python libgpiod - GPIOD - Event Callback

• gpiod

• ZYW

  ZHI YONG WOO

  8/27/24, 9:58 PM

  Hi,

  Does anyone able to share how to write a callback event on falling edge on an Input GPIO. I can't find any example on how the lib handle event instead of using pulling method to find falling event.

  Please helps.

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• HH

  Harry Huang Staff member

  9/6/24, 3:04 PM

  Hello, you can refer to the following sample.

  #!/usr/bin/env python
  
  #
  import gpiod
  import time
  
  # Define the chip and lines
  chipname = "gpiochip0"  #Please use gpiochip0 if using Raspberry pi 4/3 hardware
  # chipname = "gpiochip4"  #Please use gpiochip4 if using Raspberry pi 5 hardware
  
  line_offset = 6
  
  # Open the GPIO chip
  chip = gpiod.Chip(chipname)
  
  # Get the input line
  line = chip.get_line(line_offset)
  line.request(consumer="my_program", type=gpiod.LINE_REQ_EV_BOTH_EDGES)
  
  def print_event(event):
      if event.type == gpiod.LineEvent.RISING_EDGE:
          print("---AC Power Loss OR Power Adapter Failure---")
          print("Shutdown in 5 seconds")
          time.sleep(5)
      elif event.type == gpiod.LineEvent.FALLING_EDGE:
          print("---AC Power OK, Power Adapter OK---")
  
  try:
      # Wait for events indefinitely
      while True:
          event = line.event_wait()        
          if event:            
              event = line.event_read()
              print_event(event)
  except KeyboardInterrupt:
      print("Exiting...")
  finally:
      chip.close()
  

   

   

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