def check_state(self):
        """Tracks differences in the device state."""
        if self.dpad:
            x_state, y_state = self.handle_dpad()
        else:
            x_state, y_state = self.handle_abs()

        # pylint: disable=no-member
        new_state = set((
            x_state,
            y_state,
            ('Key', 0x130, int(self.microbit.button_a.is_pressed())),
            ('Key', 0x131, int(self.microbit.button_b.is_pressed())),
            ('Key', 0x13a, int(self.microbit.pin0.is_touched())),
            ('Key', 0x133, int(self.microbit.pin1.is_touched())),
            ('Key', 0x134, int(self.microbit.pin2.is_touched())),
        ))
        events = new_state - self.state
        self.state = new_state
        return events
Tracks differences in the device state.