Learning ExtInt interrupts

[synimak]

I'm trying to learn how to use interrupts but but getting no where. Everything I do results in the callback being initiated when the pyboard boots and nothing happening when the pin does actually go low. I had some more complex code that I started with but now I'm just trying to just print "Hello" when a pin goes low.

Code: Select all

from pyb import Pin, ExtInt

def call():
	print("Hello")
	
extint = ExtInt(Pin('X1'), ExtInt.IRQ_FALLING, Pin.PULL_UP, call())

while True:
	pass
	
	

What am I missing?

[marfis]

check out the doc:
https://micropython.org/doc/module/pyb/ExtInt

you'll notice that your callback must provide one argument. And in the setup function you have to remove the "()" from call.

[dhylands]

What @marfis said.

By passing call() you're calling the function call once, and passing None (the return value from calling call) to ExtInt which tells it to disable ExtInt handling.

The one call you're seeing is the call that you're making by adding the parenthesis (i.e. call() actually calls the function).

[SpotlightKid]

When you pass a callback function as an argument to another function, you have to pass the function object and not the return value of calling the function. I.e. you don't put () behind the function name, because that means calling the function. You just put the function name as the argument. In Python almost everything is an object, including functions, so when you define a function, you are basically just creating a variable with the function name, which holds a reference to the function object.