A Switch object is used to control a push-button switch.

Usage:

sw = pyb.Switch()       # create a switch object
sw()                    # get state (True if pressed, False otherwise)
sw.callback(f)          # register a callback to be called when the
                        #   switch is pressed down
sw.callback(None)       # remove the callback

Example:

pyb.Switch().callback(lambda: pyb.LED(1).toggle())

Create and return a switch object.

.. method:: switch()

   Return the switch state: ``True`` if pressed down, ``False`` otherwise.

.. method:: switch.callback(fun)

   Register the given function to be called when the switch is pressed down.
   If ``fun`` is ``None``, then it disables the callback.