gpio.py 文件源码

def __init__(self, number, direction=INPUT, callback=None, edge=None, active_low=0):
        """
        @type  number: int
        @param number: The pin number
        @type  direction: int
        @param direction: Pin direction, enumerated by C{Direction}
        @type  callback: callable
        @param callback: Method be called when pin changes state
        @type  edge: int
        @param edge: The edge transition that triggers callback,
                     enumerated by C{Edge}
        @type active_low: int
        @param active_low: Indicator of whether this pin uses inverted
                           logic for HIGH-LOW transitions.
        """
        self._number = number
        self._direction = direction
        self._callback = callback
        self._active_low = active_low

        if not os.path.isdir(self._sysfs_gpio_value_path()):
            with open(SYSFS_EXPORT_PATH, 'w') as export:
                export.write('%d' % number)
        else:
            Logger.debug("SysfsGPIO: Pin %d already exported" % number)

        self._fd = open(self._sysfs_gpio_value_path(), 'r+')

        if callback and not edge:
            raise Exception('You must supply a edge to trigger callback on')

        with open(self._sysfs_gpio_direction_path(), 'w') as fsdir:
            fsdir.write(direction)

        if edge:
            with open(self._sysfs_gpio_edge_path(), 'w') as fsedge:
                fsedge.write(edge)
                self._poll = select.epoll()
                self._poll.register(self, (select.EPOLLPRI | select.EPOLLET))
                self.thread = Thread(target=self._run)
                self.thread.daemon = True
                self._running = True
                self.start()

        if active_low:
            if active_low not in ACTIVE_LOW_MODES:
                raise Exception('You must supply a value for active_low which is either 0 or 1.')
            with open(self._sysfs_gpio_active_low_path(), 'w') as fsactive_low:
                fsactive_low.write(str(active_low))