Multiple GPIO.add_event_detect, one callback function

Question

I have several lever switches that represent scores. I want a single callback function when pressed that acts on the value of that lever. I have this working except it seems to call the function twice. This stops happening if I remove the second add_event_detect for the other channel

GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.setup(27, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

def buttonPressed(value):
    print('Scored! %s'%value)
    print(time.time())

GPIO.add_event_detect(17, GPIO.FALLING, callback=lambda x: buttonPressed(50), bouncetime=2000)
GPIO.add_event_detect(27, GPIO.FALLING, callback=lambda x: buttonPressed(150), bouncetime=2000)

When I push the switch once on channel 17 I get outputted:

 Scored! 50
 1374739135.76
  Scored! 50
 1374739135.76

Note the extra space on the third line, not sure if that has any importance to the issue.

How can I make sure it only gets called once when the lever is pressed and why is adding the second add_event_detect causing the callback function to be fired?

Answer 1

I have had no idea what that lamda is supposed to do, but this is what I would use:

GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.setup(27, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

def buttonPressed(channel):
    if channel==17:
        value=50
    elif channel==27:
        value=150
    print('Scored! %s'%value)
    print(time.time())

GPIO.add_event_detect(17, GPIO.FALLING, callback=buttonPressed, bouncetime=2000)
GPIO.add_event_detect(27, GPIO.FALLING, callback=buttonPressed, bouncetime=2000)