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#! /usr/bin/env python
#
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# gpio_trigger.py - execute a command when a GPIO input pin changes
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#
# Version 1.0, latest version, documentation and bugtracker available at:
# https://gitlab.lindenaar.net/scripts/raspberrypi
#
# Copyright (c) 2019 Frederik Lindenaar
#
# This script is free software: you can redistribute and/or modify it under the
# terms of version 3 of the GNU General Public License as published by the Free
# Software Foundation, or (at your option) any later version of the license.
#
# This script is distributed in the hope that it will be useful but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# this program. If not, visit <http://www.gnu.org/licenses/> to download it.
#
from os import fork, system
from argparse import ArgumentParser
from RPi import GPIO
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parser = ArgumentParser(
description='Run command when a Raspberry Pi pin changes to high or low.',
epilog='(*) use \'--\' to stop argument parsing, arguments can contain the '
'following variables: %PIN%=pin number, %STATE%=value (HIGH or LOW)')
parser.add_argument('-D', '--daemon', action='store_true',
help='run in background (as daemon)')
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pgroup = parser.add_mutually_exclusive_group(required=False)
pgroup.add_argument('-P', '--pcb', action='store_const', dest='mode',
const=GPIO.BOARD, default=GPIO.BOARD,
help='GPIO header/board (PCB) pin numbers (default)')
pgroup.add_argument('-S', '--bcm', help='GPIO BCM mode (Broadcom SOC pins)',
action='store_const', dest='mode', const=GPIO.BCM)
parser.add_argument('-p', '--pin', type=int, required=False, default=40,
help='GPIO pin number to use (default: 40)')
pgroup = parser.add_mutually_exclusive_group(required=False)
pgroup.add_argument('-u', '--pull-up', action='store_const', dest='pull',
default=GPIO.PUD_UP, const=GPIO.PUD_UP,
help='internally pull pin up (default)')
pgroup.add_argument('-d', '--pull-down', action='store_const', dest='pull',
const=GPIO.PUD_DOWN, help='internally pull pin down')
pgroup.add_argument('-n', '--no-pull', action='store_const', const=GPIO.PUD_OFF,
dest='pull', help='don\'t pull pin up or down internally')
pgroup = parser.add_mutually_exclusive_group(required=False)
pgroup.add_argument('-f', '--edge-falling', action='store_const',
const=GPIO.FALLING, dest='edge', default=GPIO.FALLING,
help='respond to pin going down (default)')
pgroup.add_argument('-r', '--edge-rising', action='store_const', dest='edge',
const=GPIO.RISING, help='respond to pin going up')
pgroup.add_argument('-a', '--edge-any', action='store_const', const=GPIO.BOTH,
dest='edge', help='respond to any pin change')
parser.add_argument('-b', '--debounce', type=int, default=200,
help='debounce period (in milliseconds, default=200)')
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parser.add_argument('-H', '--hold', type=int, default=-1,
help='optional hold time, pin must be held stable for the '
'specified time in milliseconds to trigger cmd')
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parser.add_argument('-t', '--timeout', type=int, default=-1,
help='optional timeout (in milliseconds) to wait')
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parser.add_argument('-i', '--ignore-result', action='store_true', default=False,
help='ignore command result code (default: exit if <> 0)')
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pgroup = parser.add_mutually_exclusive_group(required=False)
pgroup.add_argument('-c', '--continuous', default=False, action='store_true',
help='continously monitor GPIO pin and run cmd upon change')
pgroup.add_argument('-o', '--once', action='store_false', dest='continuous',
help='monitor pin and run cmd once, then exit (default)')
parser.add_argument('cmd', help='command to execute when pin goes low')
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parser.add_argument('arg', nargs='*', help='argument(s) for the command (*)')
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args = parser.parse_args() # parse command line
GPIO.setmode(args.mode) # set GPIO number mode
GPIO.setup(args.pin, GPIO.IN, pull_up_down=args.pull) # setup pin as input
if args.daemon and fork() != 0: # Fork for daemon mode
exit(0) # exit parent process
ret = 0
while args.ignore_result or ret == 0:
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# wait for GPIO pin to be changed in the right direction
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if GPIO.wait_for_edge(args.pin, args.edge, bouncetime=args.debounce,
timeout=args.timeout):
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state = GPIO.input(args.pin)
# pin changed, if required check if it is stays the same long enough
if (args.hold < 0) or (
GPIO.wait_for_edge(args.pin, GPIO.BOTH, bouncetime=args.debounce,
timeout=args.hold - args.debounce) is None):
ret = system(' '.join([ args.cmd ] + [
[ 'LOW', 'HIGH' ][state] if arg == '%STATE%' else
str(args.pin) if arg == '%PIN%' else arg for arg in args.arg]))
if not args.continuous: # exit if running once
break
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else: # exit if timeout
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ret = -1
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break
GPIO.cleanup(args.pin) # cleanup GPIO
exit(ret) # and return the result
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