Raspberry Pi-4B，C语言，bcm2835 lib，输入异步上升沿模式下的GPIO引脚可同时检测上升沿和下降沿

Question

嗨，我正在使用Raspberry Pi-4B。 我使用带有bcm2835 lib的C语言，将GPIO引脚编程为输入。 我尝试了GPIO引脚P1-11。它被编程为输入以检测异步上升沿。但是在执行期间，GPESD位在上升沿和下降沿均置1。知道为什么要检测到下降沿吗？

请在下面找到代码并输出：

#include <bcm2835.h>
#include <stdio.h>
 
#define PIN RPI_GPIO_P1_11
 
int main(int argc, char **argv)
{
    //bcm2835_set_debug(1);
 
    if (!bcm2835_init())
        return 1;
 
    // Set RPI pin P1-15 to be an input
    bcm2835_gpio_fsel(PIN, BCM2835_GPIO_FSEL_INPT);
    //  with a pullup
    bcm2835_gpio_set_pud(PIN, BCM2835_GPIO_PUD_DOWN);
    // And a rising edge detect enable
    bcm2835_gpio_aren(PIN);
    bcm2835_gpio_clr_ren(PIN);
    bcm2835_gpio_clr_len(PIN);
    bcm2835_gpio_clr_hen(PIN);
    bcm2835_gpio_clr_fen(PIN);
    bcm2835_gpio_clr_afen(PIN);

    delay(500);
 
    printf("gpio_event: \n");

    while (1)
    {
      uint8_t value = bcm2835_gpio_lev(PIN);
      printf("read from pin %0d: %d\n", PIN, value);

      delay(50);
      if (bcm2835_gpio_eds(PIN))
      {
         delay(50);
         printf("rising edge detected on pin %0d\n",PIN);
         //clear the eds flag by setting it to 1
         bcm2835_gpio_set_eds(PIN);
      }

      // wait a bit
      delay(1000);
    }
 
    bcm2835_close();
    return 0;
}
// Output:
//================================================
//gpio_event: 
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 1
//rising edge detected on pin 17
//read from pin 17: 1
//read from pin 17: 1
//read from pin 17: 1
//read from pin 17: 0
//rising edge detected on pin 17
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 0
//read from pin 17: 0
//================================================