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Wait permissions to be set #15

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Wait permissions to be set #15

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19 changes: 19 additions & 0 deletions OPi/sysfs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,33 +2,49 @@
# Copyright (c) 2017 Richard Hull
# See LICENSE.md for details.

import time
import os
from contextlib import contextmanager
from OPi.constants import HIGH, LOW, IN, OUT, \
NONE, RISING, FALLING, BOTH

# Allow to wait up to 1 second for the file have the correct permissions
WAIT_PERMISSION_TIMEOUT = 1.

@contextmanager
def value_descriptor(pin, mode="r"):
path = "/sys/class/gpio/gpio{0}/value".format(pin)
start_time = time.time()
while not os.access(path, os.W_OK) and time.time() - start_time < WAIT_PERMISSION_TIMEOUT:
time.sleep(0.1)
with open(path, mode) as fp:
yield fp


def export(pin):
path = "/sys/class/gpio/export"
start_time = time.time()
while not os.access(path, os.W_OK) and time.time() - start_time < WAIT_PERMISSION_TIMEOUT:
time.sleep(0.1)
with open(path, "w") as fp:
fp.write(str(pin))


def unexport(pin):
path = "/sys/class/gpio/unexport"
start_time = time.time()
while not os.access(path, os.W_OK) and time.time() - start_time < WAIT_PERMISSION_TIMEOUT:
time.sleep(0.1)
with open(path, "w") as fp:
fp.write(str(pin))


def direction(pin, dir):
assert dir in [IN, OUT]
path = "/sys/class/gpio/gpio{0}/direction".format(pin)
start_time = time.time()
while not os.access(path, os.W_OK) and time.time() - start_time < WAIT_PERMISSION_TIMEOUT:
time.sleep(0.1)
with open(path, "w") as fp:
if dir == IN:
fp.write("in")
Expand All @@ -54,6 +70,9 @@ def output(pin, value):
def edge(pin, trigger):
assert trigger in [NONE, RISING, FALLING, BOTH]
path = "/sys/class/gpio/gpio{0}/edge".format(pin)
start_time = time.time()
while not os.access(path, os.W_OK) and time.time() - start_time < WAIT_PERMISSION_TIMEOUT:
time.sleep(0.1)
opts = {
NONE: "none",
RISING: "rising",
Expand Down