Any idea to use add_event_detect's callback func with args?

[mannok]

Do anyone come up with an idea to let me pass parameter to call back function in add_event_detect'?
something like GPIO.add_event_detect(23, GPIO.RISING , callback=ssEchoHandler, args=(arg1,))
Thanks!!!

[DougieLawson]

Docs for RPi.GPIO's add_event_detect() function are here: http://sourceforge.net/p/raspberry-gpio ... ki/Inputs/

[scotty101]

The documentation doesn't answer the OPs question.

I suspect you'd have to use lamba function to add arguments to the callback. The below code won't work but it might get you somewhere.

Code: Select all

cb = lambda arg1=valueToPass: functionToCall(arg1)
GPIO.add_event_callback(channel, cb, bouncetime=200)

[mannok]

The documentation doesn't answer the OPs question.

I suspect you'd have to use lamba function to add arguments to the callback. The below code won't work but it might get you somewhere.

Code: Select all

cb = lambda arg1=valueToPass: functionToCall(arg1)
GPIO.add_event_callback(channel, cb, bouncetime=200)

This is the answer! Thanks!!!

[elParaguayo]

Does that work?

I thought the add_event_callback passed the channel as the first argument so, if you're using a lambda and don't care about the channel, you'd need to do

Code: Select all

cb = lambda channel, arg1=valueToPass: functionToCall(arg1)
GPIO.add_event_callback(channel, cb, bouncetime=200)

Compare:

Code: Select all

   a = lambda x=2: type(x)
   a("Hello")
=> <type 'str'>
   a = lambda ignore_this, x=2: type(x)
   a("Hello")
=> <type 'int'>

If, however, you just want the channel then you don't need the lambda. Your callback function would just be:

Code: Select all

def cb(channel):
    etc.

[mannok]

Does that work?

I thought the add_event_callback passed the channel as the first argument so, if you're using a lambda and don't care about the channel, you'd need to do

Code: Select all

cb = lambda channel, arg1=valueToPass: functionToCall(arg1)
GPIO.add_event_callback(channel, cb, bouncetime=200)

Compare:

Code: Select all

   a = lambda x=2: type(x)
   a("Hello")
=> <type 'str'>
   a = lambda ignore_this, x=2: type(x)
   a("Hello")
=> <type 'int'>

If, however, you just want the channel then you don't need the lambda. Your callback function would just be:

Code: Select all

def cb(channel):
    etc.

I get this error:
TypeError: <lambda>() takes exactly 2 arguments (1 given)

[elParaguayo]

What does your lambda function look like?

[mannok]

What does your lambda function look like?

callback=lambda echoPin, startTime: func(echoPin, startTime)

[elParaguayo]

What does your lambda function look like?

callback=lambda echoPin, startTime: func(echoPin, startTime)

That's not going to work. If you want to pass the echoPin and startTime then I think you'll need to do this:

Code: Select all

callback=lambda channel, ep=echoPin, st=startTime: func(sp, st)

Please note, my understanding is that ep and st will be set with the value of startTime when the callback is set, not when it is triggered.

[elParaguayo]

Looking at your other post, you have this:

Code: Select all

callback=lambda echoPin: print("Distance", round((time.time()-startEchoTime)*17150), "cm"))

That looks ok to me.

[DougieLawson]

Looking at your other post, you have this:

Code: Select all

callback=lambda echoPin: print("Distance", round((time.time()-startEchoTime)*17150), "cm"))

That looks ok to me.

It looks way too complex when compared to the somewhat simpler code at https://www.dropbox.com/s/cir2860vdkipv ... _sensor.py

[elParaguayo]

Looking at your other post, you have this:

Code: Select all

callback=lambda echoPin: print("Distance", round((time.time()-startEchoTime)*17150), "cm"))

That looks ok to me.

It looks way too complex when compared to the somewhat simpler code at https://www.dropbox.com/s/cir2860vdkipv ... _sensor.py

Can't see the link, but you're right, if the only parameter being passed is echoPin then there's no need for a lambda at all here.

[davecollinsjr]

This worked well for me, where bookshelf is an instance of a class maintaining state, and handle_book_pull is the handler/callback that needs the channel and the bookshelf instance:

Code: Select all

callback = lambda channel, bookshelf=bookshelf: handle_book_pull(channel, bookshelf)
GPIO.add_event_detect(BOOK, GPIO.BOTH, callback, bouncetime=200)