Parts Swich (or PushButton?) without polling task

[s-celles]

Hello,

In a project, we are using push button and Pingo.

Unfortunately Swich class only provides a class with a polling mechanism.

What is your opinion about adding to Switch class some methods that could be used in a non threading context ?

We could have for example attributes such as pressed or released which would return True or False.

I also noticed that it's odd to have such a class named Switch in a file named button.py

CC @lwalter86

I also wonder how this could behave if passed pin at init could come from a GhostBoard.

For unit test, it will be very convenient to add also methods to simulate that a button is being pressed or released.

but.press()
do_something()
but.release()

Kind regards

[s-celles]

I noticed in https://github.com/pingo-io/pingo-py/blob/master/pingo/parts/test/test_switch.py

class FakeDigitalPin(object):
    def __init__(self):
        self.mode = 'IN'
        self.state = 'LOW'

Maybe this class shouldn't be there (in a test) but should be merged with DigitalPin
https://github.com/pingo-io/pingo-py/blob/master/pingo/board.py

[s-celles]

When but is initialized with a pin (a DigitalPin) from a GhostBoard, press and release method should change internal state of this pin but when but is initialized with a pin (a DigitalPin) from a "real" board it should raise an exception.

[s-celles]

Here is a possible implementation

import pingo
import time

class PushButton(object):
    """A single Push button"""
    def __init__(self, pin, pressed_state=pingo.LOW):
        """Set pressed_state to pingo.LOW when button is pressed
        :param pin: A instance of DigitalPin
        :param pressed_state: use pingo.LOW for pull-up, pingo.HIGH for pull-down
        """
        pin.mode = pingo.IN
        self.pin = pin
        self._pressed_state = pressed_state
        d = {
            pingo.LOW: pingo.HIGH,
            pingo.HIGH: pingo.LOW,
        }
        self._released_state = d[pressed_state]

    def _test_pin_instance(self):
        if not isinstance(self.pin.board, pingo.ghost.ghost.GhostBoard):
            raise(NotImplementedError('pin from a GhostBoard is required'))
        elif not isinstance(self.pin, pingo.board.DigitalPin):
            raise(NotImplementedError('DigitalPin is required'))                

    def press(self):
        self._test_pin_instance()
        board = self.pin.board
        pin = self.pin
        board._set_pin_state(pin, self._pressed_state)

    def release(self):
        self._test_pin_instance()
        board = self.pin.board
        pin = self.pin
        board._set_pin_state(pin, self._released_state)

    @property
    def pressed(self):
        return True if self.pin.state == self._pressed_state else False

    @property
    def released(self):
        return True if self.pin.state == self._released_state else False

[s-celles]

It may be worth to have a look at https://github.com/RPi-Distro/python-gpiozero/blob/master/gpiozero/input_devices.py#L387

[Vido]

Hallo @scls19fr ,

I guess I don't get it. Do you need a 'mock-up' Button-object for testing?

Let me list the features you proposed:

• methods press(self) and release(self), properties pressed(self) and released(self)
• This class will be enable to switch on and off a DigitalPin

So it would behave like a virtual Button, which can set a state via software.

There is something that's not clear:
On the example you posted, pin.mode is set to pingo.IN. In fact, you should not (or perhaps, can not) change a state when pingo.IN is set (when working with a real hardware).

Given you are using GhostBoard, I believe what you are looking for is a way to simulate a "input device". Am I right?

The Question: What is the main purpose of this feature?
(testing, using GhostBoard or Something else?)

---

About FakeDigitalPin, it is used for testing. It is not exposed on the API.

[s-celles]

The goal of such a virtual part is to run unit tests for a app with a virtual push button.
I use it in https://github.com/RaspberryPi-Samples/py-my-key see https://github.com/RaspberryPi-Samples/py-my-key/blob/master/tests/test_py_my_key.py

you can see

my_app.hw.black_btn.press()
...
my_app.hw.black_btn.release()

and in https://github.com/RaspberryPi-Samples/py-my-key/blob/master/py_my_key/cli_rpi_access.py#L97

you can also see

if self.hw.black_btn.pressed and self.hw.red_btn.released:
    ...