RPIO 0.1.4

An extension of RPi.GPIO to easily use interrupts on the Raspberry Pi

RPIO extends RPi.GPIO with easy interrupt handling.

Interrupts are used to receive notifications from the kernel when GPIO state changes occur. Advantages include minimized cpu consumption, very fast notification times, and the ability to trigger on specific edge transitions (‘rising|falling|both’). This is an example of how to use RPIO:

import logging
logging.basicConfig(level=logging.DEBUG)
import RPIO

def do_something(gpio_id, value):
    print("New value for GPIO %s: %s" % (gpio_id, value))

RPIO.add_interrupt_callback(17, do_something, edge='rising')
RPIO.add_interrupt_callback(18, do_something, edge='falling')
RPIO.add_interrupt_callback(19, do_something, edge='both')
RPIO.wait_for_interrupts()

If you want to receive a callback inside a Thread (which won’t block anything else on the system), set threaded_callback to True when adding an interrupt- callback. Here is an example:

RPIO.add_interrupt_callback(17, do_something, edge='rising',
        threaded_callback=True)

Make sure to double-check the value returned from the interrupt, since it is not necessarily corresponding to the edge (eg. 0 may come in as value, even if edge=”rising”). To remove all callbacks from a certain gpio pin, use RPIO.del_interrupt_callback(gpio_id). To stop the wait_for_interrupts() loop you can either set RPIO.is_waiting_for_interrupts to False, or call RPIO.stop_waiting_for_interrupts().

If an interrupt occurs while your callback function does something blocking (like time.sleep() outside a thread), events will not arrive until you release the block. Only one process can receive interrupts for a specific GPIO pin, since the read on /sys/class/gpio/gpio<N>/value destroys the value for subsequent reads. RPIO uses epoll to receive interrupts from the kernel.

RPi.GPIO

You can use all of RPi.GPIO’s functionality through RPIO. Note that RPIO uses GPIO.BCM pin numbering by default

import RPIO

# set up GPIO output channel
RPIO.setup(17, RPIO.OUT)

# set gpio 17 to high
RPIO.output(17, RPIO.HIGH)

# set up output channel with an initial state
RPIO.setup(18, RPIO.OUT, initial=RPIO.LOW)

# set up input channel with pull-up control
#   (pull_up_down be PUD_OFF, PUD_UP or PUD_DOWN, default PUD_OFF)
RPIO.setup(19, RPIO.IN, pull_up_down=RPIO.PUD_UP)

# read input from gpio 19
input_value = RPIO.input(19)

# set up rising edge detection (EXPERIMENTAL)
set_rising_event(19)

# check for an event (EXPERIMENTAL)
if RPIO.event_detected(19):
    print('Rising edge detected!')

# set up falling edge detection (EXPERIMENTAL)
RPIO.set_rising_event(19, enable=False)  # disable rising edge detection (as set above)
RPIO.set_falling_event(19)

# set up high detection (EXPERIMENTAL)
RPIO.set_falling_event(19, enable=False)  # disable falling edge detection (as set above)
RPIO.set_high_event(19)

# set up low detection (EXPERIMENTAL)
RPIO.set_high_event(19, enable=False)  # disable high detection (as set above)
RPIO.set_low_event(19)

# to change to BCM RPIO numbering
RPIO.setmode(RPIO.BCM)

# to reset every channel that has been set up by this program to INPUT with no pullup/pulldown and no event detection
RPIO.cleanup()

Links

• https://github.com/metachris/raspberrypi-utils

• http://pypi.python.org/pypi/RPi.GPIO

• http://www.kernel.org/doc/Documentation/gpio.txt

Feedback

Chris Hager (<[e-mail]>)

License

RPIO is free software, released under the MIT license.

Copyright (c) 2013 Chris Hager <[e-mail]>

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.