无法添加边缘检测 - Raspberry Pi 3 GPIO

Question

I am using a Raspberry Pi 3 model B.

I tried different approaches using both gpiozero and RPi.GPIO . The problem occurs regardless of the library used.

Here is an example of code that fails with gpiozero .

from gpiozero import Button
from signal import pause

def handle():
    print("Pressed!")

button = None
while not button:
    try:
        button = Button(4, pull_up=True)
        button.when_pressed = handle
    except RuntimeError as e:
        print(e)
        pass

pause()

The line button = Button(4, pull_up=True) always raises a RuntimeError and the output of the program (running python3 ) is:

Failed to add edge detection
Failed to add edge detection
Failed to add edge detection
Failed to add edge detection
# ... it goes on for ages

I already tried to reinstall RPi.GPIO and gpiozero but it did not help.

Here is the full traceback of the exception

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/gpiozero/input_devices.py", line 84, in __init__
    self.pin.when_changed = self._fire_events
  File "/usr/lib/python3/dist-packages/gpiozero/pins/__init__.py", line 240, in <lambda>
    lambda self, value: self._set_when_changed(value),
  File "/usr/lib/python3/dist-packages/gpiozero/pins/rpigpio.py", line 233, in _set_when_changed
    bouncetime=self._bounce)
RuntimeError: Failed to add edge detection

Answer 1

I also get the same problem on raspberry pi3 B with Arch_arm operating system. It seems that this problem have nothing to do with your python code.

---

In Raspberrypi/linux system, You can only use the GPIO with root authority by default.

The /dev/gpiomem instead of /dev/mem , can let user use GPIO with rootless. Of course you should make some changes.

1. add new group name gpio && add your user account name to the group

   sudo group -r gpio sudo usermod -a -G gpio pi

2. add udev rules to /etc/udev/rules.d/

    ls -l /etc/udev/rules.d -rw-r--r-- 1 root root 580 Aug 5 15:02 raspberrypi.rules

   You can add these rules below to the tail of the file raspberrypi.rules with sudo.

    SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio", MODE="0660" SUBSYSTEM=="gpio", KERNEL=="gpiochip*", ACTION=="add", PROGRAM="/bin/sh -c 'chown root:gpio /sys/class/gpio/export /sys/class/gpio/unexport ; chmod 220 /sys/class/gpio/export /sys/class/gpio/unexport'" SUBSYSTEM=="gpio", KERNEL=="gpio*", ACTION=="add", PROGRAM="/bin/sh -c 'chown root:gpio /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value ; chmod 660 /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value'"

Happy coding.

Answer 2

running it with sudo should work

For example

sudo python test-gpio.py