This is how you can do it in python
#!/usr/bin/env python2.7
# script by Alex Eames http://RasPi.tv
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
# GPIO 23 & 24 set up as inputs. One pulled up, the other down.
# 23 will go to GND when button pressed and 24 will go to 3V3 (3.3V)
# this enables us to demonstrate both rising and falling edge detection
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(24, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
# now we'll define the threaded callback function
# this will run in another thread when our event is detected
def my_callback(channel):
print "Rising edge detected on port 24 - even though, in the main thread,"
print "we are still waiting for a falling edge - how cool?\n"
print "Make sure you have a button connected so that when pressed"
print "it will connect GPIO port 23 (pin 16) to GND (pin 6)\n"
print "You will also need a second button connected so that when pressed"
print "it will connect GPIO port 24 (pin 18) to 3V3 (pin 1)"
raw_input("Press Enter when ready\n>")
# The GPIO.add_event_detect() line below set things up so that
# when a rising edge is detected on port 24, regardless of whatever
# else is happening in the program, the function "my_callback" will be run
# It will happen even while the program is waiting for
# a falling edge on the other button.
GPIO.add_event_detect(24, GPIO.RISING, callback=my_callback)
try:
print "Waiting for falling edge on port 23"
GPIO.wait_for_edge(23, GPIO.FALLING)
print "Falling edge detected. Here endeth the second lesson."
except KeyboardInterrupt:
GPIO.cleanup() # clean up GPIO on CTRL+C exit
GPIO.cleanup() # clean up GPIO on normal exit
And here is a similar example with callbacks:
#!/usr/bin/env python2.7
# script by Alex Eames http://RasPi.tv
# http://RasPi.tv/how-to-use-interrupts-with-python-on-the-raspberry-pi-and-rpi-gpio-part-3
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
# GPIO 23 & 17 set up as inputs, pulled up to avoid false detection.
# Both ports are wired to connect to GND on button press.
# So we'll be setting up falling edge detection for both
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_UP)
# GPIO 24 set up as an input, pulled down, connected to 3V3 on button press
GPIO.setup(24, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
# now we'll define two threaded callback functions
# these will run in another thread when our events are detected
def my_callback(channel):
print "falling edge detected on 17"
def my_callback2(channel):
print "falling edge detected on 23"
print "Make sure you have a button connected so that when pressed"
print "it will connect GPIO port 23 (pin 16) to GND (pin 6)\n"
print "You will also need a second button connected so that when pressed"
print "it will connect GPIO port 24 (pin 18) to 3V3 (pin 1)\n"
print "You will also need a third button connected so that when pressed"
print "it will connect GPIO port 17 (pin 11) to GND (pin 14)"
raw_input("Press Enter when ready\n>")
# when a falling edge is detected on port 17, regardless of whatever
# else is happening in the program, the function my_callback will be run
GPIO.add_event_detect(17, GPIO.FALLING, callback=my_callback, bouncetime=300)
# when a falling edge is detected on port 23, regardless of whatever
# else is happening in the program, the function my_callback2 will be run
# 'bouncetime=300' includes the bounce control written into interrupts2a.py
GPIO.add_event_detect(23, GPIO.FALLING, callback=my_callback2, bouncetime=300)
try:
print "Waiting for rising edge on port 24"
GPIO.wait_for_edge(24, GPIO.RISING)
print "Rising edge detected on port 24. Here endeth the third lesson."
except KeyboardInterrupt:
GPIO.cleanup() # clean up GPIO on CTRL+C exit
GPIO.cleanup() # clean up GPIO on normal exit
