CODEWITHSUNDEEP
pythonraspberry-pigpio
Buddyshot
Buddyshot

Reputation: 1684

Failed to add edge detection - Raspberry Pi 3 GPIO

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

Upvotes: 2

Views: 9096

Answers (2)

Vi.Ci
Vi.Ci

Reputation: 5125

I also get the same problem on Raspberry Pi 3 B with Arch_arm operating system.
It seems that this problem has 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 groupadd -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.

Upvotes: 3

Mouse
Mouse

Reputation: 141

running it with sudo should work

For example

sudo python test-gpio.py

Upvotes: 0

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