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Created by Franck Albinet with source available here. Also presented by NSRC at APRICOT 2018.

Button: Detecting Pysense board button pressure

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# we import the Pin `class` from machine Pycom modules
from machine import Pin

# then we create a `pin` object
button = Pin("P14", mode=Pin.IN, pull=Pin.PULL_UP)

You notice that to create a Pin object we need to specify three arguments:

1. pin's id "P14" - see Pysense board manual "pysense-pinout-comp.pdf" in /labs/references;
2. pin's mode Pin.IN specifying that this is an input
3. pull method Pin.PULL_UP specifying we want a pull-up resistor. Loosely speaking, a pull-up or pull-down resistor will ensure that the pin is in either a high or low state, while also using a low amount of current and as a result prevents unknown state of the input. You can consult this blog post for further information https://learn.sparkfun.com/tutorials/pull-up-resistors.

Now that we have a button object, let's read repeatedly the state of the input. In our case when not pressed the button's value button() should be 1 and 0 when pressed (pull-up resistor).

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class Button:
    def __init__(self, id):
        self.pressed = False
        self.btn = Pin(id, mode=Pin.IN, pull=Pin.PULL_UP)

__init___ is a special method called at instance/object creation (when we call Button('button_id')actually). We initialize here button's state and create it.

    def on(self):
        self.btn.callback(Pin.IRQ_FALLING | Pin.IRQ_RISING,
                          self._handler)
    def off(self):
        self.btn.callback(Pin.IRQ_FALLING | Pin.IRQ_RISING,
                          None)

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