uhd/mpm/python/usrp_mpm/sys_utils/gpio.py

#
# Copyright 2020 Ettus Research, a National Instruments Brand
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
"""
Access to GPIOs via libgpiod
"""

import contextlib
import gpiod


@contextlib.contextmanager
def request_gpio(line, direction):
    """
    Context manager for a GPIO line
    """
    line.request(consumer='mpm', type=direction)
    try:
        yield line
    finally:
        line.release()


class Gpio:
    """
    Class for accessing a named GPIO line via libgpiod
    """

    INPUT = gpiod.LINE_REQ_DIR_IN
    OUTPUT = gpiod.LINE_REQ_DIR_OUT
    FALLING_EDGE = gpiod.LINE_REQ_EV_FALLING_EDGE

    def __init__(self, name, direction=INPUT, default_val=None):
        self._direction = direction
        self._line = gpiod.find_line(name)
        self._out_value = False
        if self._line is None:
            raise RuntimeError('failed to find gpio with name %s' % name)

        if default_val is not None and direction == Gpio.OUTPUT:
            self.set(default_val)

    def get(self):
        """
        Read the value of this GPIO
        """
        if self._direction == self.OUTPUT:
            return self._out_value

        with request_gpio(self._line, self._direction) as gpio:
            return bool(gpio.get_value())

    def set(self, value):
        """
        Set the value of this GPIO
        """
        with request_gpio(self._line, self._direction) as gpio:
            gpio.set_value(int(value))
            self._out_value = bool(value)

    def event_wait(self):
        """
        Wait for an event to happen on this line
        """
        with request_gpio(self._line, self._direction) as gpio:
            while True:
                if gpio.event_wait(sec=1):
                    return True