the TIMx_CCMR1 register.
As soon as CC1S becomes different from 00, the channel is configured in input and the TIMx_CCR1 register becomes read-only.
Program the input filter duration you need with respect to the signal you connect to the timer
(by programming ICxF bits in the TIMx_CCMRx register if the input is a TIx input).
Let’s imagine that, when toggling, the input signal is not stable during at must 5 internal clock cycles.
We must program a filter duration longer than these 5 clock cycles.
We can validate a transition on TI1 when 8 consecutive samples with the new level have been detected (sampled at fDTS frequency).
Then write IC1F bits to 0011 in the TIMx_CCMR1 register.
Select the edge of the active transition on the TI1 channel by writing CC1P and CC1NP bits to 0
in the TIMx_CCER register (rising edge in this case).
Program the input prescaler. In our example, we wish the capture to be performed at each valid transition,
so the prescaler is disabled (write IC1PS bits to ‘00’ in the TIMx_CCMR1 register).
Enable capture from the counter into the capture register by setting the CC1E bit in the TIMx_CCER register.
If needed, enable the related interrupt request by setting the CC1IE bit in the TIMx_DIER register,
and/or the DMA request by setting the CC1DE bit in the TIMx_DIER register.
When an input capture occurs:
The TIMx_CCR1 register gets the value of the counter on the active transition.
CC1IF flag is set (interrupt flag). CC1OF is also set if at least two consecutive captures occurred whereas the flag was not cleared.
An interrupt is generated depending on the CC1IE bit.
A DMA request is generated depending on the CC1DE bit.
In order to handle the overcapture, it is recommended to read the data before the overcapture flag.
This is to avoid missing an overcapture which could happen after reading the flag and before reading the data.
Note:
IC interrupt and/or DMA requests can be generated by software by setting the corresponding CCxG bit in the TIMx_EGR register.
STM32输入捕获模式设置并用DMA接收数据
本文博客链接:http://blog.csdn.net/jdh99,作者:jdh
环境：
主机:WIN7
开发环境:MDK4.72
MCU:STM32F103
说明：
项目中需要进行红外学习,于是采用输入捕获取得电平变化时间.并将数据放在DMA中.这样可以避免频繁中断消耗CPU资源.
采用的是PB1脚,对应TIM3的通道4.
/*********************************************************************
* 接口函数:初始化红外学习模块
**********************************************************************/ void inf_infrared_study_init(void)
{
//初始化io口
inf_init_io();
//初始化中断
//inf_init_irq();
//初始化定时器
inf_init_timer(); //打开DMA
inf_infrared_study_open_dma();
//打开定时器
inf_infrared_study_open_timer();
} /*********************************************************************
* 初始化io口
**********************************************************************/ static void inf_init_io(void)
{
//定义IO初始化结构体
GPIO_InitTypeDef GPIO_InitStructure; //初始化时钟
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB,ENABLE);
//管脚初始化
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
//设置为输入
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
//初始化
GPIO_Init(GPIOB, &GPIO_InitStructure);
} /*********************************************************************
* 初始化中断
**********************************************************************/ static void inf_init_irq(void)
{
//定义外部中断结构体
EXTI_InitTypeDef EXTI_InitStructure; //初始化中断脚复用时钟
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);
//配置中断源
GPIO_EXTILineConfig(GPIO_PortSourceGPIOB,GPIO_PinSource1);
// 配置下降沿触发
EXTI_ClearITPendingBit(EXTI_Line1);
EXTI_InitStructure.EXTI_Line = EXTI_Line1;
EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_LineCmd = ENABLE;
EXTI_Init(&EXTI_InitStructure);
} /*********************************************************************
* 初始化定时器
**********************************************************************/ static void inf_init_timer(void)
{
//定义定时器结构体
TIM_TimeBaseInitTypeDef timInitStruct;
//输入捕获结构体
TIM_ICInitTypeDef tim_icinit;
//定义DMA结构体
DMA_InitTypeDef DMA_InitStructure; //启动DMA时钟
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
//DMA1通道3配置
DMA_DeInit(DMA1_Channel3);
//外设地址
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&TIM3->CCR4);
//内存地址
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Rx_Buf_Tim_Dma;
//dma传输方向单向
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
//设置DMA在传输时缓冲区的长度
DMA_InitStructure.DMA_BufferSize = RX_LEN_TIM_DMA;
//设置DMA的外设递增模式，一个外设
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
//设置DMA的内存递增模式
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
//外设数据字长
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
//内存数据字长
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
//设置DMA的传输模式
//DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
//设置DMA的优先级别
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
//设置DMA的2个memory中的变量互相访问
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel3,&DMA_InitStructure); //开启时钟
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
//重新将Timer设置为缺省值
TIM_DeInit(TIM3);
//采用内部时钟给TIM3提供时钟源
TIM_InternalClockConfig(TIM3);
//预分频
timInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
//计数频率为500ns跳转1次
timInitStruct.TIM_Prescaler = SystemCoreClock / - ;
//向上计数
timInitStruct.TIM_CounterMode = TIM_CounterMode_Up;
timInitStruct.TIM_RepetitionCounter = ;
//这个值实际上就是TIMX->ARR，延时开始时重新设定即可
timInitStruct.TIM_Period = 0xffff;
//初始化定时器3
TIM_TimeBaseInit(TIM3, &timInitStruct); //输入捕获配置
//选择通道
tim_icinit.TIM_Channel = TIM_Channel_4;
//硬件滤波
tim_icinit.TIM_ICFilter = 0x0;
//触发捕获的电平
tim_icinit.TIM_ICPolarity = TIM_ICPolarity_Falling;
//每次检测到触发电平都捕获
tim_icinit.TIM_ICPrescaler= TIM_ICPSC_DIV1;
//通道方向选择
tim_icinit.TIM_ICSelection = TIM_ICSelection_DirectTI;
//初始化
TIM_ICInit(TIM3,&tim_icinit); //禁止ARR预装载缓冲器
TIM_ARRPreloadConfig(TIM3, DISABLE); //输入跳变选择
TIM_SelectInputTrigger(TIM3, TIM_TS_TI2FP2);
//从机模式:复位模式
TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset);
//主从模式选择
TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable); //配置定时器的DMA
TIM_DMAConfig(TIM3,TIM_DMABase_CCR4,TIM_DMABurstLength_2Bytes);
//产生DMA请求信号
TIM_DMACmd(TIM3, TIM_DMA_CC4, ENABLE);
//打开定时器
TIM_Cmd(TIM3, ENABLE);
} /*********************************************************************
* 接口函数:打开定时器
*参数:state:状态:0:关闭,1:打开
**********************************************************************/ void inf_infrared_study_open_timer(uint8_t state)
{
if (state)
{
TIM_Cmd(TIM3, ENABLE);
}
else
{
TIM_Cmd(TIM3, DISABLE);
}
} /*********************************************************************
* 接口函数:打开中断
*参数:state:状态:0:关闭,1:打开
**********************************************************************/ void inf_infrared_study_open_irq(uint8_t state)
{
//定义中断结构体
NVIC_InitTypeDef NVIC_InitStructure ; if (state)
{
//打开中断
NVIC_InitStructure.NVIC_IRQChannel = EXTI1_IRQn; //通道设置为外部中断线
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = ; //中断抢占先等级
NVIC_InitStructure.NVIC_IRQChannelSubPriority = ; //中断响应优先级
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //打开中断
NVIC_Init(&NVIC_InitStructure); //初始化
}
else
{
//关闭中断
NVIC_InitStructure.NVIC_IRQChannel = EXTI1_IRQn; //通道设置为外部中断线
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = ; //中断抢占先等级
NVIC_InitStructure.NVIC_IRQChannelSubPriority = ; //中断响应优先级
NVIC_InitStructure.NVIC_IRQChannelCmd = DISABLE; //打开中断
NVIC_Init(&NVIC_InitStructure); //初始化
}
} /*********************************************************************
* 接口函数:打开DMA
*参数:state:状态:0:关闭,1:打开
**********************************************************************/ void inf_infrared_study_open_dma(uint8_t state)
{
if (state)
{
//设置传输数据长度
//DMA_SetCurrDataCounter(DMA1_Channel3,RX_LEN_TIM_DMA);
//打开DMA
DMA_Cmd(DMA1_Channel3,ENABLE);
}
else
{
DMA_Cmd(DMA1_Channel3,DISABLE);
}
} /*********************************************************************
* 接口函数:得到DMA接收帧长
*返回:帧长
**********************************************************************/ uint16_t inf_infrared_study_dma_rx_len(void)
{
//获得接收帧帧长
return (RX_LEN_TIM_DMA - DMA_GetCurrDataCounter(DMA1_Channel3));
}
注意：
除TIM6和TIM7之外的定时器都只能采用上升沿或者下降沿捕捉而不能采用双边沿捕捉.
#define TIM_ICPolarity_Rising ((uint16_t)0x0000)
#define TIM_ICPolarity_Falling ((uint16_t)0x0002)
#define TIM_ICPolarity_BothEdge ((uint16_t)0x000A)
#define IS_TIM_IC_POLARITY(POLARITY) (((POLARITY) == TIM_ICPolarity_Rising) ||
((POLARITY) == TIM_ICPolarity_Falling))
#define IS_TIM_IC_POLARITY_LITE(POLARITY) (((POLARITY) == TIM_ICPolarity_Rising) ||
((POLARITY) == TIM_ICPolarity_Falling)||
((POLARITY) == TIM_ICPolarity_BothEdge))