pwm 捕获

发表于 2017-8-24 14:38

下为numaker bricks的一段程序，我对pwm捕获的一些设置比较疑惑。这个程序是关于HC-SR04，获取高电平时间，我原以为pwm捕获要配置为上升沿和下降沿触发才算ok，没想到它只配置fall-edge，在计算高电平的时间竟然还去明目张胆的获取rising-edge的时间，再去获取fall-edge的时间。想到这里只能认为是上升沿和下降沿的中断无论是否使能与上/下升沿寄存器保存计数器的值毫无关系。唉，多么痛的领悟

// ----------Set PWM0 CH4 as SONAR Rx---------------
/* set PWM1 channel 5 capture configuration, 5us*/
PWM_ConfigCaptureChannel(PWM0, 4, 5000, 0);

/* Enable capture falling edge interrupt for PWM0 channel 3 */
PWM_EnableCaptureInt(PWM0, 4, PWM_CAPTURE_INT_FALLING_LATCH);

/* Enable PWM0 NVIC interrupt */

/*p2对应的应该是pwm的4、5通道，两个通道共享一个INT*/
NVIC_EnableIRQ(PWM0P2_IRQn);

/* Enable Timer for PWM0 channel 4 */
PWM_Start(PWM0, PWM_CH_4_MASK);

/*Enable Input Schmitt Trigger*/
//PC->SMTEN |= GPIO_SMTEN_SMTEN4_Msk;

/* Enable Capture Function for PWM0 channel 4 */
PWM_EnableCapture(PWM0, PWM_CH_4_MASK);

/* Enable falling capture reload */
PWM0->CAPCTL |= PWM_CAPCTL_FCRLDEN4_Msk;

发表于 2017-8-24 14:39

uint16_t IrSonar_CalPeriodTime(PWM_T *PWM, uint32_t u32Ch)//这是计算的函数
{
uint16_t u16RisingTime, u16FallingTime, u16Period;

u16RisingTime = PWM_GET_CAPTURE_RISING_DATA(PWM, u32Ch);

u16FallingTime = PWM_GET_CAPTURE_FALLING_DATA(PWM, u32Ch);

u16Period = u16RisingTime - u16FallingTime;

//printf("\nCapture Result: Rising Time = %d, Falling Time = %d \nHigh Period = %d",
//u16RisingTime, u16FallingTime, u16Period);

return u16Period;

发表于 2017-8-24 16:18

好纠结的经验啊。

[技术问答] pwm 捕获

相关帖子

浏览过的版块