For Raspberry Pi model 2 and 3
It is unfortunate that each Raspberry Pi as more than one numbering scheme, and the numbers change/move around based on the version of the Pi. You specify in your Python code which numbering scheme you are using with the GPIO.setmode() command (see example code).
GPIO.setmode() has two acceptable values as follows:
import RPi.GPIO as GPIO # Set board pin numbering system GPIO.setmode(GPIO.BCM) # Setup each pin you use: whether it is input/output and if the default is on/off GPIO.setup(4, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) GPIO.setup(25, GPIO.OUT, initial=GPIO.LOW) GPIO.add_event_detect(4, GPIO.BOTH) def my_callback(): GPIO.output(25, GPIO.input(4)) GPIO.add_event_callback(4, my_callback)
val = GPIO( channel )
This will return either 0 / GPIO.LOW / False or 1 / GPIO.HIGH / True.
You can take a snapshot of an input at a moment in time:
if GPIO.input(channel): print('Input was HIGH') else: print('Input was LOW')
To wait for a button press by polling in a loop:
while GPIO.input(channel) == GPIO.LOW: time.sleep(0.01) # wait 10 ms to give CPU chance to do other things
GPIO.output( channel, state )
State can be 0 / GPIO.LOW / False or 1 / GPIO.HIGH / True.
To set an output high:
GPIO.output(12, GPIO.HIGH) # or GPIO.output(12, 1) # or GPIO.output(12, True)
To set an output low:
GPIO.output(12, GPIO.LOW) # or GPIO.output(12, 0) # or GPIO.output(12, False)
event_to_look_for can be:
GPIO.add_event_detect(channel, GPIO.RISING) # add rising edge detection on a channel do_something() if GPIO.event_detected(channel): print('Button pressed')
Setup a callback function to be executed whenever a value change is detected on an input pin.
def my_callback(channel): print('Callback!') GPIO.add_event_detect(channel, GPIO.RISING) GPIO.add_event_callback(channel, my_callback)
By returning all channels you have used back to inputs with no pull up/down, you can avoid accidental damage to your RPi by shorting out the pins. Note that this will only clean up GPIO channels that your script has used. Note that GPIO.cleanup() also clears the pin numbering system in use.
To discover information about your RPi:
To discover the Raspberry Pi board revision:
To discover the version of RPi.GPIO:
http://raspberry.io/projects/view/reading-and-writing-from-gpio-ports-from-python/ https://raspberrypi.stackexchange.com/questions/12966/what-is-the-difference-between-board-and-bcm-for-gpio-pin-numbering https://sourceforge.net/p/raspberry-gpio-python/wiki/BasicUsage/