记录下输入捕获初始化代码
#define TIM2_ARR 5000
#define TIM2_PSC 72
#define TIM_PSC_CLK (72000000/TIM2_PSC) //定时器计数时钟
void TIM_CaptureInit(u16 arr, u16 psc)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
TIM_ICInitTypeDef TIM2_ICInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); //使能PB,PE端口时钟
GPIO_Config();
TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值
TIM_TimeBaseStructure.TIM_Prescaler = psc; //设置用来作为TIMx时钟频率除数的预分频值 不分频
TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM向上计数模式
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
//初始化TIM2通道3為输入捕获PWM
TIM2_ICInitStructure.TIM_Channel = TIM_Channel_3; // 通道3輸入捕獲PWM选择输入端 IC3映射到TI3上
TIM2_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising; //上升沿捕获
TIM2_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; //映射到TI3上
TIM2_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1; //配置输入分频,不分频
TIM2_ICInitStructure.TIM_ICFilter = 0x00; //IC1F=0000 配置输入滤波器 不滤波
TIM_ICInit(TIM2, &TIM2_ICInitStructure);
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn; //TIM2中断
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道被使能
NVIC_Init(&NVIC_InitStructure); //根据NVIC_InitStruct中指定的参数初始化外设NVIC寄存器
TIM_ClearFlag(TIM2, TIM_IT_Update | TIM_IT_CC3); //清除中斷標誌位
TIM_ITConfig(TIM2, TIM_IT_Update | TIM_IT_CC3, ENABLE); //允许更新中断 ,允许CC3IE捕获中断
TIM_Cmd(TIM2,ENABLE); //使能定时器2
}
//初始化调用
TIM_CaptureInit(TIM2_ARR, TIM2_PSC-1)
相应的定时器输入捕获的引脚初始化：
void GPIO_Config()
{
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); //打开时钟
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2; //PA2为TIM2_CH3
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; //输入浮空模式
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_ResetBits(GPIOA, GPIO_Pin_2);
}
在定时器中断中进行捕获：
void TIM2_IRQHandler(void)
{
if(TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET) //更新中断
{
g_ldCaptureStructure.captureUpatePeriod++; /
TIM_ClearITPendingBit(TIM2, TIM_IT_Update); //清除中断标志位
}
if(TIM_GetITStatus(TIM2, TIM_IT_CC3) != RESET) //通道3发生捕获中断
{
if(g_ldCaptureStructure.captureStartFlag == 0) //还未开始,第一次捕获上升沿
{
g_ldCaptureStructure.captureFinishFlag = 0;
g_ldCaptureStructure.captureRegVal = 0;
g_ldCaptureStructure.captureUpatePeriod = 0;
g_ldCaptureStructure.captureStartFlag = 1; //标志捕获开始
TIM_SetCounter(TIM2, 0); //清零TIM2的计数器
TIM_OC3PolarityConfig(TIM2, TIM_ICPolarity_Falling); //CC1P=1 设置为下降沿捕获
}
else
{
TIM_Cmd(TIM2, DISABLE); //使能定时器2
g_ldCaptureStructure.captureRegVal = TIM_GetCapture3(TIM2);
g_ldCaptureStructure.captureStartFlag = 0;
g_ldCaptureStructure.captureFinishFlag = 1; //標誌捕獲完成
CalcPulseWidth(&g_ldCaptureStructure);
TIM_OC3PolarityConfig(TIM2, TIM_ICPolarity_Rising); //CC1P=0 设置为上升沿捕获
TIM_Cmd(TIM2, ENABLE);
}
TIM_ClearITPendingBit(TIM2, TIM_IT_CC3); //清除中断标志位
}
}
使用到更新中断捕获是因为当输入信号脉宽很大时，捕获寄存器的值可能会溢出，使用更新中断记录溢出次数后就可以计算多大脉宽都没问题。
void CalcPulseWidth(stUserTimCaptureStructure *userCaptureStru)
{
u32 pulseWidthValue = 0;
u16 ledDutyVal;
u16 laserDutyVal;
double signalDuty;
if(userCaptureStru->captureFinishFlag) //捕獲完成
{
pulseWidthValue = ((userCaptureStru->captureRegVal+1)
+ userCaptureStru->captureUpatePeriod * (TIM2_ARR+1));
//计算出占空比 1.0/TIM_PSC_CLK 是定时器时钟周期
//10000是外部信号的频率
signalDuty = (double)pulseWidthValue*(1.0/TIM_PSC_CLK) * 10000;
printf("signalDuty = %2.2f\r\n", signalDuty);
ledDutyVal = signalDuty * 3600;
TIM_SetCompare1(TIM1, ledDutyVal ); //以同样的占空比控制其他LED
laserDutyVal = signalDuty * TIM2_ARR;
TIM_SetCompare4(TIM2, laserDutyVal); //以同样的占空比控制其他LED
}
}
问题记录
原来自己计算的脉宽值：
pulseWidthValue = (userCaptureStru->captureRegVal
+ userCaptureStru->captureUpatePeriod * TIM2_ARR);
昨儿计算脉宽时很挺正常的。今天将输入捕获的PWM频率改成10KHZ，一旦占空比调大到70以上后就会出现计算的占空比不准的问题。
大意，经过一番查找发现问题所在：
https://www.firebbs.cn/thread-14334-1-1.html
将计算脉宽值的式子改成：
pulseWidthValue = ((userCaptureStru->captureRegVal+1)
+ userCaptureStru->captureUpatePeriod * (TIM2_ARR+1));
此后，调大信号发生器PWM信号的占空比，通过查看计算出来的占空比和信号发生器产生的PWM信号的占空比对比也是一致的。