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#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0-or-later
# SPDX-FileCopyrightText: 2023 Kent Gibson <warthog618@gmail.com>
"""Minimal example of asynchronously watching for edges on a single line."""
import gpiod
import select
from datetime import timedelta
from gpiod.line import Bias, Edge
def edge_type_str(event):
if event.event_type is event.Type.RISING_EDGE:
return "Rising"
if event.event_type is event.Type.FALLING_EDGE:
return "Falling"
return "Unknown"
def async_watch_line_value(chip_path, line_offset, done_fd):
# Assume a button connecting the pin to ground,
# so pull it up and provide some debounce.
with gpiod.request_lines(
chip_path,
consumer="async-watch-line-value",
config={
line_offset: gpiod.LineSettings(
edge_detection=Edge.BOTH,
bias=Bias.PULL_UP,
debounce_period=timedelta(milliseconds=10),
)
},
) as request:
poll = select.poll()
poll.register(request.fd, select.POLLIN)
# Other fds could be registered with the poll and be handled
# separately using the return value (fd, event) from poll():
poll.register(done_fd, select.POLLIN)
while True:
for fd, _event in poll.poll():
if fd == done_fd:
# perform any cleanup before exiting...
return
# handle any edge events
for event in request.read_edge_events():
print(
"offset: {} type: {:<7} event #{}".format(
event.line_offset, edge_type_str(event), event.line_seqno
)
)
if __name__ == "__main__":
import os
import threading
# run the async executor (select.poll) in a thread to demonstrate a graceful exit.
done_fd = os.eventfd(0)
def bg_thread():
try:
async_watch_line_value("/dev/gpiochip0", 5, done_fd)
except OSError as ex:
print(ex, "\nCustomise the example configuration to suit your situation")
print("background thread exiting...")
t = threading.Thread(target=bg_thread)
t.start()
# Wait for two minutes, unless bg_thread exits earlier, then graceful exit.
t.join(timeout=120)
if t.is_alive():
os.eventfd_write(done_fd, 1)
t.join()
os.close(done_fd)
print("main thread exiting...")
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